JP5438577B2 - Ultrasonic flow meter - Google Patents

Description

  The present invention relates to an ultrasonic flow meter, and more particularly to an ultrasonic flow meter that measures the flow rate of a fluid under measurement by transmitting and receiving ultrasonic waves to and from a pipeline through which the fluid under measurement flows.

  For example, a pipe that supplies a fluid such as city gas is provided with a control valve that controls the secondary pressure on the downstream side and a flow meter that measures the flow rate of the fluid flowing in the pipe. The control valve adjusts the secondary pressure on the downstream side to be a preset pressure by changing the valve opening according to an instruction from the pressure setting unit. For example, the consumption of city gas tends to fluctuate depending on the time of day, and tends to increase at the time of lunch or dinner, and to decrease at other times. In winter when the temperature is low, gas consumption by the gas water heater increases, and in summer when the temperature is high, the gas consumption tends to decrease. Therefore, in the pressure setting unit, the set pressure (target pressure) for each time zone is stored in advance in the storage unit, and the set pressure (target pressure) in the current time zone is read from the storage unit to drive the control valve. The control signal for valve opening degree control is output to the part, and the downstream secondary pressure is adjusted to a preset pressure (for example, refer to Patent Document 1).

  On the other hand, as a flow meter that measures the flow rate of a fluid flowing in a pipe, an ultrasonic flow meter that measures the flow rate of a fluid to be measured by transmitting and receiving ultrasonic waves to and from a pipeline through which the fluid flows is used. This ultrasonic flowmeter is expected to save power, so when the flow rate is stable, this mode saves power by increasing the transmission interval of ultrasonic waves from the upstream ultrasonic sensor (power saving mode). When the flow rate fluctuation is measured, the ultrasonic transmission interval is shortened and the mode is switched to a mode (precision measurement mode) in which the flow rate is measured with higher accuracy (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 5-17685 JP 2004-340703 A

  However, in the conventional ultrasonic flowmeter according to Patent Document 2, when the ultrasonic flowmeter measures the flow fluctuation, the transmission interval is changed so as to shorten the ultrasonic transmission interval. At that time, the flow rate is measured with a long transmission interval, so there is a problem that the flow rate at the time of flow rate variation cannot be measured accurately.

  In view of the above circumstances, an object of the present invention is to provide an ultrasonic flowmeter that solves the above problems.

In order to solve the above problems, the present invention has the following means.
(1) The present invention provides a flow meter body provided in a pipe having a control valve that changes a valve opening based on a preset change timing of a set pressure;
An upstream ultrasonic sensor provided on the upstream side in the flow path of the flow meter body;
A downstream ultrasonic sensor provided downstream in the flow path of the flow meter body;
Transmitter driving means for outputting a drive signal to the upstream ultrasonic sensor or the downstream ultrasonic sensor so as to transmit ultrasonic waves from the upstream ultrasonic sensor or the downstream ultrasonic sensor;
Transmission interval changing means for changing the transmission interval of ultrasonic waves transmitted from the upstream ultrasonic sensor or the downstream ultrasonic sensor;
Based on the time difference between the ultrasonic reception signals output from the upstream ultrasonic sensor and the downstream ultrasonic sensor, flow rate measuring means for measuring the flow rate of the fluid flowing in the flow path of the flow meter body,
In an ultrasonic flowmeter having
The transmission interval changing means outputs the drive signal output time by the transmitter driving means so that the transmission intervals of the upstream ultrasonic sensor and the downstream ultrasonic sensor become short when the set pressure change timing is reached. The interval is changed, and the output time interval of the drive signal by the transmitter driving means is changed so that the transmission interval of the upstream ultrasonic sensor becomes longer when the set pressure is stable.
(2) The transmission interval changing means of the present invention is configured such that the transmission intervals of the upstream ultrasonic sensor and the downstream ultrasonic sensor are shorter than a reference time interval based on the change of the valve opening of the control valve. The output time interval of the driving signal by the transmitter driving means is changed.
(3) In the transmission interval changing means of the present invention, the transmission intervals of the upstream ultrasonic sensor and the downstream ultrasonic sensor are stepwise in accordance with the magnitude of pressure fluctuation caused by changing the valve opening of the control valve. The output time interval of the driving signal by the transmitter driving means is changed so as to be shorter.

  According to the present invention, the output time interval of the drive signal by the transmitter driving means is changed so that the transmission interval of the upstream ultrasonic sensor and the downstream ultrasonic sensor is shortened when the set pressure change timing is reached, When the set pressure is stable, the output time interval of the drive signal by the transmitter driving means is changed so that the transmission interval of the upstream ultrasonic sensor and the downstream ultrasonic sensor becomes longer. It is possible to switch so that the transmission interval between the ultrasonic sensor and the downstream ultrasonic sensor is shortened, and the flow rate can be measured with high accuracy when the flow rate fluctuates without time delay.

It is a block diagram which shows typically the pressure regulation system by which the ultrasonic flowmeter and control valve by this invention were distribute | arranged to piping. It is a figure which illustrates the setting pressure fluctuation pattern controlled by a control valve. It is a figure which shows the transmission interval of the ultrasonic wave according to a flow volume. It is a flowchart for demonstrating the control processing which the control part of an ultrasonic flowmeter performs. It is a block diagram which shows typically the pressure adjustment system of the modification 1. FIG. It is a block diagram which shows the pressure adjustment system of the modification 2 typically.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram schematically showing a pressure control system in which an ultrasonic flowmeter and a control valve according to the present invention are arranged in a pipe. As shown in FIG. 1, a pressure control system 50 including a control valve 20, an ultrasonic flow meter 30, and a pressure sensor 40 is provided in the pipe 10 that supplies city gas.

  The control valve 20 includes a governor body 22 that controls the pressure and flow rate of a gas (fluid) that flows through a flow path that communicates with the pipe 10, a pilot section 24 that includes a diaphragm that drives the valve section of the governor body 22, and a pilot section. 24 includes a pressure control unit 26 that outputs a control signal for controlling the valve opening degree.

  The pressure control unit 26 includes a clock that detects the current time and a storage unit 28 that stores preset pressure data in advance because the gas consumption consumed on the downstream side varies depending on the time zone. And if the set pressure at that time is read from the memory | storage part 28, the control signal which controls the valve opening degree of the governor main body 22 will be output.

  As a result, the governor body 22 performs pressure control based on the control signal input to the pilot section 24 so that the downstream secondary pressure becomes the set pressure. Therefore, the secondary pressure on the downstream side of the control valve 20 is controlled to a predetermined set pressure according to the expected gas consumption.

  The ultrasonic flow meter 30 includes a flow meter main body 32 in which a flow path 31 communicated with the pipe 10 is formed, an upstream ultrasonic sensor 34, a downstream ultrasonic sensor 36, and a flow control unit 38. Have. The upstream ultrasonic sensor 34 is provided so as to be exposed on the inner wall on the upstream side of the flow channel 31, and is attached to the inner wall of the flow channel so that the transmission / reception surface faces the downstream side. Further, the downstream ultrasonic sensor 36 is provided so as to be exposed on the inner wall on the downstream side of the flow channel 31 and is attached to the inner wall of the flow channel so that the transmission / reception surface faces the upstream side.

  The flow rate control unit 38 of the ultrasonic flow meter 30 propagates through the fluid from the upstream ultrasonic sensor 34 toward the downstream and receives the ultrasonic propagation time from the downstream ultrasonic sensor 36 to the downstream ultrasonic sensor 36. Since the time difference from the ultrasonic wave propagation time until it propagates in the fluid upstream from the acoustic wave sensor 36 and is received by the upstream ultrasonic sensor 34 becomes a value proportional to the flow rate, the flow velocity and flow rate are determined from the detected time difference. Is calculated. Therefore, the upstream ultrasonic sensor 34 and the downstream ultrasonic sensor 36 transmit and receive with respect to the extending direction (axial direction) of the flow path 31 so that the ultrasonic wave propagating in the fluid is easily affected by the flow velocity. It is arranged in a V shape so that the center line of the surface is inclined at a predetermined angle. Moreover, the attachment position of the upstream ultrasonic sensor 34 and the downstream ultrasonic sensor 36 is not limited to this, and the upstream ultrasonic sensor 34 and the downstream ultrasonic sensor 36 may be inclined with respect to the flow path 31 and arranged opposite to each other on a straight line.

In the ultrasonic flow meter 30, the flow rate is measured based on the following equation. Here, the following equation is obtained from the time difference Δt between the propagation time t1 from the upstream ultrasonic sensor 34 to the downstream ultrasonic sensor 36 and the propagation time t2 from the downstream ultrasonic sensor 36 to the upstream ultrasonic sensor 34. It is done.
t1 = L / (C + V cos θ) (Formula 1)
t2 = L / (C−Vcos θ) (Expression 2)
From equations 1 and 2, the flow velocity V (m / s) can be obtained from the following equation.
V = L / (2 cos θ) · {(1 / t1) − (1 / t2)} (Expression 3)
L is the distance (m) from the upstream ultrasonic sensor 34 to the downstream ultrasonic sensor 36, θ is the angle formed by the propagation axis of the ultrasonic wave and the center line (or the inner wall of the flow path) of the flow path 31, C is the speed of sound of gas (m / s).

  The flow rate control unit 38 of the ultrasonic flowmeter 30 includes an ultrasonic sensor drive unit (transmitter drive unit) 41, a transmission interval change unit (transmission interval change unit) 42, a flow rate measurement unit (flow rate measurement unit) 44, It has a secondary pressure monitoring unit 46, a storage unit 48, and a battery 49 as a power source.

  The ultrasonic sensor drive unit 41 outputs drive signals to the upstream ultrasonic sensor 34 and the downstream ultrasonic sensor 36 at a predetermined time interval, and the flow path 31 from the upstream ultrasonic sensor 34 and the downstream ultrasonic sensor 36. Ultrasonic waves are transmitted to the fluid flowing through.

  The transmission interval changing unit 42 outputs a control signal for changing the transmission interval of the ultrasonic wave transmitted from the upstream ultrasonic sensor 34 when there is a pressure fluctuation or when there is no pressure fluctuation.

  The flow rate measuring unit 44 transmits the ultrasonic wave from the upstream ultrasonic sensor 34 to the propagation time t1 until the ultrasonic reception signal is output from the downstream ultrasonic sensor 36, and the ultrasonic wave from the downstream ultrasonic sensor 36. The flow rate of the fluid flowing in the flow path 31 is measured by performing the calculation based on the above equation 3 based on the time difference Δt with the propagation time t2 from when the signal is transmitted until the ultrasonic reception signal is output from the upstream ultrasonic sensor 34. To do.

  The secondary pressure monitoring unit 46 monitors the pressure change of the secondary pressure controlled by the control valve 20 based on the detection signal from the pressure sensor 40, and when the secondary pressure changes by a predetermined value or more, the transmission interval changing unit 42 outputs a pressure fluctuation detection signal. Thereby, the transmission interval changing unit 42 outputs a control signal for instructing the ultrasonic sensor driving unit 41 to change the transmission interval so as to shorten the transmission interval.

  Further, when the ultrasonic flowmeter 30 is disposed downstream from the control valve 20, the secondary pressure monitoring unit 46 may detect the time when the pressure sensor 40 cannot detect the pressure fluctuation or the time for the detection. In consideration of the delay, the set pressure fluctuation pattern data of the control valve 20 stored in the storage unit 48 is read at predetermined time intervals. It is also possible to provide pressure sensors 40 on both the upstream side and the downstream side of the ultrasonic flow meter 30 to detect pressure fluctuations and flow rate fluctuations from the difference between both pressure detection values (pressure difference).

  Therefore, the secondary pressure monitoring unit 46 can output a pressure variation detection signal to the transmission interval changing unit 42 based on the data of the set pressure variation pattern, and the pressure control operation by the control valve 20 is performed. At the same time, the transmission interval of ultrasonic waves can be changed. That is, since the control valve 20 is installed upstream of the ultrasonic flow meter 30, it is possible to change the ultrasonic transmission interval before the pressure at the installation location of the ultrasonic flow meter 30 fluctuates.

  The ultrasonic sensor driving unit 41 outputs to the upstream ultrasonic sensor 34 so that the transmission interval (cycle) is set in advance according to the change timing of the set pressure based on the control signal from the transmission interval changing unit 42. The time interval (cycle) of the drive signal to be changed is shortened. Note that the transmission interval of the ultrasonic wave transmitted from the upstream ultrasonic sensor 34 is such that a drive signal is output at a long time interval longer than the standard time used in normal flow rate measurement to extend the replacement time of the battery 49. There are a power saving mode and a precision measurement mode in which a drive signal is output at a short time interval shorter than the standard time. In the present embodiment, by switching to the power saving mode or the precision measurement mode, when the pressure fluctuation is stable, the power saving mode is switched to extend the life of the battery that drives the ultrasonic flowmeter 30. If pressure fluctuations occur, switch to the precise measurement mode and control to accurately measure the flow rate during pressure fluctuations.

  In the present embodiment, a standard measurement mode in which an ultrasonic transmission interval is set at a standard time (a predetermined normal time interval) is provided between the power saving mode and the precise measurement mode. .

  FIG. 2 is a diagram illustrating a set pressure fluctuation pattern controlled by the control valve. As shown in FIG. 2, the diagram A is an example of a set pressure fluctuation pattern stored in the pressure control unit 26 of the control valve 20. In this embodiment, the set pressure variation pattern is also stored in the storage unit 48 of the ultrasonic flow meter 30.

An arrow B from the upper side to the lower side of the diagram A indicates the transmission timing of the ultrasonic wave.
The interval between arrows B indicates the transmission interval. For example, in the diagram A, the time zones T1 to T2, T3 to T4, and T5 to T6 have a constant pressure and are stable, so the transmission interval is set to the long time interval TA (power saving measurement mode). ). Moreover, since the pressure fluctuates in the time zones T2 to T3 and T4 to T5, the transmission interval is set to the standard time interval TB (<TA) (standard measurement mode). In addition, since the pressure fluctuates abruptly in the time period T4 to T5, the transmission interval is set to a time interval TC (<TB) shorter than the standard time TB (precise measurement mode). Moreover, the arrow C heading upward from the lower side of the diagram A indicates the change timing of the set pressure.

  FIG. 3 is a diagram showing the transmission interval of ultrasonic waves according to the flow rate. As shown in FIG. 3, the diagram D shows the change pattern of the measured value of the flow velocity (flow rate) of the fluid flowing through the flow path 31 of the ultrasonic flow meter 30 according to the set pressure. Further, in the diagram D, since the transmission interval of the ultrasonic wave is controlled to change according to the measured flow rate, the pressure is constant and stable in the time zones T1 to T2, T3 to T4, and T5 to T6. Therefore, the transmission interval is set to TA = 1.0 seconds longer than the standard time (power saving measurement mode). Further, in the time zones T2 to T3 in which the pressure and the flow rate gradually change, the transmission interval is set to the same standard time TB = 0.5 seconds (standard measurement mode). Further, in the time periods T4 to T5 in which the pressure and the flow rate suddenly change, the transmission interval is set to TC = 0.2 seconds shorter than the standard time (precise measurement mode).

  FIG. 4 is a flowchart for explaining a control process executed by the control unit of the ultrasonic flowmeter. As shown in FIG. 4, the control unit 38 checks whether or not the current time is the time of the pressure change timing from the data of the set pressure fluctuation pattern stored in the storage unit 48 in S11.

  In S11, when the current time is not the time of the pressure change timing (in the case of NO), the set pressure is stable without fluctuation and control of pressure fluctuation (valve opening change control) by the control valve 20 is performed. It is determined that there is not, and the process proceeds to S12.

  In S <b> 12, it is checked whether or not the current time is an ultrasonic transmission timing for performing flow rate measurement by the ultrasonic flow meter 30. In S12, when the current time is not the transmission timing of ultrasonic waves in the currently set flow rate measurement mode (power saving measurement mode, standard measurement mode, or precise measurement mode) (in the case of NO), the above-mentioned S11 Returning to the process, the timing monitoring process of S11 and S12 is repeated.

  In S12, when the current time is the transmission timing of the ultrasonic wave in the currently set flow measurement mode (in the case of YES), the process proceeds to S13, and the ultrasonic wave is transmitted from the upstream ultrasonic sensor 34. The time difference t1 between the transmission time and the reception time when the ultrasonic reception signal is output from the downstream ultrasonic sensor 36 is measured.

  In the next S14, the time difference t2 between the transmission time at which the ultrasonic wave is transmitted from the downstream ultrasonic sensor 36 and the reception time at which the ultrasonic reception signal is output from the upstream ultrasonic sensor 34 is measured.

  Subsequently, the process proceeds to S15, and the flow velocity V of the fluid flowing through the flow path 31 is calculated based on the time differences t1 and t2 measured as described above and the above-described equation 3. In S16, an instantaneous flow rate Q per unit time is calculated from the flow velocity V.

  In the next S17, the flow rate fluctuation rate ΔQa is calculated from the difference between the instantaneous flow rate Q measured as described above and the target flow rate based on the set pressure of the control valve 20. Subsequently, the process proceeds to S18, and it is checked whether or not the flow rate fluctuation rate ΔQa is almost zero (Qa≈0). In S18, when the flow rate fluctuation rate ΔQa is almost zero (Qa≈0) (in the case of YES), since the flow rate is almost stable, the process proceeds to S19, and the ultrasonic transmission interval is set from the standard time interval TB. Also, a long time interval TA (power saving measurement mode) is set. Thereafter, the process returns to S11 and the processes after S11 are repeated.

  In S18, when the flow rate fluctuation rate ΔQa is almost zero or more (Qa> 0) (in the case of NO), the flow rate fluctuation is unstable and the process proceeds to S20, where the flow rate fluctuation rate ΔQa is predetermined. It is checked whether the flow rate fluctuation rate ΔQb or more. In S20, when the flow rate variation rate ΔQa is equal to or greater than the predetermined flow rate variation rate ΔQb (in the case of YES), the pressure variation due to the control of the valve opening degree of the control valve 20 arranged on the upstream side of the ultrasonic flow meter 30 is detected. Therefore, the process proceeds to S21, and the ultrasonic transmission interval is set to a time interval TC (precise measurement mode) shorter than the standard time interval TB. As a result, it is possible to accurately measure the flow rate change accompanying the pressure fluctuation. Thereafter, the process returns to S11 and the processes after S11 are repeated.

  In S20, when the flow rate variation rate ΔQa is not equal to or greater than the predetermined flow rate variation rate ΔQb (in the case of NO), the process proceeds to S22, and the ultrasonic transmission interval is set to the standard time interval TB (standard measurement mode). Thereafter, the process returns to S11 and the processes after S11 are repeated.

  Thus, even when the current time is not the pressure change timing from the data of the set pressure fluctuation pattern stored in the storage unit 48, power saving is performed based on the magnitude of the flow rate fluctuation rate of the flow rate measured by the ultrasonic flow meter 30. Since any one of the measurement mode, the standard measurement mode, and the precise measurement mode can be selected and the transmission interval can be set to the optimum value, when the flow rate is stable, the transmission interval can be set to TA to save power and the battery 49 When the flow rate variation rate is greater than or equal to a predetermined value, the time interval TC (precise measurement mode) can be set to accurately measure the flow rate variation.

  In S11, when the current time is the time of the pressure change timing (in the case of YES), the process proceeds to S23, where the pre-change pressure at the current time is determined from the set pressure fluctuation pattern data stored in the storage unit 48. The pressure difference ΔPa is calculated from the difference between PB and the changed pressure PA. In the next S24, it is checked whether or not the pressure difference ΔPa calculated in S23 is larger than a predetermined pressure difference ΔPb (pressure difference threshold). In S24, when the pressure difference ΔPa calculated in S23 is larger than a predetermined pressure difference ΔPb (pressure difference threshold value) set in advance (in the case of YES), the process proceeds to S25, and the ultrasonic transmission interval is set to be longer than the standard time interval. A short time interval TC (precision measurement mode) is used. As a result, it is possible to accurately measure the flow rate change accompanying the pressure fluctuation.

  In S24, when the pressure difference ΔPa calculated in S23 is smaller than the predetermined pressure difference ΔPb (pressure difference threshold) set in advance (in the case of NO), the flow rate fluctuation is small. Is a standard time interval TB (standard measurement mode).

  In the next S27 to S30, the flow velocity V of the fluid flowing through the flow path 31 is calculated based on the time differences t1 and t2 and the above-described equation 3 in the same manner as the processing of S13 to S16 described above, Is calculated. Thereafter, the process returns to S11 and the processes after S11 are repeated.

  As described above, when the current time is the pressure change timing from the set pressure fluctuation pattern data stored in the storage unit 48, either the power saving measurement mode or the precise measurement mode is selected based on the magnitude of the pressure difference ΔPa. And the transmission interval can be set before the flow rate fluctuates, so that the transmission interval change timing is prevented from being delayed with respect to the flow rate variation, and the transmission interval is TA when the flow rate is stable. As a result, the replacement time of the battery 49 can be extended by saving power.

  Further, the transmission interval of the upstream ultrasonic sensor 34 and the downstream ultrasonic sensor 36 is shortened in a stepwise manner from TA → TB → TC in accordance with the magnitude of pressure fluctuation due to the change in the valve opening of the control valve 20. It is also possible to change the output time interval of the drive signal by the ultrasonic sensor drive unit 41 stepwise.

  Here, a modified example will be described.

  FIG. 5 is a configuration diagram schematically illustrating a pressure adjustment system according to the first modification. In FIG. 5, the same portions as those in FIG. 1 described above are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 5, in the pressure adjustment system 60 of the first modification, the pressure control unit 26 of the control valve 20 and the flow rate control unit 38 of the ultrasonic flowmeter 30 are communicably connected via a communication line 62. ing. Therefore, the flow rate control unit 38 can read the pressure change timing from the set pressure fluctuation pattern data stored in the storage unit 28 of the pressure control unit 26. Note that the pressure control unit 26 and the flow rate control unit 38 each have a built-in wired or wireless communication device, and are set so that data communication can be performed at predetermined intervals.

  The flow rate control unit 38 executes the above-described control process (see the flowchart of FIG. 4) based on the pressure change timing signal transmitted from the pressure control unit 26.

  In the first modification, the flow rate control unit 38 does not need to store the data of the set pressure fluctuation pattern. For example, even when the data of the set pressure change pattern is changed, the data is stored in the storage unit 28 of the pressure control unit 26. Since only the stored data of the set pressure fluctuation pattern need be updated, it is advantageous when the downstream gas consumption changes from the expected value and is corrected.

  FIG. 6 is a configuration diagram schematically illustrating a pressure adjustment system according to a second modification. In FIG. 6, the same portions as those in FIG. 1 described above are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 6, in the pressure adjustment system 70 of the second modification, the host computer 82 provided in the management center 80 that manages the control of the plurality of control valves 20 is connected to each control valve via the communication lines 84 and 86. The pressure control unit 26 and the flow rate control unit 38 of the ultrasonic flowmeter 30 are communicably connected. Note that the pressure control unit 26 and the flow rate control unit 38 each have a built-in wired or wireless communication device, and are set so that data communication with the host computer 82 can be performed at predetermined intervals.

  The database 83 of the host computer 82 stores data of a plurality of control valves 20 (set pressure fluctuation pattern data) installed in the area in charge. The pressure control unit 26 controls the valve opening so that the secondary pressure becomes the set pressure indicated by the control signal from the host computer 82. Further, the flow rate control unit 38 executes the above-described control process (see the flowchart of FIG. 4) based on the pressure change timing signal transmitted from the host computer 82.

  In the second modification, a plurality of control valves 20 and a plurality of ultrasonic flow meters 30 installed in each region can be collectively controlled according to fluctuations in gas consumption in each region. 20 and the operation of individually updating the data in the storage unit of each ultrasonic flow meter 30 are not required, and the maintenance work can be greatly simplified.

  In the above-described embodiment, the description has been made using the piping path for supplying the city gas. However, the present invention is not limited to this, and fluids other than city gas (gases such as nitrogen and hydrogen, liquids such as water and oil, and fluids having viscosity) Of course, the present invention can also be applied to a system for controlling the pressure and flow rate of the piping path for supplying the gas.

DESCRIPTION OF SYMBOLS 10 Pipe 20 Control valve 22 Governor main body 24 Pilot part 26 Pressure control part 28 Memory | storage part 30 Ultrasonic flowmeter 32 Flowmeter main body 34 Upstream ultrasonic sensor 36 Downstream ultrasonic sensor 38 Flow control part 40 Pressure sensor 41 Ultrasonic sensor Drive unit 42 Transmission interval changing unit 44 Flow rate measuring unit 46 Secondary pressure monitoring unit 48 Storage units 50, 60, 70 Pressure control system 62 Communication line 80 Management center 82 Host computer 83 Database 84, 86 Communication line

Claims (3)

A flow meter body provided in a pipe having a control valve for changing the valve opening based on a preset change timing of the set pressure;
An upstream ultrasonic sensor provided on the upstream side in the flow path of the flow meter body;
A downstream ultrasonic sensor provided downstream in the flow path of the flow meter body;
Transmitter driving means for outputting a drive signal to the upstream ultrasonic sensor or the downstream ultrasonic sensor so as to transmit ultrasonic waves from the upstream ultrasonic sensor or the downstream ultrasonic sensor;
Transmission interval changing means for changing the transmission interval of ultrasonic waves transmitted from the upstream ultrasonic sensor or the downstream ultrasonic sensor;
Based on the time difference between the ultrasonic reception signals output from the upstream ultrasonic sensor and the downstream ultrasonic sensor, flow rate measuring means for measuring the flow rate of the fluid flowing in the flow path of the flow meter body,
In an ultrasonic flowmeter having
The transmission interval changing means outputs the drive signal output time by the transmitter driving means so that the transmission intervals of the upstream ultrasonic sensor and the downstream ultrasonic sensor become short when the set pressure change timing is reached. The ultrasonic wave is characterized in that the output time interval of the drive signal by the transmitter driving means is changed so that the transmission interval of the upstream ultrasonic sensor is increased when the interval is changed and the set pressure is stable. Flowmeter.   The transmission interval changing means is based on a change in the valve opening of the control valve, so that the transmission interval of the upstream ultrasonic sensor and the downstream ultrasonic sensor is shorter than a reference time interval. 2. The ultrasonic flowmeter according to claim 1, wherein an output time interval of the drive signal is changed.   The transmission interval changing means is configured to reduce the transmission intervals of the upstream ultrasonic sensor and the downstream ultrasonic sensor in a stepwise manner according to the magnitude of pressure fluctuation due to the change in the valve opening of the control valve. 2. The ultrasonic flowmeter according to claim 1, wherein an output time interval of the drive signal by the transmitter driving means is changed.

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