CN109405937B - A wide range ratio water meter calibration standard device and water meter calibration method thereof - Google Patents

Abstract

The present invention discloses a wide-range ratio water meter calibration standard device for water meter calibration and a water meter calibration method. The wide-range ratio water meter calibration standard device provided by the present invention includes a piston-type device as a main standard and a peripheral system, a calibration device, a pressurizing system, a high-level water tank and an exhaust system. The present invention not only realizes the calibration of the water meter, but more importantly, by adopting a column-disc combined standard, the lower limit measurement capability of the calibration device is greatly improved, overcoming the difficulty that the device is difficult to provide small flow calibration of the water meter; in addition, the small flow back pressure system effectively overcomes the problem of abnormal operation caused by insufficient back pressure during small flow calibration of the water meter.

Description

A wide range ratio water meter calibration standard device and water meter calibration method thereof

Technical Field

The invention relates to a wide range ratio water meter calibration standard device for water meter calibration and a water meter calibration method.

Background technique

At present, the calibration devices used for water meter calibration are mainly static volumetric method or static mass method liquid flow standard devices. These two types of liquid flow standard devices meet the calibration requirements of water meters to a certain extent, but they also have obvious defects in use, mainly manifested as: (i) The static volumetric method liquid flow standard device has low efficiency in water meter calibration. Since the working measuring instrument of the static volumetric method liquid flow standard device is generally a gourd-shaped measuring instrument with a measuring neck. When the device water meter is used for flow calibration, the volume in the measuring instrument can only be read when the liquid reaches the measuring neck. Therefore, when the calibration flow is small, the calibration takes a long time, which is manifested as low calibration efficiency; (ii) The flow stabilization time is long. When the water meter is adjusted from one target flow point to another target flow point, the pressure in the corresponding pipeline will change accordingly. The change in the pressure in the pipeline will affect the change in the pressure in the pressure-stabilizing container, and the change in the pressure in the pressure-stabilizing container will affect the change in the amount of water supplied to the pressure-stabilizing container by the water pump. This change process requires a long adjustment time to stabilize the pressure in the pressure-stabilizing container within the constant pressure range, ensure the stability of the flow in the pipeline, and then realize the calibration of the water meter flow; (iii) The weighing scale in the static mass method liquid flow standard device is easily affected by the environment (such as vibration, temperature, humidity, etc.), and the environmental conditions are difficult to guarantee, especially the vibration of the water pump and the pipeline. Therefore, the weighing scale is easily affected by the environment and prone to zero drift, and the accuracy is difficult to guarantee; (iv) The static volume method or static mass method liquid flow standard device occupies a large space and is difficult to move once built. The liquid flow standard device used for calibrating the water meter flow generally requires compact equipment and small space, so the device is difficult to meet the requirements; (v) The static volume method or static mass method liquid flow standard device is not easy to save energy. Once the water pump is started, even if the water meter is replaced during the calibration period, the device will no longer stop, so the energy consumption is serious.

The patent number is: ZL 2011 1 0339915.1, and the patent name is: A water meter calibration device and a water meter calibration method, which discloses a water meter calibration device and a water meter calibration method. The timing and frequency counting devices of the water meter calibration device in the invention are respectively connected to the corresponding photoelectric sampler and the pulse control circuit of the servo motor; the protective sleeve is fixedly connected to the cylinder body of the hydraulic cylinder, the servo motor is fixed on the protective sleeve, the rotating shaft of the servo motor is fixedly connected to one end of the lead screw through a coupling, the other end of the lead screw is connected to the lead screw nut, and the lead screw nut is connected to one end of the piston of the hydraulic cylinder; the hydraulic cylinder is provided with a cylinder body water inlet and a cylinder body water outlet, the water tank is provided with a water tank water inlet and a water tank water outlet, the cylinder body water inlet is connected to the water tank water outlet through a first water inlet pipe, and a water outlet pipe is installed at the cylinder body water outlet; a second water inlet pipe is installed at the water tank water inlet, and switch valves are installed on the first water inlet pipe, the second water inlet pipe and the water outlet pipe. The device of the invention has the following shortcomings when used for water meter calibration: (i) It is impossible to achieve a wide range ratio of flow output. Only the cylinder body is used as the volume standard, and the piston is used to cooperate with the cylinder body. The water in the cylinder body is discharged from the cylinder body by the movement of the piston, and flows through the water meter to be tested at a certain flow rate in the outlet pipe to achieve the calibration of the water meter to be tested; because the horizontal movement of the piston is converted by the rotation of the servo motor through the cooperation of the lead screw and the lead screw nut, when the flow rate is small, the lead screw needs to rotate at a low angular velocity to push the piston to run slowly, and the rotation of the lead screw is driven by the servo motor, so the servo motor must rotate at a low angular velocity to provide the lead screw with a low rotation angular velocity. However, the servo motor will creep at a low rotation speed, causing the entire piston system to run unstably, so this type of piston cannot provide a small flow rate; therefore, under the premise that the maximum flow rate that this type of piston can provide is certain, since this type of piston can only provide a large flow rate and cannot provide a small flow rate, the ratio of the maximum and minimum flow rates that this type of piston can provide is small, so a wide range ratio cannot be achieved. (ii) Under low flow conditions, it is impossible to provide sufficient back pressure downstream of the water meter to be tested. When calibrating the water meter under test, in order to ensure that the water meter under test can work normally, it is necessary to provide sufficient back pressure downstream of the water meter under test. At low flow rates, due to the small water flow loss in the pipe downstream of the water meter under test, the height of the downstream back pressure pipe is generally not more than 2m due to the height limit of the factory building or laboratory (the height of the calibration table is generally 1m). The back pressure formed by the back pressure pipe of this height downstream of the water meter plus the back pressure formed downstream of the water meter under test when the water flows in the pipe downstream of the water meter under test to overcome the pressure loss of the pipe is not enough to provide sufficient back pressure to the water meter under test. Therefore, at low flow rates, due to the inability to provide sufficient back pressure to the water meter under test, it is easy to cause the water meter under test to malfunction, which brings difficulties to the calibration of the water meter under test.

The patent number is: ZL 2016 1 0120739.1, and the patent name is: A standard device and calibration method for constant flow valve flow and differential pressure calibration, which discloses a standard device and calibration method for constant flow valve flow and differential pressure calibration. The stepper motor of the constant flow valve flow and differential pressure calibration standard device in the invention is fixed on the reducer, the rotating shaft of the stepper motor is connected to the input shaft sleeve of the reducer, the output shaft of the reducer is fixedly connected to the end of one end of the screw through a coupling, and a screw sleeve is installed behind the end of one end of the screw and close to the end and the other end of the screw, and a screw nut is installed on the screw between the screw sleeves, and the screw nut is fixed in the middle of the slidable metal support, the lower end of the slidable metal support is connected to the linear guide rail, and the upper part of the slidable metal support is equipped with a floating joint, which is fixedly connected to the cylindrical piston in the hydraulic cylinder, and a Y-type sealing ring is installed between the cylindrical piston and the hydraulic cylinder; a grating ruler is installed on the inner side of the linear guide rail in the invention, and the photoelectric reading head of the grating ruler is fixedly connected to the slidable metal support; the hydraulic cylinder in the invention is provided with a cylinder exhaust calibration port, and the cylinder The exhaust calibration port of the hydraulic cylinder is fixedly connected to one end of the manual switch ball valve through a stainless steel pipe, the other end of the manual switch ball valve is fixedly connected to one end of the back pressure pipe, the other end of the back pressure pipe is fixedly connected to the nozzle, and the water inlet of the hydraulic cylinder is connected to the water tank through the cylinder water inlet switch ball valve; the water outlet of the hydraulic cylinder is connected to one end of the cylinder water outlet switch ball valve, the other end of the cylinder water outlet switch ball valve is connected to the front straight pipe section through a three-way pipe and the clamp meter front switch ball valve, the other end of the cylinder water outlet switch ball valve is connected to the exhaust water pump through a three-way pipe and the exhaust water pump rear switch ball valve, and the exhaust water pump front switch ball valve is arranged on the air outlet of the exhaust water pump; a constant flow valve to be calibrated is arranged between the front straight pipe section and the rear straight pipe section, and differential pressure transmitters are connected in parallel at both ends of the constant flow valve, the rear straight pipe section is connected to the indicating flowmeter through the indicating flowmeter front switch ball valve, and the indicating flowmeter is connected to the water tank. Similar to the invention patent with patent number: ZL 20111 0339915.1, patent name: A water meter calibration device and a water meter calibration method, the device of the invention has the following shortcomings when used for flow and differential pressure calibration of a constant flow valve: (i) It is impossible to achieve a wide range ratio of flow output. The device of the invention only uses the cylindrical piston as the volume standard, and adopts the cooperation between the cylindrical piston and the hydraulic cylinder. The water in the hydraulic cylinder is discharged from the hydraulic cylinder by the movement of the cylindrical piston, and flows through the constant flow valve at a certain flow rate in the front and rear straight pipe sections, so as to realize the flow and differential pressure calibration of the constant flow valve under inspection; since the horizontal movement of the cylindrical piston is converted by the rotation of the stepper motor through the cooperation of the lead screw and the lead screw nut, when the flow rate is small, the lead screw needs to push the cylindrical piston to move slowly at a low rotation angular velocity, and the rotation of the lead screw is driven by the stepper motor, so the stepper motor must be at a low rotation angular velocity to provide the lead screw with a low rotation angular velocity. However, the stepper motor will have a creeping phenomenon at a low rotation speed, causing the entire piston system to run unstably, so this type of piston cannot provide a small flow rate; therefore, under the premise that the maximum flow rate that this type of piston can provide is certain, since this type of piston can only provide a large flow rate but cannot provide a small flow rate, the ratio between the maximum and minimum flow rates that this type of piston can provide is small, and thus a wide range ratio cannot be achieved. (ii) Under the condition of small flow rate, sufficient back pressure cannot be provided downstream of the constant flow valve. When calibrating the constant flow valve to be tested, sufficient back pressure must be provided downstream of the constant flow valve to be tested. At low flow rates, due to the small water flow loss in the pipeline downstream of the constant flow valve to be tested, the height of the downstream back pressure pipe is generally not more than 2m due to the height limit of the factory building or laboratory (the height of the calibration table is generally 1m). The back pressure formed by the back pressure pipe of this height downstream of the constant flow valve plus the back pressure formed downstream of the constant flow valve to overcome the pressure loss of the pipeline when the water flows in the pipeline downstream of the constant flow valve to be tested is not enough to provide sufficient back pressure to the constant flow valve to be tested. Therefore, at low flow rates, due to the inability to provide sufficient back pressure to the constant flow valve to be tested, it is easy to cause the constant flow valve to be tested to malfunction, which brings difficulties to the calibration of the constant flow valve to be tested.

In summary, due to the many defects of the static volume method or static mass method liquid flow standard device and the patent numbers are: ZL 2011 1 0339915.1, ZL 2016 1 0120739.1, and the corresponding patent names are: a water meter calibration device and a water meter calibration method, a constant flow valve flow and differential pressure calibration standard device and a calibration method, there is an urgent need for a new type of wide range ratio liquid flow standard (or water meter calibration) device to replace the current static volume method, static mass method or patent numbers: ZL 2011 1 0339915.1, ZL 2016 10120739.1 invented liquid flow standard device.

Summary of the invention

The purpose of the present invention is to provide a column-disk combined type wide range ratio piston type water meter calibration device for water meter calibration and a method for calibrating a water meter using the device.

To achieve the above purpose, the technical solution adopted by the present invention is: the provided wide range ratio water meter calibration standard device includes a piston device as a main standard and a peripheral system, a calibration device, a pressurizing system, a high-level water tank and an exhaust system. The piston device and peripheral systems serving as the main standard include a servo motor, a reducer, a reducer metal support, a coupling, a front metal support of the screw, a screw, a linear guide, a piston metal bracket, a slidable metal support, a screw nut, a floating joint, a cylindrical piston, a front cylinder water inlet switch ball valve, a front cylinder water inlet pipe, a front cylinder exhaust pipe, a front cylinder manual exhaust ball valve, a piston cylinder front flange, a piston cylinder, a front cylinder water outlet pipe, a front cylinder water outlet switch ball valve, a screw rear metal support, a piston metal support, a disc piston, a piston cylinder rear flange, a rear cylinder manual exhaust ball valve, a rear cylinder exhaust pipe, a rear cylinder water inlet pipe, a rear cylinder water inlet switch ball valve, a rear cylinder water outlet pipe, a rear cylinder water outlet switch ball valve, front and rear cylinder water outlet pipe isolation ball valves, and a front and rear cylinder water outlet pipe isolation ball valve connecting pipe. The calibration device includes a switch ball valve in front of the meter clamp, a connecting pipe in front of the meter clamp, a meter clamp, a front straight pipe section, an electromechanical conversion device for the water meter to be tested, a water meter to be tested, a rear straight pipe section, a calibration device support frame, a manifold, a small-diameter back-pressure switch ball valve, a back-pressure switch ball valve with the same diameter, a small-diameter back-pressure pipe, and a back-pressure pipe with the same diameter. The pressurization system includes a pressure water pump outlet pipe, a switch ball valve after the pressure water pump, a pressure water pump, a switch ball valve in front of the pressure water pump, and a pressure water pump inlet pipe; the pressure water pump outlet pipe is fixedly connected to the small-diameter back-pressure pipe through a tee pipe. The exhaust system includes an exhaust water inlet pipe, a switch ball valve in front of the exhaust water pump, an exhaust water pump, a switch ball valve after the exhaust water pump, and an exhaust water outlet pipe.

The piston type device and peripheral system use a servo motor as a driving device, the servo motor is fixed on the reducer, the servo motor is fixedly installed on the reducer housing, the reducer is fixedly installed on the reducer metal support, the reducer metal support is fixedly installed on the piston metal bracket, the rotating shaft of the servo motor is connected to the input shaft sleeve of the reducer, the output shaft of the reducer is fixedly connected to the front end of one end of the screw through a coupling, a screw sleeve is installed between the end of one end of the screw and the screw thread and between the end of the other end of the screw and the screw thread, a screw nut is installed on the screw between the screw sleeves, the screw nut is fixed in the middle of the slidable metal support, the lower end of the slidable metal support is connected to the linear guide, the upper part of the slidable metal support is equipped with a floating joint, the floating joint is fixedly connected to one end of the cylindrical piston in the piston cylinder, a certain water-filled gap is left between the cylindrical piston and the piston cylinder, a Y-type sealing ring is used to seal between the cylindrical piston and the front flange of the piston cylinder, and the Y-type sealing ring is used to seal The sealing ring is fixedly installed on the front flange of the piston cylinder, and the front flange of the piston cylinder is fixedly installed on the front end of the piston cylinder. An O-ring is used to seal the piston cylinder and the front flange of the piston cylinder; the other end of the cylindrical piston is fixedly connected to the disc piston installed in the piston cylinder, and a Y-ring and a guide ring are installed between the disc piston and the piston cylinder. The rear flange of the piston cylinder is fixedly installed on the rear end of the piston cylinder, and an O-ring is used to seal the piston cylinder and the rear flange of the piston cylinder. The screw sleeve and the piston cylinder are fixedly installed on their respective corresponding metal supports; the front flange of the piston cylinder is provided with a front cylinder exhaust calibration port, a front cylinder water inlet and a front cylinder water outlet; the front cylinder exhaust calibration port is fixedly connected to one end of the front cylinder manual exhaust ball valve through the front cylinder exhaust connecting pipe, and the other end of the front cylinder manual exhaust ball valve is fixedly connected to one end of the front cylinder exhaust pipe. The front cylinder exhaust pipe is a rigid pipe with a certain height (a certain distance higher than the horizontal piston cylinder), and the other end of the front cylinder exhaust pipe is a water outlet The water inlet of the front cylinder body is fixedly connected to one end of the front cylinder body water inlet switch ball valve through the front cylinder body water inlet connecting pipe, and the other end of the front cylinder body water inlet switch ball valve is fixedly connected to one end of the front cylinder body water inlet pipe, and the other end of the front cylinder body water inlet pipe is fixedly connected to the front cylinder body water supply port on the high-level water tank; the front cylinder body water outlet is fixedly connected to one end of the front cylinder body water outlet switch ball valve through the front cylinder body water outlet connecting pipe, and the other end of the front cylinder body water outlet switch ball valve is fixedly connected to one end of the front cylinder body water outlet pipe, and the other end of the front cylinder body water outlet pipe is fixedly connected to one end of the front and rear cylinder body water outlet pipe isolation ball valve, and the other end of the front and rear cylinder body water outlet pipe isolation ball valve connecting pipe is fixedly connected to one end of the front and rear cylinder body water outlet pipe isolation ball valve connecting pipe, and the other end of the front and rear cylinder body water outlet pipe isolation ball valve connecting pipe is fixedly connected to the exhaust water pump outlet pipe through a T-shaped tee; the rear cylinder body exhaust calibration port, the rear cylinder body water inlet and the rear cylinder body water outlet are provided on the rear flange of the piston cylinder; the rear cylinder body exhaust The gas calibration port is fixedly connected to one end of the manual exhaust ball valve of the rear cylinder through the rear cylinder exhaust connecting pipe, and the other end of the manual exhaust ball valve of the rear cylinder is fixedly connected to one end of the exhaust pipe of the rear cylinder; the exhaust pipe of the rear cylinder is a rigid pipe with a certain height (a certain distance higher than the piston cylinder (the piston cylinder is a horizontal piston cylinder)), and the other end of the exhaust pipe of the rear cylinder is an inverted U-shaped pipe with a water outlet downward; the water inlet of the rear cylinder is fixedly connected to one end of the water inlet switch ball valve of the rear cylinder through the water inlet connecting pipe of the rear cylinder, the other end of the water inlet switch ball valve of the rear cylinder is fixedly connected to one end of the water inlet pipe of the rear cylinder, and the other end of the water inlet pipe of the rear cylinder is fixedly connected to the water supply port of the rear cylinder on the high-level water tank; the water outlet of the rear cylinder is fixedly connected to one end of the water outlet switch ball valve of the rear cylinder through the water outlet connecting pipe of the rear cylinder, the other end of the water outlet switch ball valve of the rear cylinder is fixedly connected to one end of the water outlet pipe of the rear cylinder, and the other end of the water outlet pipe of the rear cylinder is fixedly connected to one end of the switch ball valve in front of the meter clamp. The meter clamp of the calibration device is fixedly installed at the front end of the calibration device support frame, the water inlet end of the meter clamp is fixedly connected to the other end of the switch ball valve in front of the meter clamp through the front connecting pipe of the meter clamp, the water outlet end of the meter clamp is connected to one end of the front straight pipe section, the front straight pipe section is connected to the water inlet end of the water meter to be inspected, the water outlet end of the water meter to be inspected is fixedly connected to one end of the rear straight pipe section, the other end of the rear straight pipe section is fixedly connected to one end of a manifold with the same diameter, the other end of the manifold with the same diameter is fixedly connected to one end of an elbow, the other end of the elbow is fixedly connected to one end of a back-pressure connecting pipe with the same diameter extending vertically upward, the other end of the back-pressure connecting pipe with the same diameter is fixedly connected to one end of a back-pressure switch ball valve with the same diameter, the other end of the back-pressure switch ball valve with the same diameter is fixedly connected to one end of a back-pressure pipe with the same diameter, and the other end of the back-pressure pipe with the same diameter is fixedly connected to the same The water outlet of the full-diameter back-pressure pipe is fixedly connected; the manifold is fixedly installed at the end of the support frame of the calibration device, and a water outlet hole is opened on the outer wall vertically upward in the middle position of the manifold (the inner diameter of the water outlet hole is not greater than DN15), one end of a small-diameter back-pressure connecting pipe with the same inner diameter as the water outlet hole is connected to the water outlet hole and fixed on the outer wall of the manifold around the water outlet hole, the other end of the small-diameter back-pressure connecting pipe is fixedly connected to one end of the small-diameter back-pressure switching ball valve, the other end of the small-diameter back-pressure switching ball valve is fixedly connected to one end of the small-diameter back-pressure pipe, and the other end of the small-diameter back-pressure pipe is fixedly connected to the water outlet of the small-diameter back-pressure pipe on the high-level water tank; a T-type tee is installed in the middle position of the small-diameter back-pressure pipe, and the two opposite pipe openings of the T-type tee are fixed in series with the small-diameter back-pressure pipe, and the other pipe opening of the T-type tee is fixedly connected to the other end of the water pump outlet pipe. The water inlet of the pressurized water pump of the pressurized system is fixedly connected to one end of the water inlet connecting pipe of the pressurized water pump, the other end of the water inlet connecting pipe of the pressurized water pump is fixedly connected to one end of the switch ball valve in front of the pressurized water pump, the other end of the switch ball valve in front of the pressurized water pump is fixedly connected to one end of the water inlet pipe of the pressurized water pump, and the other end of the water inlet pipe of the pressurized water pump is fixedly connected to the water supply port of the pressurized water pump of the high-level water tank; the water outlet of the pressurized water pump is fixedly connected to one end of the water outlet connecting pipe of the pressurized water pump, the other end of the water outlet connecting pipe of the pressurized water pump is fixedly connected to one end of the switch ball valve behind the pressurized water pump, the other end of the switch ball valve behind the pressurized water pump is fixedly connected to one end of the water outlet pipe of the pressurized water pump, and the other end of the water outlet pipe of the pressurized water pump is fixedly connected to the other pipe opening of the T-type three-way. The high-level water tank is placed at a position higher than the horizontal piston, and is provided with a front cylinder water supply port, a rear cylinder water supply port, a water pump water supply port, a small-diameter back pressure pipe water outlet, and a back pressure pipe water outlet of the same diameter. The high-level water tank is a square water tank, the net height inside the water tank is not less than 0.7m, the water level inside the water tank is not less than 0.5m, and the bottom of the high-level water tank is higher than the piston cylinder. One end of the exhaust water inlet pipe of the exhaust system is fixedly connected to the high-level water tank, the water inlet at one end of the exhaust water inlet pipe is located in the high-level water tank, the other end of the exhaust water inlet pipe is fixedly connected to one end of the exhaust water pump front switch ball valve, the other end of the exhaust water pump front switch ball valve is fixedly connected to one end of the exhaust water pump front connecting pipe, the other end of the exhaust water pump front connecting pipe is fixedly connected to the water inlet of the exhaust water pump, the water outlet of the exhaust water pump is fixedly connected to one end of the exhaust water pump rear connecting pipe, the other end of the exhaust water pump rear connecting pipe is fixedly connected to one end of the exhaust water pump rear switch ball valve, the other end of the exhaust water pump rear switch ball valve is fixedly connected to one end of the exhaust water pump outlet pipe, the other end of the exhaust water pump outlet pipe is fixedly connected to the high-level water tank, and the water outlet at the other end of the exhaust water pump outlet pipe is located in the high-level water tank.

Furthermore, the servo motor described in the present invention is replaced by a stepper motor.

When the water meter calibration device is used to calibrate the small flow of the water meter, the method for generating back pressure in the rear straight pipe section downstream of the water meter to be tested comprises the following steps and principles:

i) While controlling the rotation speed to correspond to the small flow point of the water meter to be calibrated, open the ball valve before turning on the booster pump and start the booster pump.

ii) Under the action of the booster water pump, the water in the high-level water tank passes through the booster water pump inlet pipe, the booster water pump front switch ball valve, the booster water pump, the booster water pump rear switch ball valve, the booster water pump outlet pipe, and then enters the small-diameter back-pressure pipe, and finally flows into the high-level water tank from the small-diameter back-pressure pipe.

iii) When the water supplied by the booster pump flows into the high-level water tank through the small-diameter back-pressure pipe, the water flow will quickly generate a back pressure in the small-diameter back-pressure pipe that exceeds the minimum back pressure required for calibrating the water meter being tested due to the pressure loss in the pipe. The back pressure is transmitted to the water meter being tested through the rear straight pipe section.

iv) The start-up of the booster pump is synchronized with the reverse acceleration control of the servo motor when verifying the small flow point of the water meter under test, and the flow stabilization time of the water flow supplied by the booster pump and the time for the servo motor to reversely accelerate to a constant speed corresponding to the flow point of the water meter under test are both short. The two can reach the flow balance point in a short time, that is, the small flow verification back pressure system can establish a constant and sufficient back pressure for the water meter under test in a short time.

The method for calibrating a water meter using the above water meter calibration device of the present invention comprises the following steps:

A. Calibration of large flow points

a) Install the water meter to be tested between the front straight pipe section and the rear straight pipe section.

b) Execute step 9), control the servo motor to rotate in the opposite direction to drive the reducer to rotate in the same direction, the rotation of the servo motor is reduced by the reducer to drive the lead screw to rotate in the opposite direction, the reverse rotation of the lead screw is converted into the reverse horizontal movement of the lead screw nut through the cooperation of the lead screw and the lead screw nut, the reverse horizontal movement of the lead screw nut drives the slidable metal support to move in the opposite synchronous horizontal direction, the reverse synchronous horizontal movement of the slidable metal support drives the floating joint to move in the opposite synchronous horizontal direction, the reverse synchronous horizontal movement of the floating joint pulls the cylindrical piston and the disc piston to move in the opposite synchronous horizontal direction until the other end of the cylindrical piston and the disc piston reach the top of the piston cylinder.

c) Close the isolation ball valves of the front and rear cylinder water outlet pipes and the switch ball valve of the rear cylinder water outlet; open the switch ball valve in front of the meter clamp, the small-diameter back pressure switch ball valve, the same-diameter back pressure switch ball valve, the switch ball valve in front of the exhaust water pump and the switch ball valve in the back of the exhaust water pump, start the exhaust water pump to remove the air from the rear cylinder water outlet pipe, the switch ball valve in front of the meter clamp, the connecting pipe in front of the meter clamp, the meter clamp, the front straight pipe section, the water meter to be inspected, the rear straight pipe section, the manifold, the small-diameter back pressure switch ball valve, the same-diameter back pressure switch ball valve, the small-diameter back pressure pipe, the same-diameter back pressure pipe, the exhaust water inlet pipe, the switch ball valve in front of the exhaust water pump, the exhaust water pump, and the exhaust water outlet pipe.

d) Close the front cylinder manual exhaust ball valve, the front cylinder water outlet switch ball valve, the front and rear cylinder water outlet pipe isolation ball valves, the rear cylinder manual exhaust ball valve, the rear cylinder water inlet switch ball valve, the exhaust water pump rear switch ball valve, and the small-diameter back pressure switch ball valve; open the front cylinder water inlet switch ball valve, the rear cylinder water outlet switch ball valve, the meter clamp front switch ball valve, and the same-diameter back pressure switch ball valve.

e) Control the servo motor to accelerate forward to a speed corresponding to the required calibration flow rate and then maintain a uniform rotation. At the same time, the forward rotation of the servo motor is decelerated by a certain reduction ratio of the reducer to drive the lead screw to rotate forward, and the rotation of the lead screw is converted into horizontal movement of the columnar piston and the disc piston through the cooperation between the lead screw and the lead screw nut, the slidable metal support, the floating joint, the columnar piston and the disc piston. The horizontal movement of the columnar piston and the disc piston draws water from the high-level water tank through the front cylinder water inlet pipe and the front cylinder water inlet switch ball valve into the space between the front flange of the piston cylinder, the columnar piston and the disc piston in the piston cylinder to fill the water. On the other hand, the water in the water-filled space between the rear flange of the piston cylinder and the disc-shaped piston is discharged outward through the rear cylinder water outlet switch ball valve and the rear cylinder water outlet pipe at the required calibration flow rate under the push of the disc-shaped piston, and enters the high-level water tank after passing through the switch ball valve in front of the meter clamp, the connecting pipe in front of the meter clamp, the meter clamp, the front straight pipe section, the water meter to be inspected, the rear straight pipe section, the manifold, the back pressure switch ball valve with the same diameter, and the back pressure pipe with the same diameter; after the cylindrical piston and the disc-shaped piston are converted from accelerated horizontal movement to uniform horizontal movement accordingly, the time frequency recorder begins to accumulate the frequency of the servo motor, and records the frequency accumulation start time t ₁ ; after the cylindrical piston and the disc piston change from accelerated horizontal movement to uniform horizontal movement respectively, the time-frequency recorder starts to accumulate the frequency signal of the output of the water meter under test, and records the frequency accumulation start time _t'1 ; when the accumulation of the frequency signal of the output of the water meter under test by the time-frequency recorder reaches the minimum number of frequency signals, the time-frequency recorder stops accumulating the frequency signal of the output of the water meter under test, and records the accumulation stop time _t'2 and the accumulated number of frequency signals N'; after the time-frequency recorder stops accumulating the frequency signal of the output of the water meter under test, the time-frequency recorder then stops accumulating the frequency signal of the output of the water meter under test, and records the accumulation stop time _t2 and the accumulated number of frequency signals N.

f) According to the cumulative number N' of the frequency signals of the water meter under test recorded by the time frequency recorder and the corresponding cumulative start time _t'1 and end time _t'2 , the average flow rate of the water meter under test during the frequency signal accumulation period is calculated according to formula (1):

Q＝(P×N')/( _t'2 - _t'1 ) (1)

Wherein, Q is the average flow rate during the time period of accumulating the frequency signals output by the inspected water meter; P is the cumulative amount of water represented by each frequency signal when water flows through the inspected water meter.

g) According to the cumulative number N of the servo motor frequency signals recorded by the time frequency recorder and the corresponding cumulative start time _t1 and end time _t2 , the average flow rate of the water meter calibration standard device within the frequency signal accumulation time period is calculated according to formula (2):

q＝πD ² ipωN/[4(t ₂ -t ₁ )] (2)

Wherein, q is the average flow rate of the water meter calibration standard device within the frequency signal accumulation time period; π is the pi; D is the inner diameter of the piston cylinder; i is the speed ratio of the reducer; p is the lead of the screw; ω is the angle of rotation of the rotating shaft of the servo motor (1) when the servo motor (1) receives each frequency signal.

h) According to formula (3), the indication error of the inspected flow point of the inspected water meter (37) is calculated as follows:

E＝(Q-q)/q×100％ (3)

Where E is the indication error of the inspected flow point of the inspected water meter.

i) judging whether the servo motor can continue to rotate in the same direction according to the next calibration flow point of the water meter under inspection, its calibration time and the distance that the disc-shaped piston has moved horizontally: if it can continue to rotate in the same direction, repeating steps e) to h) to complete the calibration of the next flow point; if it can no longer continue to rotate in the same direction, first executing step b), and then executing steps d) to h) to complete the calibration of the next flow point;

j) Repeat step i) to complete the calibration of other large flow points of the water meter being tested.

B. Calibration of small flow points

a') judging whether the servo motor can make reverse rotation according to the small flow verification flow point of the water meter under inspection, its verification time and the distance that the disc-shaped piston has moved horizontally: if it can make reverse rotation, executing steps c') to g'); if it cannot make reverse rotation, executing step b), and then executing steps c') to g');

b') Repeat step a') to complete the calibration of other small flow points of the water meter being tested.

c') Close the manual exhaust ball valve of the front cylinder, the water inlet switch ball valve of the front cylinder, the manual exhaust ball valve of the rear cylinder, the water outlet switch ball valve of the rear cylinder, the back pressure switch ball valve of the same diameter, and the exhaust water pump rear switch ball valve; open the water outlet switch ball valve of the front cylinder, the water inlet switch ball valve of the rear cylinder, the isolation ball valve of the front and rear cylinder outlet pipes, the small-diameter back pressure switch ball valve, the pressure water pump rear switch ball valve, and the pressure water pump front switch ball valve;

d') Control the servo motor to accelerate in the reverse direction to a speed corresponding to the required calibration flow rate and then maintain a uniform speed rotation. At the same time, the reverse rotation of the servo motor is decelerated by a certain reduction ratio of the reducer to drive the lead screw to rotate in the reverse direction, and the rotation of the lead screw is converted into horizontal movement of the column piston and the disc piston through the cooperation between the lead screw and the lead screw nut, the slidable metal support, the floating joint, the column piston and the disc piston. The horizontal movement of the column piston and the disc piston, on the one hand, sucks the water in the high-level water tank through the rear cylinder water inlet pipe and the rear cylinder water inlet switch ball valve into the water-filled space between the rear flange of the piston cylinder and the disc piston. On the other hand, the water in the water-filled space between the front flange of the piston cylinder, the column piston and the disc piston in the piston cylinder is pushed by the disc piston to be discharged outward at the required calibration flow rate through the front cylinder water outlet switch ball valve, the front cylinder water outlet pipe, and the front and rear cylinder water outlet pipe isolation ball valves, and passes through the switch ball valve in front of the meter clamp, the connecting pipe in front of the meter clamp, the meter clamp, the front straight pipe section, The water meter under test, the rear straight pipe section, the manifold, the small-diameter back-pressure switch ball valve, and the small-diameter back-pressure pipe enter the high-level water tank; while controlling the servo motor to accelerate in the reverse direction, start the booster pump. Under the action of the booster pump, the water in the high-level water tank enters the small-diameter back-pressure pipe through the booster pump inlet pipe, the switch ball valve in front of the booster pump, the booster pump, the switch ball valve after the booster pump, and the outlet pipe of the booster pump, and finally flows into the high-level water tank through the small-diameter back-pressure pipe. When the water flow supplied by the booster pump flows into the high-level water tank through the small-diameter back-pressure pipe, the water flow in the small-diameter back-pressure pipe will quickly generate a back pressure exceeding the minimum back pressure required for the calibration of the water meter under test. The back pressure is transmitted to the water meter under test through the rear straight pipe section, and finally quickly generates a constant back pressure exceeding the minimum back pressure required for the water meter under test in the rear straight pipe section; after a constant back pressure exceeding the minimum back pressure required for the water meter under test is generated in the rear straight pipe section, the time frequency recorder starts to accumulate the frequency of the servo motor, and records the frequency accumulation start time t ₁ ; After the time-frequency recorder starts to accumulate the frequency of the drive servo motor, the time-frequency recorder starts to accumulate the frequency signal of the output of the water meter under test, and records the frequency accumulation start time _t'1 ; When the time-frequency recorder accumulates the frequency signal of the output of the water meter under test to the minimum number of frequency signals, the time-frequency recorder stops accumulating the frequency signal of the output of the water meter under test, and records the accumulation stop time _t'2 and the accumulated number of frequency signals N'; After the time-frequency recorder stops accumulating the frequency signal of the output of the water meter under test, the time-frequency recorder then stops accumulating the frequency signal of the output of the water meter under test, and records the accumulation stop time _t2 and the accumulated number of frequency signals N;

e') executing step f);

f') According to the cumulative number N of the frequency signals of the servo motor (1) recorded by the time frequency recorder and the corresponding cumulative start time _t1 and end time _t2 , the average flow rate of the water meter calibration standard device within the frequency signal accumulation time period is calculated according to formula (4):

q＝πipωN(D ² -D ₁ ² )/[4(t ₂ -t ₁ )] (4)

Wherein, q is the average flow rate of the water meter calibration standard device within the frequency signal accumulation period; π is the pi; i is the speed ratio of the reducer; p is the lead of the screw; ω is the angle of the servo motor shaft when the servo motor receives each frequency signal; D is the inner diameter of the piston cylinder; _D1 is the outer diameter of the cylindrical piston.

g') execute step h).

The beneficial effects of the present invention are as follows: i) a piston-type device of a double standard combined with a column and a disk is used as the main standard of the water meter calibration device: the column piston, the disk piston and the piston cylinder together form a column-disk combined standard, which is used to provide a small flow rate during water meter calibration; the disk piston and the piston cylinder together form a disk-shaped standard, which is used to provide a large flow rate during water meter calibration. Since the water-filled space inside the column-disk combined standard is smaller than the water-filled space inside the disk-shaped standard, when the column piston and the disk piston move toward the front flange direction of the piston cylinder (called the top of the piston cylinder) for a certain distance, the volume of water discharged from the piston cylinder by the water-filled space being compressed is much smaller than when the disk piston moves toward the rear flange direction of the piston cylinder (called the bottom of the piston cylinder (18)) for the same distance, the volume of water discharged from the piston cylinder by the water-filled space being compressed is greatly reduced, so the column-disk combined standard can provide the small flow rate required for water meter calibration. ii) a small flow rate calibration back pressure system is used to generate sufficient back pressure downstream of the water meter being tested during small flow rate calibration, which effectively solves the problem of abnormal operation caused by insufficient back pressure during small flow rate calibration of the water meter.

The device and method for water meter calibration of the present invention not only realize the calibration of the water meter, but more importantly, by adopting a column-disc combined standard device, the lower limit measurement capability of the calibration device is greatly improved, and the difficult problem that the device is difficult to provide small flow calibration of the water meter is overcome; in addition, the small flow back pressure system effectively overcomes the problem of abnormal operation caused by insufficient back pressure during small flow calibration of the water meter.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a standard device for water meter calibration.

Detailed ways

The present invention analyzes the many limitations of traditional static volume method, static mass method and existing piston-type liquid flow standard devices when used for water meter calibration, and combines the development trend of new technologies of liquid flow standard devices to propose a novel column-disc piston-type water meter calibration device for water meter calibration, thereby realizing rapid calibration of water meters.

The design idea of the present invention: by summarizing the shortcomings of the invention patents of: ZL 2011 1 0339915.1, ZL 2016 10120739.1, and the corresponding patent names are: a water meter calibration device and a water meter calibration method, a standard device for constant flow valve flow and differential pressure calibration and a calibration method, a column-disc combined standard device is proposed to overcome the difficulty of the device in providing small flow calibration of the water meter and improve the ability of the calibration device to measure the lower limit flow. At the same time, a small flow back pressure system is used to generate sufficient back pressure downstream of the water meter being tested during small flow calibration, and the problem of abnormal operation caused by insufficient back pressure during small flow calibration of the water meter is solved.

As shown in FIG1 , the water meter calibration device of the present invention includes a piston device as a main standard and a peripheral system, a calibration device, a pressurizing system, a high-level water tank 50) and an exhaust system. The piston device as a main standard and the peripheral system include a servo motor 1), a reducer 2), a reducer metal support 3), a coupling 4), a front metal support of the screw 5), a screw 6), a linear guide 7), a piston metal bracket 8), a slidable metal support 9), a screw nut 10), a floating joint 11), a cylindrical piston 12), a front cylinder water inlet switch ball valve 13), a front cylinder water inlet pipe 14), a front cylinder exhaust pipe 15), a front cylinder manual exhaust ball valve 16), a piston cylinder front flange 17), a piston Cylinder 18), front cylinder water outlet pipe 19), front cylinder water outlet switch ball valve 20), screw rear metal support 21), piston metal support 22), disc piston 23), piston cylinder rear flange 24), rear cylinder manual exhaust ball valve 25), rear cylinder exhaust pipe 26), rear cylinder water inlet pipe 27), rear cylinder water inlet switch ball valve 28), rear cylinder water outlet pipe 29), rear cylinder water outlet switch ball valve 30), front and rear cylinder water outlet pipe isolation ball valve 31), front and rear cylinder water outlet pipe isolation ball valve connecting pipe 32). The calibration device includes a switch ball valve 33 in front of the meter clamp), a connecting pipe 56 in front of the meter clamp), a meter clamp 34), a front straight pipe section 35), an electromechanical conversion device 36 of the water meter to be inspected), a water meter to be inspected 37), a rear straight pipe section 38), a calibration device support frame 39), a manifold 40), a small-diameter back pressure switch ball valve 41), a back pressure switch ball valve 42 of the same diameter), a small-diameter back pressure pipeline 43), and a back pressure pipeline 44 of the same diameter. The pressurization system includes a pressurized water pump outlet pipeline 45), a switch ball valve 46 after the pressurized water pump), a pressurized water pump 47), a switch ball valve 48 in front of the pressurized water pump), and a pressurized water pump inlet pipeline 49); the pressurized water pump outlet pipe 45) is fixedly connected to the small-diameter back pressure pipeline 43) through a tee pipe. The exhaust system includes an exhaust water inlet pipeline 51), a switch ball valve 52 in front of the exhaust water pump), an exhaust water pump 53), a switch ball valve 54 after the exhaust water pump), and an exhaust water outlet pipeline 55).

The piston device as the main standard and the cylindrical piston 12), the piston cylinder front flange 17), the piston cylinder 18), the disc piston 23), and the piston cylinder rear flange 24 in the peripheral system together constitute a double standard type piston device. The cylindrical piston 12), the piston cylinder front flange 17), the piston cylinder 18), and the disc piston 23) together form a column-disc combination standard; the piston cylinder front flange 17) in the column-disc combination standard is fixedly installed at the front end of the piston cylinder 18), and the piston cylinder 18) and the piston cylinder front flange 17) are sealed by an O-ring; one end of the cylindrical piston 12) is fixedly connected to the floating joint 11), and the other end of the cylindrical piston 12) is fixedly connected to the disc piston 23), the disc piston 23) is located in the piston cylinder 18), and a Y-shaped sealing ring and a guide ring are installed between the disc piston 23) and the piston cylinder 18); the cylindrical piston 12) passes through the middle of the piston cylinder front flange 17), a part of which is located outside the piston cylinder 18), and the other part is located inside the piston cylinder 18), and a certain water-filled space is reserved between the part of the cylindrical piston 12) located inside the piston cylinder 18) and the piston cylinder 18), and a Y-shaped sealing ring is used to seal between the cylindrical piston 12) and the piston cylinder front flange 17), and the Y-shaped sealing ring is fixedly installed on the piston cylinder front flange 17); the front end, middle part and rear end of the cylindrical piston 12) are supported by the floating joint 11), the piston cylinder front flange 17), and the disc piston 23) respectively; the space between the piston cylinder front flange 17), the cylindrical piston 12) and the disc piston 23) in the piston cylinder 18) is a water-filled space. When working, the cylindrical piston 12) and the disc piston 23) move toward the piston cylinder front flange 17) (called the top of the piston cylinder 18)). The space between the piston cylinder front flange 17) and the cylindrical piston 23) in the piston cylinder 18) is a water-filled space. The space between the cylindrical piston 12) and the disc piston 23) is reduced. Since the Y-shaped sealing ring is used to seal between the cylindrical piston 12) and the front flange 17) of the piston cylinder, and between the disc piston 23) and the piston cylinder 18), the water in the water-filled space is compressed and discharged from the piston cylinder 18) through the front cylinder body water outlet pipe 19). The volume of water discharged from the piston cylinder 18) can be calculated based on the outer diameter of the cylindrical piston 12), the inner diameter of the piston cylinder 18) and the moving distance of the cylindrical piston 12) and the disc piston 23). The piston cylinder 18), the disc piston 23) and the rear flange 24) of the piston cylinder together form a disc standard. The piston cylinder rear flange 24) in the disc-shaped standard is fixedly installed at the rear end of the piston cylinder 18), and an O-ring is used to seal the piston cylinder 18) and the piston cylinder rear flange 24); the disc-shaped standard and the column-disc combined standard share a disc-shaped piston 23); the space between the piston cylinder rear flange 24) and the disc-shaped piston 23) in the piston cylinder 18) is a water-filled space. During operation, the disc-shaped piston 23) moves toward the piston cylinder rear flange 24) (called the bottom of the piston cylinder 18)), and the space between the piston cylinder rear flange 24) and the disc-shaped piston 23) in the piston cylinder 18) is reduced. Since the disc-shaped piston 23) and the piston cylinder 18) are sealed with a Y-ring, the water in the water-filled space is compressed and discharged from the piston cylinder 18) through the rear cylinder water outlet pipe 29), and the volume of water discharged from the piston cylinder 18) can be calculated based on the inner diameter of the piston cylinder 18) and the moving distance of the disc-shaped piston 23).

In addition, the pressurization system composed of the pressure water pump rear switch ball valve 46), the pressure water pump 47), the pressure water pump front switch ball valve 48), and the pressure water pump inlet pipe 49) and the small-diameter back pressure pipeline 43) and the rear straight pipe section 38) together constitute the small flow calibration back pressure system of the water meter calibration standard device.

The method of generating back pressure in the downstream straight pipe section 38) of the small flow calibration back pressure system of the water meter 37) under test includes the following steps and principles:

i) Control the rotation to a speed corresponding to the small flow point of the water meter 37) to be calibrated, and open the ball valve 48 in front of the pressure water pump) and start the pressure water pump 47).

ii) Under the action of the booster water pump 47), the water in the high-level water tank 50) passes through the booster water pump inlet pipe 49), the booster water pump front switch ball valve 48), the booster water pump 47), the booster water pump rear switch ball valve 46), and the booster water pump outlet pipe 45), and then enters the small-diameter back-pressure pipe 43), and finally flows into the high-level water tank 50) from the small-diameter back-pressure pipe 43).

iii) When the water supplied by the booster pump 47) flows into the high-level water tank 50) via the small-diameter back-pressure pipe 43), the water flow will quickly generate a back pressure in the small-diameter back-pressure pipe 43) that exceeds the minimum back pressure required for calibration of the water meter 37) under test due to the pressure loss in the pipe. The back pressure is transmitted to the water meter 37) under test through the rear straight pipe section 38).

iv) The start-up of the booster pump 47) is synchronized with the reverse acceleration control of the servo motor 1) when verifying the small flow point of the water meter 37) under inspection, and the flow stabilization time of the water flow supplied by the booster pump 47) and the constant speed time corresponding to the reverse acceleration of the servo motor 1) to the flow point of the water meter 37) under inspection are both short. The two can reach the flow balance point in a short time, that is, the small flow verification back pressure system can establish a constant and sufficient back pressure for the water meter 37) under inspection in a short time.

A method for exhausting the piston cylinder of a wide range ratio water meter calibration standard device comprises the following steps:

1) Close the front cylinder water inlet switch ball valve 13), the front cylinder water outlet switch ball valve 20), the rear cylinder water inlet switch ball valve 28) and the rear cylinder water outlet switch ball valve 30), and open the front cylinder manual exhaust ball valve 16) and the rear cylinder manual exhaust ball valve 25).

2) controls the servo motor 1) to rotate in the reverse direction to drive the reducer 2) to rotate in the same direction. The rotation of the servo motor 1) is reduced by the reducer 2) and drives the lead screw 6) to rotate in the reverse direction. The reverse rotation of the lead screw is converted into the reverse horizontal movement of the lead screw nut 10) through the cooperation of the lead screw 6) and the lead screw nut 10). The reverse horizontal movement of the lead screw nut 10) drives the slidable metal support 9) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the slidable metal support 9) drives the floating joint 11) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the floating joint 11) pulls the cylindrical piston 12) and the disc piston 23) to move in the reverse synchronous horizontal direction until the other end of the cylindrical piston 12) and the disc piston 23) reach the top of the piston cylinder 18).

3) Close the front cylinder manual exhaust ball valve 16), the front cylinder water outlet switch ball valve 20), the rear cylinder water inlet switch ball valve 28) and the rear cylinder water outlet switch ball valve 30), and open the front cylinder water inlet switch ball valve 13) and the rear cylinder manual exhaust ball valve 25).

4) Control the servo motor 1) to rotate forward and drive the reducer 2) to rotate in the same direction. The rotation of the servo motor 1) is decelerated by the reducer 2) and drives the lead screw 6) to rotate forward. The forward rotation of the lead screw is converted into the forward horizontal movement of the lead screw nut 10) through the cooperation of the lead screw 6) and the lead screw nut 10). The forward horizontal movement of the lead screw nut 10) drives the slidable metal support 9) to move forward synchronously horizontally. The forward synchronous horizontal movement of the slidable metal support 9) drives the floating joint 11) to move forward synchronously horizontally. The forward synchronous horizontal movement of the floating joint 11) pushes the cylindrical piston 12) and the disc piston 23) to move forward synchronously horizontally until the cylindrical piston 12 ) and the disc-shaped piston 23) reach the bottom of the piston cylinder 18); during the positive horizontal movement of the cylindrical piston 12) and the disc-shaped piston 23), the water in the high-level water tank 50) enters the space between the front flange 17 of the piston cylinder in the piston cylinder 18), the cylindrical piston 12) and the disc-shaped piston 23) through the front cylinder water inlet pipe 14) and the front cylinder water inlet switch ball valve 13) to form a water-filled space; during the positive horizontal movement of the cylindrical piston 12) and the disc-shaped piston 23), the air in the space between the rear flange 24 of the piston cylinder 18) and the disc-shaped piston 23) is discharged from the cylinder through the rear cylinder manual exhaust ball valve 25) and the rear cylinder exhaust pipe 26).

5) Close the rear cylinder manual exhaust ball valve 25), the rear cylinder water outlet switch ball valve 30), the front cylinder water inlet switch ball valve (13) and the front cylinder water outlet switch ball valve 20), and open the rear cylinder water inlet switch ball valve 28) and the front cylinder manual exhaust ball valve 16).

6) controls the servo motor 1) to rotate in the reverse direction to drive the reducer 2) to rotate in the same direction. The rotation of the servo motor 1) is decelerated by the reducer 2) to drive the lead screw 6) to rotate in the reverse direction. The reverse rotation of the lead screw is converted into the reverse horizontal movement of the lead screw nut 10) through the cooperation of the lead screw 6) and the lead screw nut 10). The reverse horizontal movement of the lead screw nut 10) drives the slidable metal support 9) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the slidable metal support 9) drives the floating joint 11) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the floating joint 11) pulls the cylindrical piston 12) and the disc piston 23) to move in the reverse synchronous horizontal direction until the cylindrical piston 12 ) and the disc-shaped piston 23) reach the top of the piston cylinder 18); during the reverse horizontal movement of the columnar piston 12) and the disc-shaped piston 23), the water in the high-level water tank 50) enters the water-filled space between the rear flange 24 of the piston cylinder 18) and the disc-shaped piston 23) through the rear cylinder water inlet pipe 27) and the rear cylinder water inlet switch ball valve 28); during the reverse synchronous horizontal movement of the columnar piston 12) and the disc-shaped piston 23), the air in the space between the front flange 17 of the piston cylinder 18), the columnar piston 12) and the disc-shaped piston 23) is discharged out of the cylinder through the front cylinder manual exhaust ball valve 16) and the front cylinder exhaust pipe 15).

7) Close the front cylinder manual exhaust ball valve 16), the front cylinder water outlet switch ball valve 20), the rear cylinder manual exhaust ball valve 25) and the rear cylinder water inlet switch ball valve 28), and open the front cylinder water inlet switch ball valve 13) and the rear cylinder water outlet switch ball valve 30).

8) controls the servo motor 1) to rotate forward and drives the reducer 2) to rotate in the same direction. The rotation of the servo motor 1) is decelerated by the reducer 2) and drives the lead screw 6) to rotate forward. The forward rotation of the lead screw is converted into the forward horizontal movement of the lead screw nut 10) through the cooperation of the lead screw 6) and the lead screw nut 10). The forward horizontal movement of the lead screw nut 10) drives the slidable metal support 9) to move forward synchronously horizontally. The forward synchronous horizontal movement of the slidable metal support 9) drives the floating joint 11) to move forward synchronously horizontally. The forward synchronous horizontal movement of the floating joint 11) pushes the cylindrical piston 12) and the disc piston 23) to move forward synchronously horizontally until the other end of the cylindrical piston 12) and the disc piston 23) reach the bottom of the piston cylinder 18); after the cylindrical piston 12) and the disc piston During the positive horizontal movement of the piston cylinder 18), the water in the high-level water (50) enters the space between the piston cylinder front flange 17), the cylindrical piston 12) and the disc piston 23) through the front cylinder water inlet pipe 14) and the front cylinder water inlet switch ball valve 13) to form a water-filled space; during the positive horizontal movement of the cylindrical piston 12) and the disc piston 23), the water in the water-filled space between the piston cylinder rear flange 24) and the disc piston 23) is discharged outward through the rear cylinder water outlet switch ball valve 30) and the rear cylinder water outlet pipe 29), and at the same time, the air in the rear cylinder water outlet switch ball valve 30) and the rear cylinder water outlet pipe 29) flows out together with the discharged water, and finally the air in the rear cylinder water outlet switch ball valve 30) and the rear cylinder water outlet pipe 29) is completely discharged.

9) Close the front cylinder manual exhaust ball valve 16), the front cylinder water inlet switch ball valve 13), the rear cylinder water outlet switch ball valve 30) and the rear cylinder manual exhaust ball valve 25), and open the front cylinder water outlet switch ball valve 20), the front and rear cylinder water outlet pipe isolation ball valves 31) and the rear cylinder water inlet switch ball valve 28).

10) controls the servo motor 1) to rotate in the reverse direction and drives the reducer 2) to rotate in the same direction. The rotation of the servo motor 1) is reduced by the reducer 2) and drives the lead screw 6) to rotate in the reverse direction. The reverse rotation of the lead screw is converted into the reverse horizontal movement of the lead screw nut 10) through the cooperation of the lead screw 6) and the lead screw nut 10). The reverse horizontal movement of the lead screw nut 10) drives the slidable metal support 9) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the slidable metal support 9) drives the floating joint 11) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the floating joint 11) pulls the cylindrical piston 12) and the disc piston 23) to move in the reverse synchronous horizontal direction until the other end of the cylindrical piston 12) and the disc piston 23) reach the top of the piston cylinder 18); when the cylindrical piston 12) and the disc piston 23) move in the reverse direction, During the horizontal movement, the water in the high-level water tank 50) enters the water-filled space between the rear flange 24 of the piston cylinder 18) and the disc piston 23) through the rear cylinder water inlet pipe 27) and the rear cylinder water inlet switch ball valve 28); during the reverse synchronous horizontal movement of the cylindrical piston 12) and the disc piston 23) , the water in the space between the piston cylinder front flange 17) , the cylindrical piston 12) and the disc piston 23) in the piston cylinder 18) is discharged outward through the front cylinder water outlet switch ball valve 20) and the front cylinder water outlet pipe 19) , and at the same time, the air in the front cylinder water outlet switch ball valve 20) and the front cylinder water outlet pipe 19) flows out together with the discharged water, and finally the air in the front cylinder water outlet switch ball valve 20) , the front cylinder water outlet pipe 19) and the front and rear cylinder water outlet pipe isolation ball valve (31) is completely discharged.

11) Repeat steps 3), 4), 5) and 6) to remove the air in the space between the rear flange 24 of the piston cylinder 18) and the disc piston 23) and the air in the space between the front flange 17 of the piston cylinder 18), the columnar piston 12) and the disc piston 23) in the piston cylinder 18).

The method for calibrating the flow rate of a water meter using a wide range ratio water meter calibration standard device comprises the following steps:

A. Calibration of large flow points

a) Install the water meter 37) to be tested between the front straight pipe section 35) and the rear straight pipe section 38).

b) Execute step 9), control the servo motor 1) to rotate in the reverse direction to drive the reducer 2) to rotate in the same direction, the rotation of the servo motor (1) is reduced by the reducer 2) to drive the lead screw 6) to rotate in the reverse direction, the reverse rotation of the lead screw is converted into the reverse horizontal movement of the lead screw nut 10) through the cooperation between the lead screw 6) and the lead screw nut 10), the reverse horizontal movement of the lead screw nut 10) drives the slidable metal support 9) to move in the reverse synchronous horizontal direction, the reverse synchronous horizontal movement of the slidable metal support 9) drives the floating joint 11) to move in the reverse synchronous horizontal direction, the reverse synchronous horizontal movement of the floating joint 11) pulls the columnar piston 12) and the disc piston 23) to move in the reverse synchronous horizontal direction, until the other end of the columnar piston 12) and the disc piston 23) reach the top of the piston cylinder 18).

c) Close the isolation ball valves 31) of the front and rear cylinder water outlet pipes and the switch ball valve 30) of the rear cylinder water outlet; open the switch ball valve 33 in front of the meter clamp), the small-diameter back pressure switch ball valve 41), the same-diameter back pressure switch ball valve 42), the switch ball valve 52) in front of the exhaust water pump and the switch ball valve 54) in the rear of the exhaust water pump, start the exhaust water pump 53) to remove the air in the rear cylinder water outlet pipe 29), the switch ball valve 33 in front of the meter clamp), the connecting pipe 56 in front of the meter clamp), the meter clamp 34), the front straight pipe section 35), the water meter to be inspected 37), the rear straight pipe section 38), the manifold 40), the small-diameter back pressure switch ball valve 41), the same-diameter back pressure switch ball valve 42), the small-diameter back pressure pipe 43), the same-diameter back pressure pipe 44), the exhaust water inlet pipe 51), the switch ball valve 52 in front of the exhaust water pump), the exhaust water pump 53), and the exhaust water outlet pipe 55).

d) Close the front cylinder manual exhaust ball valve 16), the front cylinder water outlet switch ball valve 20), the front and rear cylinder water outlet pipe isolation ball valve 31), the rear cylinder manual exhaust ball valve 25), the rear cylinder water inlet switch ball valve 28), the exhaust water pump rear switch ball valve 54), and the small-diameter back pressure switch ball valve 41); open the front cylinder water inlet switch ball valve 13), the rear cylinder water outlet switch ball valve 30), the meter clamp front switch ball valve 33), and the same-diameter back pressure switch ball valve 42).

e) Control the servo motor 1) to accelerate forward to a speed corresponding to the required calibration flow and then keep rotating at a constant speed. At the same time, the forward rotation of the servo motor 1) is decelerated by a certain reduction ratio of the reducer 2) to drive the lead screw 6) to rotate forward, and the rotation of the lead screw 3) is converted into horizontal movement of the column piston 12) and the disc piston 23) through the cooperation between the lead screw 3) and the lead screw nut 10), the slidable metal support 9), the floating joint 11), the column piston 12) and the disc piston 23). The horizontal movement of the column piston 12) and the disc piston 23) on the one hand sucks the water in the high-level water tank 50) through the front cylinder water inlet pipe 14) and the front cylinder water inlet switch ball valve 13) into the space between the piston cylinder front flange 17), the column piston 12) and the disc piston 23) in the piston cylinder 18). On the other hand, the water in the water-filled space between the rear flange 24 of the piston cylinder and the disc piston 23) is discharged outward through the rear cylinder water outlet switch ball valve 30) and the rear cylinder water outlet pipe 29) at the required calibration flow rate under the push of the disc piston 23), and enters the high-level water tank 50) after passing through the front switch ball valve 33 of the meter clamp), the front connecting pipe (56) of the meter clamp, the meter clamp 34), the front straight pipe section 35), the water meter to be inspected 37), the rear straight pipe section 38), the manifold 40), the same-diameter back-pressure switch ball valve 42), and the same-diameter back-pressure pipe 44); after the cylindrical piston 12) and the disc piston 23) are correspondingly changed from accelerated horizontal movement to uniform horizontal movement, the time frequency recorder starts to accumulate the frequency of the driving servo motor 1) and records the frequency accumulation start time t ₁ ; after the cylindrical piston 12) and the disc piston 23) correspondingly change from accelerated horizontal movement to uniform horizontal movement, the time-frequency recorder starts to accumulate the frequency signal of the output of the inspected water meter 37), and records the frequency accumulation start time _t'1 ; when the accumulation of the frequency signal of the output of the inspected water meter 37) by the time-frequency recorder reaches the minimum number of frequency signals, the time-frequency recorder stops accumulating the frequency signal of the output of the inspected water meter 37), and records the accumulation stop time _t'2 and the accumulated number N' of frequency signals; after the time-frequency recorder stops accumulating the frequency signal of the output of the inspected water meter 37), the time-frequency recorder then stops accumulating the frequency signal of the output of the inspected water meter 37), and records the accumulation stop time _t2 and the accumulated number N of frequency signals.

f) According to the cumulative number N' of the frequency signals of the inspected water meter 37) recorded by the time frequency recorder and the corresponding cumulative start time _t'1 and end time _t'2 , the average flow of the inspected water meter 37) during the frequency signal accumulation time period is calculated according to formula (1):

Q＝(P×N')/( _t'2 - _t'1 ) (1)

Wherein, Q is the average flow rate in the time period during which the frequency signals output by the inspected water meter 37) are accumulated; and P is the cumulative amount of water represented by each frequency signal when water flows through the inspected water meter 37).

g) According to the cumulative number N of the frequency signals of the servo motor (1) recorded by the time frequency recorder and the corresponding cumulative start time _t1 and end time _t2 , the average flow rate of the water meter calibration standard device within the frequency signal accumulation time period is calculated according to formula (2):

q＝πD ² ipωN/[4(t ₂ -t ₁ )] (2)

Wherein, q is the average flow rate of the water meter calibration standard device within the frequency signal accumulation time period; π is the pi; D is the inner diameter of the piston cylinder 18); i is the speed ratio of the reducer 2); p is the lead of the screw 6); ω is the angle of rotation of the servo motor 1) when the servo motor 1) receives each frequency signal.

h) According to formula (3), the indication error of the inspected water meter 37) at the inspected flow point is calculated as follows:

E＝(Q-q)/q×100％ (3)

Where, E is the indication error of the inspected flow point of the inspected water meter 37).

i) judging whether the servo motor 1) can continue to rotate in the same direction according to the next calibration flow point of the water meter 37) to be inspected, its calibration time and the distance that the disc-shaped piston 23) has moved horizontally: if it can continue to rotate in the same direction, repeating steps e) to h) to complete the calibration of the next flow point; if it can no longer continue to rotate in the same direction, first executing step b), and then executing steps d) to h) to complete the calibration of the next flow point;

j) Repeat step i) to complete the calibration of other large flow points of the water meter 37).

B. Calibration of small flow points

a') judging whether the servo motor 1) can make reverse rotation according to the small flow verification flow point of the water meter 37) under inspection, its verification time and the distance that the disc-shaped piston 23) has moved horizontally: if it can make reverse rotation, executing steps c') to g'); if it cannot make reverse rotation, executing step b), and then executing steps c') to g');

b') Repeat step a') to complete the calibration of other small flow points of the water meter 37) under inspection.

c') close the front cylinder manual exhaust ball valve 16), the front cylinder water inlet switch ball valve 13), the rear cylinder manual exhaust ball valve 25), the rear cylinder water outlet switch ball valve 30), the same diameter back pressure switch ball valve 42), and the exhaust water pump rear switch ball valve 54); open the front cylinder water outlet switch ball valve 20), the rear cylinder water inlet switch ball valve 28), the front and rear cylinder water outlet pipe isolation ball valve 31), the small-diameter back pressure switch ball valve 41), the pressure water pump rear switch ball valve 46), and the pressure water pump front switch ball valve 48);

d') controls the servo motor 1) to accelerate in the reverse direction to a speed corresponding to the required calibration flow rate and then keeps rotating at a constant speed. Meanwhile, the reverse rotation of the servo motor 1) is decelerated by a certain reduction ratio of the reducer 2) and drives the lead screw 6) to rotate in the reverse direction. The rotation of the lead screw 3) is converted into horizontal movement of the column piston 12) and the disc piston 23) through the cooperation between the lead screw 3) and the lead screw nut 10), the slidable metal support 9), the floating joint 11), the column piston 12) and the disc piston 23). The horizontal movement of the column piston 12) and the disc piston 23) on the one hand pushes the water in the high-level water tank 50) into the rear cylinder body. The water pipe 27) and the rear cylinder water inlet switch ball valve 28) are sucked into the water-filled space between the rear flange 24 of the piston cylinder 18) and the disc piston 23). On the other hand, the water in the water-filled space between the front flange 17 of the piston cylinder 18), the column piston 12) and the disc piston 23) is pushed by the disc piston 23) to be discharged outward at the required calibration flow rate through the front cylinder water outlet switch ball valve 20), the front cylinder water outlet pipe 19), and the front and rear cylinder water outlet pipe isolation ball valve 31), and passes through the meter clamp front switch ball valve 33), the meter clamp front connecting pipe 56), the meter clamp 34), and the front straight pipe section 35 ), the inspected water meter 37), the rear straight pipe section 38), the manifold 40), the small-diameter back-pressure switch ball valve 41), the small-diameter back-pressure pipe 43), and then enter the high-level water tank 50); while controlling the servo motor 1) to accelerate the rotation in the reverse direction, start the pressure water pump 47), under the action of the pressure water pump 47), the water in the high-level water tank 50) passes through the pressure water pump inlet pipe 49), the pressure water pump front switch ball valve 48), the pressure water pump 47), the pressure water pump rear switch ball valve 46), the pressure water pump outlet pipe 45), and then enters the small-diameter back-pressure pipe 43), and finally flows into the high-level water tank 50) from the small-diameter back-pressure pipe 43), the pressure When the water flow supplied by the water pressure pump 47) flows into the high-level water tank 50) via the small-diameter back pressure pipe 43), the water flow in the small-diameter back pressure pipe 43) will quickly generate a back pressure exceeding the minimum back pressure required for the calibration of the water meter 37) under test, and the back pressure is transmitted to the water meter 37) under test through the rear straight pipe section 38), and finally quickly generates a constant back pressure exceeding the minimum back pressure required for the water meter 37) under test in the rear straight pipe section 38); after a constant back pressure exceeding the minimum back pressure required for the water meter 37) under test is generated in the rear straight pipe section 38), the time frequency recorder starts to accumulate the frequency of the drive servo motor 1) to rotate, and records the frequency accumulation start time t ₁ ; after the time-frequency recorder starts to accumulate the frequency of the driving servo motor 1), the time-frequency recorder starts to accumulate the frequency signal of the output of the inspected water meter 37), and records the frequency accumulation start time _t'1 ; when the accumulation of the frequency signal of the output of the inspected water meter 37) by the time-frequency recorder reaches the minimum number of frequency signals, the time-frequency recorder stops accumulating the frequency signal of the output of the inspected water meter 37), and records the accumulation stop time _t'2 and the accumulated number N' of frequency signals; after the time-frequency recorder stops accumulating the frequency signal of the output of the inspected water meter 37), the time-frequency recorder then stops accumulating the frequency signal of the output of the inspected water meter 37), and records the accumulation stop time _t2 and the accumulated number N of frequency signals;

e') executing step f);

f') According to the cumulative number N of the frequency signals of the servo motor 1) recorded by the time frequency recorder and the corresponding cumulative start time _t1 and end time _t2 , the average flow rate of the water meter calibration standard device within the frequency signal accumulation time period is calculated according to formula (4):

q＝πipωN(D ² -D ₁ ² )/[4(t ₂ -t ₁ )] (4)

Wherein, q is the average flow rate of the water meter calibration standard device within the frequency signal accumulation time period; π is the pi; i is the speed ratio of the reducer 2); p is the lead of the screw 6); ω is the angle of rotation of the servo motor 1) when the servo motor 1) receives each frequency signal; D is the inner diameter of the piston cylinder 18); _D1 is the outer diameter of the cylindrical piston 12).

g') execute step h).

Claims (3)

1. A method for generating back pressure in a rear straight pipe section (38) downstream of a water meter (37) to be inspected by a small flow rate verification back pressure system, using a wide range ratio water meter verification standard device, the device comprising a piston device as a main standard and a peripheral system, a verification device, a pressurizing system, a high-level water tank (50) and an exhaust system; The piston device and peripheral system as the main standard include a servo motor (1), a reducer (2), a reducer metal support (3), a coupling (4), a screw front metal support (5), a screw (6), a linear guide (7), a piston metal bracket (8), a slidable metal support (9), a screw nut (10), a floating joint (11), a cylindrical piston (12), a front cylinder water inlet switch ball valve (13), a front cylinder water inlet pipe (14), a front cylinder exhaust pipe (15), a front cylinder manual exhaust ball valve (16), a piston cylinder front flange (17), and a movable A plug cylinder (18), a front cylinder water outlet pipe (19), a front cylinder water outlet switch ball valve (20), a screw rear metal support (21), a piston metal support (22), a disc-shaped piston (23), a piston cylinder rear flange (24), a rear cylinder manual exhaust ball valve (25), a rear cylinder exhaust pipe (26), a rear cylinder water inlet pipe (27), a rear cylinder water inlet switch ball valve (28), a rear cylinder water outlet pipe (29), a rear cylinder water outlet switch ball valve (30), a front and rear cylinder water outlet pipe isolation ball valve (31), and a front and rear cylinder water outlet pipe isolation ball valve connecting pipe (32); The calibration device comprises a front switch ball valve (33) of the meter clamp, a front connecting pipe (56) of the meter clamp, a meter clamp (34), a front straight pipe section (35), an electromechanical conversion device (36) of the water meter to be tested, a water meter to be tested (37), a rear straight pipe section (38), a calibration device support frame (39), a manifold (40), a small-diameter back-pressure switch ball valve (41), a back-pressure switch ball valve (42) of the same diameter, a small-diameter back-pressure pipe (43), and a back-pressure pipe (44) of the same diameter; The pressurizing system comprises a pressurizing water pump outlet pipe (45), a pressure water pump rear switch ball valve (46), a pressurizing water pump (47), a pressure water pump front switch ball valve (48), and a pressurizing water pump inlet pipe (49); the pressurizing water pump outlet pipe (45) is fixedly connected to the small-diameter back pressure pipe (43) through a tee pipe; The exhaust system comprises an exhaust water inlet pipe (51), a switch ball valve (52) before the exhaust water pump, an exhaust water pump (53), a switch ball valve (54) after the exhaust water pump, and an exhaust water outlet pipe (55); The cylindrical piston (12), the piston cylinder front flange (17), the piston cylinder (18), the disc piston (23), and the piston cylinder rear flange (24) together constitute a double standard piston device; the cylindrical piston (12), the piston cylinder front flange (17), the piston cylinder (18), and the disc piston (23) together constitute a column-disc combination standard; the piston cylinder front flange (17) in the column-disc combination standard is fixedly installed at the front end of the piston cylinder (18), and an O-type sealing ring is used to seal between the piston cylinder (18) and the piston cylinder front flange (17); one end of the cylindrical piston (12) is fixedly connected to the floating joint (11), and the other end of the cylindrical piston (12) is fixedly connected to the disc piston (23), the disc piston (23) is located in the piston cylinder (18), and a Y-type sealing ring and a guide are installed between the disc piston (23) and the piston cylinder (18). The cylindrical piston (12) passes through the middle of the piston cylinder front flange (17), a part of which is located outside the piston cylinder (18) and the other part is located inside the piston cylinder (18). A certain water-filled space is reserved between the part of the cylindrical piston (12) located inside the piston cylinder (18) and the piston cylinder (18). A Y-shaped sealing ring is used to seal between the cylindrical piston (12) and the piston cylinder front flange (17). The Y-shaped sealing ring is fixedly mounted on the piston cylinder front flange (17). The front end, middle part and rear end of the cylindrical piston (12) are supported by the floating joint (11), the piston cylinder front flange (17) and the disc piston (23) respectively. The space in the piston cylinder (18) between the piston cylinder front flange (17), the cylindrical piston (12) and the disc piston (23) is a water-filled space. When working, the cylindrical piston (12) and the disc piston (23) push toward the piston cylinder front flange. When the piston cylinder (18) moves in the direction of rotation (17), the space between the front flange (17) of the piston cylinder, the columnar piston (12) and the disc-shaped piston (23) in the piston cylinder (18) is reduced. Since the columnar piston (12) and the front flange (17) of the piston cylinder, and the disc-shaped piston (23) and the piston cylinder (18) are sealed by Y-shaped sealing rings, the water in the water-filled space is compressed and discharged from the piston cylinder (18) through the front cylinder body water outlet pipe (19). The volume of water discharged from the piston cylinder (18) can be calculated based on the outer diameter of the columnar piston (12), the inner diameter of the piston cylinder (18) and the moving distance of the columnar piston (12) and the disc-shaped piston (23); the piston cylinder (18), the disc-shaped piston (23) and the rear flange (24) of the piston cylinder together form a disc-shaped standard device; the rear flange (24) of the piston cylinder in the disc-shaped standard device is fixedly mounted on the piston cylinder (18) ), an O-ring is used to seal the rear end of the piston cylinder (18) and the rear flange (24) of the piston cylinder; the disc-shaped standard and the column-disk combined standard share the disc-shaped piston (23); the space between the rear flange (24) of the piston cylinder and the disc-shaped piston (23) in the piston cylinder (18) is a water-filled space. During operation, the disc-shaped piston (23) moves toward the rear flange (24) of the piston cylinder, and the space between the rear flange (24) of the piston cylinder and the disc-shaped piston (23) in the piston cylinder (18) is reduced. Since the disc-shaped piston (23) and the piston cylinder (18) are sealed by a Y-ring, the water in the water-filled space is compressed and discharged from the piston cylinder (18) through the rear cylinder body water outlet pipe (29). The volume of water discharged from the piston cylinder (18) can be calculated based on the inner diameter of the piston cylinder (18) and the moving distance of the disc-shaped piston (23); The pressurized system composed of the pressure water pump rear switch ball valve (46), the pressure water pump (47), the pressure water pump front switch ball valve (48), and the pressure water pump inlet pipe (49) together with the small-diameter back pressure pipeline (43) and the rear straight pipe section (38) constitutes a small flow calibration back pressure system of the water meter calibration standard device; It is characterized by comprising the following steps: i) controlling the servo motor (1) to rotate to a speed corresponding to the small flow point of the water meter (37) to be calibrated, while opening the switch ball valve (48) in front of the pressure water pump and starting the pressure water pump (47); ii) Under the action of the booster water pump (47), the water in the high-level water tank (50) passes through the booster water pump water inlet pipe (49), the booster water pump front switch ball valve (48), the booster water pump (47), the booster water pump rear switch ball valve (46), the booster water pump outlet pipe (45), and then enters the small-diameter back-pressure pipe (43), and finally flows into the high-level water tank (50) from the small-diameter back-pressure pipe (43); iii) When the water supplied by the booster pump (47) flows into the high-level water tank (50) via the small-diameter back-pressure pipe (43), the water flow will quickly generate a back pressure exceeding the minimum back pressure required for calibrating the water meter (37) to be inspected in the small-diameter back-pressure pipe (43) due to the pressure loss of the pipe. The back pressure is transmitted to the water meter (37) to be inspected through the rear straight pipe section (38); iv) The start-up of the booster pump (47) is synchronized with the reverse acceleration control of the servo motor (1) when verifying the small flow point of the water meter (37) under test, and the flow stabilization time of the water flow supplied by the booster pump (47) and the reverse acceleration time of the servo motor (1) to the constant speed corresponding to the flow point of the water meter (37) under test are both short. The two can reach the flow balance point in a short time, that is, the small flow verification back pressure system can establish a constant and sufficient back pressure for the water meter (37) under test in a short time. 2. A method for exhausting the piston cylinder of a wide range ratio water meter calibration standard device, the wide range ratio water meter calibration standard device comprising a piston device as a main standard and a peripheral system, a calibration device, a pressurizing system, a high-level water tank (50) and an exhaust system; The piston device and peripheral system as the main standard include a servo motor (1), a reducer (2), a reducer metal support (3), a coupling (4), a screw front metal support (5), a screw (6), a linear guide (7), a piston metal bracket (8), a slidable metal support (9), a screw nut (10), a floating joint (11), a cylindrical piston (12), a front cylinder water inlet switch ball valve (13), a front cylinder water inlet pipe (14), a front cylinder exhaust pipe (15), a front cylinder manual exhaust ball valve (16), a piston cylinder front flange (17), and a movable A plug cylinder (18), a front cylinder water outlet pipe (19), a front cylinder water outlet switch ball valve (20), a screw rear metal support (21), a piston metal support (22), a disc-shaped piston (23), a piston cylinder rear flange (24), a rear cylinder manual exhaust ball valve (25), a rear cylinder exhaust pipe (26), a rear cylinder water inlet pipe (27), a rear cylinder water inlet switch ball valve (28), a rear cylinder water outlet pipe (29), a rear cylinder water outlet switch ball valve (30), a front and rear cylinder water outlet pipe isolation ball valve (31), and a front and rear cylinder water outlet pipe isolation ball valve connecting pipe (32); The calibration device comprises a switch ball valve (33) in front of the meter clamp, a connecting pipe (56) in front of the meter clamp, a meter clamp (34), a front straight pipe section (35), an electromechanical conversion device (36) of the water meter to be inspected, a water meter to be inspected (37), a rear straight pipe section (38), a calibration device support frame (39), a manifold (40), a small-diameter back-pressure switch ball valve (41), a back-pressure switch ball valve (42) of the same diameter, a small-diameter back-pressure pipe (43), and a back-pressure pipe (44) of the same diameter; The pressurizing system comprises a pressurizing water pump outlet pipe (45), a pressure water pump rear switch ball valve (46), a pressurizing water pump (47), a pressure water pump front switch ball valve (48), and a pressurizing water pump inlet pipe (49); the pressurizing water pump outlet pipe (45) is fixedly connected to the small-diameter back pressure pipe (43) through a tee pipe; The exhaust system comprises an exhaust water inlet pipe (51), a switch ball valve (52) before the exhaust water pump, an exhaust water pump (53), a switch ball valve (54) after the exhaust water pump, and an exhaust water outlet pipe (55); The cylindrical piston (12), the piston cylinder front flange (17), the piston cylinder (18), the disc-shaped piston (23), and the piston cylinder rear flange (24) together constitute a double standard piston device; the cylindrical piston (12), the piston cylinder front flange (17), the piston cylinder (18), and the disc-shaped piston (23) together constitute a column-disc combination standard; the piston cylinder front flange (17) in the column-disc combination standard is fixedly installed at the front end of the piston cylinder (18), and an O-type sealing ring is used to seal between the piston cylinder (18) and the piston cylinder front flange (17); one end of the cylindrical piston (12) is fixedly connected to the floating joint (11), and the other end of the cylindrical piston (12) is fixedly connected to the disc-shaped piston (23), the disc-shaped piston (23) is located in the piston cylinder (18), and a Y-shaped sealing ring and a guide are installed between the disc-shaped piston (23) and the piston cylinder (18). The cylindrical piston (12) passes through the middle of the piston cylinder front flange (17), a part of which is located outside the piston cylinder (18) and the other part is located inside the piston cylinder (18). A certain water-filled space is reserved between the part of the cylindrical piston (12) located inside the piston cylinder (18) and the piston cylinder (18). A Y-shaped sealing ring is used to seal between the cylindrical piston (12) and the piston cylinder front flange (17). The Y-shaped sealing ring is fixedly mounted on the piston cylinder front flange (17). The front end, middle part and rear end of the cylindrical piston (12) are supported by the floating joint (11), the piston cylinder front flange (17) and the disc piston (23) respectively. The space in the piston cylinder (18) between the piston cylinder front flange (17), the cylindrical piston (12) and the disc piston (23) is a water-filled space. When working, the cylindrical piston (12) and the disc piston (23) push toward the piston cylinder front flange. When the piston cylinder (18) moves in the direction of rotation (17), the space between the front flange (17) of the piston cylinder, the columnar piston (12) and the disc-shaped piston (23) in the piston cylinder (18) is reduced. Since the columnar piston (12) and the front flange (17) of the piston cylinder, and the disc-shaped piston (23) and the piston cylinder (18) are sealed by Y-shaped sealing rings, the water in the water-filled space is compressed and discharged from the piston cylinder (18) through the front cylinder body water outlet pipe (19). The volume of water discharged from the piston cylinder (18) can be calculated based on the outer diameter of the columnar piston (12), the inner diameter of the piston cylinder (18) and the moving distance of the columnar piston (12) and the disc-shaped piston (23); the piston cylinder (18), the disc-shaped piston (23) and the rear flange (24) of the piston cylinder together form a disc-shaped standard device; the rear flange (24) of the piston cylinder in the disc-shaped standard device is fixedly mounted on the piston cylinder (18) ), an O-ring is used to seal the rear end of the piston cylinder (18) and the rear flange (24) of the piston cylinder; the disc-shaped standard and the column-disk combined standard share the disc-shaped piston (23); the space between the rear flange (24) of the piston cylinder and the disc-shaped piston (23) in the piston cylinder (18) is a water-filled space. During operation, the disc-shaped piston (23) moves toward the rear flange (24) of the piston cylinder, and the space between the rear flange (24) of the piston cylinder and the disc-shaped piston (23) in the piston cylinder (18) is reduced. Since the disc-shaped piston (23) and the piston cylinder (18) are sealed by a Y-ring, the water in the water-filled space is compressed and discharged from the piston cylinder (18) through the rear cylinder body water outlet pipe (29). The volume of water discharged from the piston cylinder (18) can be calculated based on the inner diameter of the piston cylinder (18) and the moving distance of the disc-shaped piston (23); It is characterized by comprising the following steps: 1) closing the front cylinder water inlet switch ball valve (13), the front cylinder water outlet switch ball valve (20), the rear cylinder water inlet switch ball valve (28) and the rear cylinder water outlet switch ball valve (30), and opening the front cylinder manual exhaust ball valve (16) and the rear cylinder manual exhaust ball valve (25); 2) controlling the servo motor (1) to rotate in the reverse direction to drive the reducer (2) to rotate in the same direction; the rotation of the servo motor (1) is decelerated by the reducer (2) to drive the lead screw (6) to rotate in the reverse direction; the reverse rotation of the lead screw is converted into reverse horizontal movement of the lead screw nut (10) through the cooperation between the lead screw (6) and the lead screw nut (10); the reverse horizontal movement of the lead screw nut (10) drives the slidable metal support (9) to move in the reverse synchronous horizontal direction; the reverse synchronous horizontal movement of the slidable metal support (9) drives the floating joint (11) to move in the reverse synchronous horizontal direction; the reverse synchronous horizontal movement of the floating joint (11) pulls the columnar piston (12) and the disc piston (23) to move in the reverse synchronous horizontal direction until the other end of the columnar piston (12) and the disc piston (23) reach the top of the piston cylinder (18); 3) closing the front cylinder manual exhaust ball valve (16), the front cylinder water outlet switch ball valve (20), the rear cylinder water inlet switch ball valve (28) and the rear cylinder water outlet switch ball valve (30), and opening the front cylinder water inlet switch ball valve (13) and the rear cylinder manual exhaust ball valve (25); 4) Controlling the servo motor (1) to rotate in the forward direction to drive the reducer (2) to rotate in the same direction. The rotation of the servo motor (1) is decelerated by the reducer (2) to drive the lead screw (6) to rotate in the forward direction. The forward rotation of the lead screw is converted into the forward horizontal movement of the lead screw nut (10) through the cooperation between the lead screw (6) and the lead screw nut (10). The forward horizontal movement of the lead screw nut (10) drives the slidable metal support (9) to move in the forward synchronous horizontal direction. The forward synchronous horizontal movement of the slidable metal support (9) drives the floating joint (11) to move in the forward synchronous horizontal direction. The forward synchronous horizontal movement of the floating joint (11) drives the cylindrical piston (12) and the disc piston (23) to move in the forward synchronous horizontal direction until the cylindrical piston (12) moves in the forward synchronous horizontal direction. The other end of the cylindrical piston (12) and the disc-shaped piston (23) reach the bottom of the piston cylinder (18); during the positive horizontal movement of the cylindrical piston (12) and the disc-shaped piston (23), the water in the high-level water tank (50) enters the space between the front flange (17) of the piston cylinder, the cylindrical piston (12) and the disc-shaped piston (23) in the piston cylinder (18) through the front cylinder water inlet pipe (14) and the front cylinder water inlet switch ball valve (13) to form a water-filled space; during the positive horizontal movement of the cylindrical piston (12) and the disc-shaped piston (23), the air in the space between the rear flange (24) of the piston cylinder (18) and the disc-shaped piston (23) is discharged from the cylinder through the rear cylinder manual exhaust ball valve (25) and the rear cylinder exhaust pipe (26); 5) closing the rear cylinder manual exhaust ball valve (25), the rear cylinder water outlet switch ball valve (30), the front cylinder water inlet switch ball valve (13) and the front cylinder water outlet switch ball valve (20), and opening the rear cylinder water inlet switch ball valve (28) and the front cylinder manual exhaust ball valve (16); 6) Controlling the servo motor (1) to rotate in the reverse direction to drive the reducer (2) to rotate in the same direction. The rotation of the servo motor (1) is decelerated by the reducer (2) to drive the lead screw (6) to rotate in the reverse direction. The reverse rotation of the lead screw is converted into reverse horizontal movement of the lead screw nut (10) through the cooperation between the lead screw (6) and the lead screw nut (10). The reverse horizontal movement of the lead screw nut (10) drives the slidable metal support (9) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the slidable metal support (9) drives the floating joint (11) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the floating joint (11) pulls the cylindrical piston (12) and the disc piston (23) to move in the reverse synchronous horizontal direction until the cylindrical piston (12) The other end of the cylinder (12) and the disc-shaped piston (23) reach the top of the piston cylinder (18); during the reverse horizontal movement of the columnar piston (12) and the disc-shaped piston (23), the water in the high-level water tank (50) enters the water-filled space between the rear flange (24) of the piston cylinder (18) and the disc-shaped piston (23) through the rear cylinder water inlet pipe (27) and the rear cylinder water inlet switch ball valve (28); during the reverse synchronous horizontal movement of the columnar piston (12) and the disc-shaped piston (23), the air in the space between the front flange (17) of the piston cylinder, the columnar piston (12) and the disc-shaped piston (23) in the piston cylinder (18) is discharged outside the cylinder through the front cylinder manual exhaust ball valve (16) and the front cylinder exhaust pipe (15); 7) Close the front cylinder manual exhaust ball valve (16), the front cylinder water outlet switch ball valve (20), the rear cylinder manual exhaust ball valve (25) and the rear cylinder water inlet switch ball valve (28), and open the front cylinder water inlet switch ball valve (13) and the rear cylinder water outlet switch ball valve (30); 8) Controlling the servo motor (1) to rotate in the forward direction to drive the reducer (2) to rotate in the same direction. The rotation of the servo motor (1) is decelerated by the reducer (2) to drive the lead screw (6) to rotate in the forward direction. The forward rotation of the lead screw is converted into the forward horizontal movement of the lead screw nut (10) through the cooperation between the lead screw (6) and the lead screw nut (10). The forward horizontal movement of the lead screw nut (10) drives the slidable metal support (9) to move in the forward synchronous horizontal direction. The forward synchronous horizontal movement of the slidable metal support (9) drives the floating joint (11) to move in the forward synchronous horizontal direction. The forward synchronous horizontal movement of the floating joint (11) drives the columnar piston (12) and the disc piston (23) to move in the forward synchronous horizontal direction until the other end of the columnar piston (12) and the disc piston (23) reach the bottom of the piston cylinder (18); after the columnar piston (12) and the disc piston (23) During the positive horizontal movement, the water in the high-level water tank (50) enters the space between the front flange (17) of the piston cylinder, the columnar piston (12) and the disc-shaped piston (23) in the piston cylinder (18) through the front cylinder water inlet pipe (14) and the front cylinder water inlet switch ball valve (13) to form a water-filled space; during the positive horizontal movement of the columnar piston (12) and the disc-shaped piston (23), the water in the water-filled space between the rear flange (24) of the piston cylinder (18) and the disc-shaped piston (23) is discharged outward through the rear cylinder water outlet switch ball valve (30) and the rear cylinder water outlet pipe (29), and at the same time, the air in the rear cylinder water outlet switch ball valve (30) and the rear cylinder water outlet pipe (29) flows out together with the discharged water, and finally the air in the rear cylinder water outlet switch ball valve (30) and the rear cylinder water outlet pipe (29) is completely discharged; 9) Close the front cylinder manual exhaust ball valve (16), the front cylinder water inlet switch ball valve (13), the rear cylinder water outlet switch ball valve (30) and the rear cylinder manual exhaust ball valve (25), and open the front cylinder water outlet switch ball valve (20), the front and rear cylinder water outlet pipe isolation ball valves (31) and the rear cylinder water inlet switch ball valve (28); 10) controls the servo motor (1) to rotate in the reverse direction to drive the reducer (2) to rotate in the same direction. The rotation of the servo motor (1) is decelerated by the reducer (2) to drive the lead screw (6) to rotate in the reverse direction. The reverse rotation of the lead screw is converted into reverse horizontal movement of the lead screw nut (10) through the cooperation of the lead screw (6) and the lead screw nut (10). The reverse horizontal movement of the lead screw nut (10) drives the slidable metal support (9) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the slidable metal support (9) drives the floating joint (11) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the floating joint (11) pulls the columnar piston (12) and the disc piston (23) to move in the reverse synchronous horizontal direction until the other end of the columnar piston (12) and the disc piston (23) reach the top of the piston cylinder (18); after the columnar piston (12) and the disc piston (23) move in the reverse direction, the piston cylinder (18) and the disc piston (23) move in the reverse direction. During the horizontal movement, the water in the high-level water tank (50) enters the water-filled space between the rear flange (24) of the piston cylinder (18) and the disc-shaped piston (23) through the rear cylinder water inlet pipe (27) and the rear cylinder water inlet switch ball valve (28); during the reverse synchronous horizontal movement of the columnar piston (12) and the disc-shaped piston (23), the water in the space between the piston cylinder front flange (17), the columnar piston (12) and the disc-shaped piston (23) in the piston cylinder (18) is discharged outward through the front cylinder water outlet switch ball valve (20) and the front cylinder water outlet pipe (19), and at the same time, the air in the front cylinder water outlet switch ball valve (20) and the front cylinder water outlet pipe (19) flows out together with the discharged water, and finally the air in the front cylinder water outlet switch ball valve (20), the front cylinder water outlet pipe (19) and the front and rear cylinder water outlet pipe isolation ball valves (31) are completely discharged; 11) Repeat steps 3), 4), 5) and 6) to completely remove the air in the space between the rear flange (24) of the piston cylinder (18) and the disc-shaped piston (23) and the air in the space between the front flange (17) of the piston cylinder (18), the columnar piston (12) and the disc-shaped piston (23) in the piston cylinder (18). 3. A method for calibrating the flow rate of a water meter using a wide range ratio water meter calibration standard device, the wide range ratio water meter calibration standard device comprising a piston device as a main standard and a peripheral system, a calibration device, a pressurizing system, a high-level water tank (50) and an exhaust system; The piston device and peripheral system as the main standard include a servo motor (1), a reducer (2), a reducer metal support (3), a coupling (4), a screw front metal support (5), a screw (6), a linear guide (7), a piston metal bracket (8), a slidable metal support (9), a screw nut (10), a floating joint (11), a cylindrical piston (12), a front cylinder water inlet switch ball valve (13), a front cylinder water inlet pipe (14), a front cylinder exhaust pipe (15), a front cylinder manual exhaust ball valve (16), a piston cylinder front flange (17), and a movable A plug cylinder (18), a front cylinder water outlet pipe (19), a front cylinder water outlet switch ball valve (20), a screw rear metal support (21), a piston metal support (22), a disc-shaped piston (23), a piston cylinder rear flange (24), a rear cylinder manual exhaust ball valve (25), a rear cylinder exhaust pipe (26), a rear cylinder water inlet pipe (27), a rear cylinder water inlet switch ball valve (28), a rear cylinder water outlet pipe (29), a rear cylinder water outlet switch ball valve (30), a front and rear cylinder water outlet pipe isolation ball valve (31), and a front and rear cylinder water outlet pipe isolation ball valve connecting pipe (32); The calibration device comprises a switch ball valve (33) in front of the meter clamp, a connecting pipe (56) in front of the meter clamp, a meter clamp (34), a front straight pipe section (35), an electromechanical conversion device (36) of the water meter to be inspected, a water meter to be inspected (37), a rear straight pipe section (38), a calibration device support frame (39), a manifold (40), a small-diameter back-pressure switch ball valve (41), a back-pressure switch ball valve (42) of the same diameter, a small-diameter back-pressure pipe (43), and a back-pressure pipe (44) of the same diameter; The pressurizing system comprises a pressurizing water pump outlet pipe (45), a pressure water pump rear switch ball valve (46), a pressurizing water pump (47), a pressure water pump front switch ball valve (48), and a pressurizing water pump inlet pipe (49); the pressurizing water pump outlet pipe (45) is fixedly connected to the small-diameter back pressure pipe (43) through a tee pipe; The exhaust system comprises an exhaust water inlet pipe (51), a switch ball valve (52) before the exhaust water pump, an exhaust water pump (53), a switch ball valve (54) after the exhaust water pump, and an exhaust water outlet pipe (55); The cylindrical piston (12), the piston cylinder front flange (17), the piston cylinder (18), the disc piston (23), and the piston cylinder rear flange (24) together constitute a double standard piston device; the cylindrical piston (12), the piston cylinder front flange (17), the piston cylinder (18), and the disc piston (23) together constitute a column-disc combination standard; the piston cylinder front flange (17) in the column-disc combination standard is fixedly installed at the front end of the piston cylinder (18), and an O-type sealing ring is used to seal between the piston cylinder (18) and the piston cylinder front flange (17); one end of the cylindrical piston (12) is fixedly connected to the floating joint (11), and the other end of the cylindrical piston (12) is fixedly connected to the disc piston (23), the disc piston (23) is located in the piston cylinder (18), and a Y-type sealing ring and a guide are installed between the disc piston (23) and the piston cylinder (18). The cylindrical piston (12) passes through the middle of the piston cylinder front flange (17), a part of which is located outside the piston cylinder (18) and the other part of which is located inside the piston cylinder (18). A certain water-filled space is reserved between the part of the cylindrical piston (12) located inside the piston cylinder (18) and the piston cylinder (18). A Y-shaped sealing ring is used to seal between the cylindrical piston (12) and the piston cylinder front flange (17). The Y-shaped sealing ring is fixedly mounted on the piston cylinder front flange (17). The front end, middle part and rear end of the cylindrical piston (12) are supported by the floating joint (11), the piston cylinder front flange (17) and the disc piston (23) respectively. The space in the piston cylinder (18) between the piston cylinder front flange (17), the cylindrical piston (12) and the disc piston (23) is a water-filled space. When working, the cylindrical piston (12) and the disc piston (23) push toward the piston cylinder front flange. When the piston cylinder (18) moves in the direction of rotation (17), the space between the front flange (17) of the piston cylinder, the cylindrical piston (12) and the disc-shaped piston (23) in the piston cylinder (18) is reduced. Since the cylindrical piston (12) and the front flange (17) of the piston cylinder, and the disc-shaped piston (23) and the piston cylinder (18) are sealed by Y-shaped sealing rings, the water in the water-filled space is compressed and discharged from the piston cylinder (18) through the front cylinder body water outlet pipe (19). The volume of water discharged from the piston cylinder (18) can be calculated based on the outer diameter of the cylindrical piston (12), the inner diameter of the piston cylinder (18) and the moving distance of the cylindrical piston (12) and the disc-shaped piston (23); the piston cylinder (18), the disc-shaped piston (23) and the piston cylinder rear flange (24) together form a disc-shaped standard device; the piston cylinder rear flange (24) in the disc-shaped standard device is fixedly mounted on the piston cylinder (18) ), an O-ring is used to seal the rear end of the piston cylinder (18) and the rear flange (24) of the piston cylinder; the disc-shaped standard and the column-disk combined standard share the disc-shaped piston (23); the space between the rear flange (24) of the piston cylinder and the disc-shaped piston (23) in the piston cylinder (18) is a water-filled space. During operation, the disc-shaped piston (23) moves toward the rear flange (24) of the piston cylinder, and the space between the rear flange (24) of the piston cylinder and the disc-shaped piston (23) in the piston cylinder (18) is reduced. Since the disc-shaped piston (23) and the piston cylinder (18) are sealed by a Y-ring, the water in the water-filled space is compressed and discharged from the piston cylinder (18) through the rear cylinder body water outlet pipe (29). The volume of water discharged from the piston cylinder (18) can be calculated based on the inner diameter of the piston cylinder (18) and the moving distance of the disc-shaped piston (23); It is characterized by comprising the following steps: A. Calibration of large flow points a) installing the water meter (37) to be inspected between the front straight pipe section (35) and the rear straight pipe section (38); b) controlling the servo motor (1) to rotate in the reverse direction to drive the reducer (2) to rotate in the same direction. The rotation of the servo motor (1) is decelerated by the reducer (2) to drive the lead screw (6) to rotate in the reverse direction. The reverse rotation of the lead screw is converted into reverse horizontal movement of the lead screw nut (10) through the cooperation between the lead screw (6) and the lead screw nut (10). The reverse horizontal movement of the lead screw nut (10) drives the slidable metal support (9) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the slidable metal support (9) drives the floating joint (11) to move in the reverse synchronous horizontal direction. The reverse synchronous horizontal movement of the floating joint (11) pulls the columnar piston (12) and the disc piston (23) to move in the reverse synchronous horizontal direction until the other end of the columnar piston (12) and the disc piston (23) reach the top of the piston cylinder (18); c) closing the isolation ball valves (31) of the front and rear cylinder water outlet pipes and the switch ball valve (30) of the rear cylinder water outlet; opening the switch ball valve (33) in front of the meter clamp, the small-diameter back pressure switch ball valve (41), the same-diameter back pressure switch ball valve (42), the switch ball valve (52) in front of the exhaust water pump and the switch ball valve (54) in the rear of the exhaust water pump, starting the exhaust water pump (53) to connect the rear cylinder water outlet pipe (29), the switch ball valve (33) in front of the meter clamp, and the switch ball valve (54) in front of the meter clamp. The air in the pipeline (56), the meter clamp (34), the front straight pipe section (35), the water meter to be inspected (37), the rear straight pipe section (38), the manifold (40), the small-diameter back-pressure switch ball valve (41), the same-diameter back-pressure switch ball valve (42), the small-diameter back-pressure pipeline (43), the same-diameter back-pressure pipeline (44), the exhaust water inlet pipeline (51), the exhaust water pump front switch ball valve (52), the exhaust water pump (53), and the exhaust water outlet pipeline (55) is completely exhausted; d) Close the front cylinder manual exhaust ball valve (16), the front cylinder water outlet switch ball valve (20), the front and rear cylinder water outlet pipe isolation ball valves (31), the rear cylinder manual exhaust ball valve (25), the rear cylinder water inlet switch ball valve (28), the exhaust water pump rear switch ball valve (54), and the small-diameter back pressure switch ball valve (41); open the front cylinder water inlet switch ball valve (13), the rear cylinder water outlet switch ball valve (30), the meter clamp front switch ball valve (33), and the same-diameter back pressure switch ball valve (42); e) controlling the servo motor (1) to accelerate forward to a speed corresponding to the required calibration flow rate and then maintain a uniform speed of rotation; at the same time, the forward rotation of the servo motor (1) is decelerated by a certain reduction ratio of the reducer (2) to drive the lead screw (6) to rotate forward, and the rotation of the lead screw (3) is converted into horizontal movement of the columnar piston (12) and the disc-shaped piston (23) through the cooperation between the lead screw (3) and the lead screw nut (10), the slidable metal support (9), the floating joint (11), the columnar piston (12) and the disc-shaped piston (23); the horizontal movement of the columnar piston (12) and the disc-shaped piston (23) on the one hand causes the water in the high-level water tank (50) to be sucked into the space between the front flange (17) of the piston cylinder, the columnar piston (12) and the disc-shaped piston (23) in the piston cylinder (18) through the front cylinder water inlet pipe (14) and the front cylinder water inlet switch ball valve (13). The space is a water-filled space. On the other hand, the water in the water-filled space between the rear flange (24) of the piston cylinder and the disc-shaped piston (23) is discharged outward through the rear cylinder water outlet switch ball valve (30) and the rear cylinder water outlet pipe (29) at the required calibration flow rate under the push of the disc-shaped piston (23), and enters the high-level water tank (50) after passing through the switch ball valve (33) in front of the meter clamp, the connecting pipe (56) in front of the meter clamp, the meter clamp (34), the front straight pipe section (35), the water meter to be inspected (37), the rear straight pipe section (38), the manifold (40), the same-diameter back-pressure switch ball valve (42), and the same-diameter back-pressure pipe (44); after the cylindrical piston (12) and the disc-shaped piston (23) are correspondingly changed from accelerated horizontal movement to uniform horizontal movement, the time frequency recorder starts to accumulate the frequency of the driving servo motor (1) and simultaneously records the frequency accumulation start time t ₁ ; after the cylindrical piston (12) and the disc piston (23) change from accelerated horizontal movement to uniform horizontal movement respectively, the time frequency recorder starts to accumulate the frequency signal output by the inspected water meter (37), and records the frequency accumulation start time _t'1 ; when the time frequency recorder accumulates the frequency signal output by the inspected water meter (37) to the minimum number of frequency signals, the time frequency recorder stops accumulating the frequency signal output by the inspected water meter (37), and records the accumulation stop time _t'2 and the accumulated number N' of frequency signals; after the time frequency recorder stops accumulating the frequency signal output by the inspected water meter (37), the time frequency recorder then stops accumulating the frequency signal output by the servo motor (1), and records the accumulation stop time _t2 and the accumulated number N of frequency signals; f) According to the cumulative number N' of the frequency signal of the inspected water meter (37) recorded by the time frequency recorder and the corresponding cumulative start time _t'1 and end time _t'2 , the average flow rate of the inspected water meter (37) within the frequency signal accumulation time period is calculated according to formula (1): Q＝(P×N')/( _t'2 - _t'1 ) (1) Wherein, Q is the average flow rate in the time period during which the frequency signals output by the inspected water meter (37) are accumulated; P is the accumulated amount of water represented by each frequency signal when water flows through the inspected water meter (37); g) According to the cumulative number N of the frequency signals of the servo motor (1) recorded by the time frequency recorder and the corresponding cumulative start time _t1 and end time _t2 , the average flow rate of the water meter calibration standard device within the frequency signal accumulation time period is calculated according to formula (2): q＝πD ² ipωN/[4(t ₂ - t ₁ )] (2) Wherein, q is the average flow rate of the water meter calibration standard device within the frequency signal accumulation time period; π is the pi; D is the inner diameter of the piston cylinder (18); i is the speed ratio of the reducer (2); p is the lead of the screw (6); ω is the angle of rotation of the servo motor (1) when the servo motor (1) receives each frequency signal; h) According to formula (3), the indication error of the inspected flow point of the inspected water meter (37) is calculated as follows: E＝(Q-q)/q×100％ (3) Where, E is the indication error of the inspected flow point of the inspected water meter (37); i) judging whether the servo motor (1) can continue to rotate in the same direction according to the next flow point to be checked of the water meter (37), its check time and the distance that the disc-shaped piston (23) has moved horizontally: if it can continue to rotate in the same direction, repeating steps e) to h) to complete the check of the next flow point; if it can no longer continue to rotate in the same direction, first executing step b), and then executing steps d) to h) to complete the check of the next flow point; j) Repeat step i) to complete the calibration of other large flow points of the water meter (37) under inspection; B. Calibration of small flow points a') judging whether the servo motor (1) can perform reverse rotation according to the small flow rate verification point of the water meter (37) under inspection, its verification time and the distance that the disc-shaped piston (23) has been running horizontally: if it can perform reverse rotation, executing steps c') to g'); if it cannot perform reverse rotation, executing step b), and then executing steps c') to g'); b') repeating step a') to complete the calibration of other small flow points of the water meter (37) under inspection; c') closing the front cylinder manual exhaust ball valve (16), the front cylinder water inlet switch ball valve (13), the rear cylinder manual exhaust ball valve (25), the rear cylinder water outlet switch ball valve (30), the same diameter back pressure switch ball valve (42), and the exhaust water pump rear switch ball valve (54); opening the front cylinder water outlet switch ball valve (20), the rear cylinder water inlet switch ball valve (28), the front and rear cylinder water outlet pipe isolation ball valves (31), the small-diameter back pressure switch ball valve (41), the pressure water pump rear switch ball valve (46), and the pressure water pump front switch ball valve (48); d') controlling the servo motor (1) to accelerate in the reverse direction to a speed corresponding to the required calibration flow rate and then maintain a uniform speed of rotation. At the same time, the reverse rotation of the servo motor (1) is decelerated by a certain reduction ratio of the reducer (2) to drive the lead screw (6) to rotate in the reverse direction. The rotation of the lead screw (3) is converted into horizontal movement of the columnar piston (12) and the disc-shaped piston (23) through the cooperation between the lead screw (3) and the lead screw nut (10), the slidable metal support (9), the floating joint (11), the columnar piston (12) and the disc-shaped piston (23). The horizontal movement of the columnar piston (12) and the disc-shaped piston (23) transfers the water in the high-level water tank (50) through the rear cylinder body. The water inlet pipe (27) and the rear cylinder water inlet switch ball valve (28) suck water into the water-filled space between the rear flange (24) of the piston cylinder (18) and the disc-shaped piston (23). On the other hand, the water in the water-filled space between the front flange (17) of the piston cylinder in the piston cylinder (18), the columnar piston (12) and the disc-shaped piston (23) is pushed by the disc-shaped piston (23) to be discharged outward at a required calibration flow rate through the front cylinder water outlet switch ball valve (20), the front cylinder water outlet pipe (19), and the front and rear cylinder water outlet pipe isolation ball valves (31), and passes through the meter clamp front switch ball valve (33), the meter clamp front connecting pipe (56), the meter clamp (34), the front straight pipe section ( 35), the inspected water meter (37), the rear straight pipe section (38), the manifold (40), the small-diameter back pressure switch ball valve (41), the small-diameter back pressure pipe (43), and then enter the high-level water tank (50); while controlling the servo motor (1) to accelerate the rotation in the reverse direction, the pressure pump (47) is started. Under the action of the pressure pump (47), the water in the high-level water tank (50) passes through the pressure pump inlet pipe (49), the pressure pump front switch ball valve (48), the pressure pump (47), the pressure pump rear switch ball valve (46), the pressure pump outlet pipe (45), and then enters the small-diameter back pressure pipe (43), and finally flows from the small-diameter back pressure pipe (43) into the high-level water tank (5 0), when the water flow supplied by the pressure water pump (47) flows into the high-level water tank (50) via the small-diameter back pressure pipe (43), the water flow in the small-diameter back pressure pipe (43) will quickly generate a back pressure exceeding the minimum back pressure required for the water meter (37) to be inspected during calibration, and the back pressure is transmitted to the water meter (37) to be inspected through the rear straight pipe section (38), and finally quickly generates a constant back pressure exceeding the minimum back pressure required for the water meter (37) to be inspected in the rear straight pipe section (38); after a constant back pressure exceeding the minimum back pressure required for the water meter (37) to be inspected is generated in the rear straight pipe section (38), the time frequency recorder starts to accumulate the frequency of the drive servo motor (1) to rotate, and simultaneously records the frequency accumulation start time t ₁ ; after the time-frequency recorder starts to accumulate the frequency of the drive servo motor (1) to rotate, the time-frequency recorder starts to accumulate the frequency signal output by the inspected water meter (37), and records the frequency accumulation start time _t'1 ; when the time-frequency recorder accumulates the frequency signal output by the inspected water meter (37) to a minimum number of frequency signals, the time-frequency recorder stops accumulating the frequency signal output by the inspected water meter (37), and records the accumulation stop time _t'2 and the accumulated number N' of frequency signals; after the time-frequency recorder stops accumulating the frequency signal output by the inspected water meter (37), the time-frequency recorder then stops accumulating the frequency signal output by the servo motor (1), and records the accumulation stop time _t'2 and the accumulated number N of frequency signals; e') executing step f); f') According to the cumulative number N of the frequency signals of the servo motor (1) recorded by the time frequency recorder and the corresponding cumulative start time _t1 and end time _t2 , the average flow rate of the water meter calibration standard device within the frequency signal accumulation time period is calculated according to formula (4): q＝πipωN (D ² -D ₁ ² )/[4(t ₂ - t ₁ )] (4) In the formula, q is the average flow rate of the water meter calibration standard device within the frequency signal accumulation time period; π is the pi; i is the speed ratio of the reducer (2); p is the lead of the screw (6); ω is the angle of rotation of the servo motor (1) when the servo motor (1) receives each frequency signal; D is the inner diameter of the piston cylinder (18); _D1 is the outer diameter of the cylindrical piston (12); g') execute step h).