JPH0712625A - Small-volume proover - Google Patents

Abstract

PURPOSE:To test a flowmeter, which transmits unequal-speed pulses periodically, and highly accurately at a low cost. CONSTITUTION:The movement of a piston 8 in a measuring cylinder 3, which determines a reference volume and has a specified internal diameter, is selected so that the volume is the integer times of the theoritical discharging amount of a flowmeter, which transmits unequal-speed pulses periodically. A start mark 21 and volume marks 22-27 at an interval, which is determined for every flowmeter to be inspected having the different discharging amount, are marked on a piston rod 9. The marks are detected with a detector 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small volume prober for testing a flow meter under test which periodically emits an irregular flow rate pulse, and more particularly, it relates to a small flow prober of a type having a different theoretical discharge amount. The present invention relates to the structure of a small volume prober that defines a reference volume corresponding to each.

[0002]

2. Description of the Related Art A calibration device for calibrating a flow meter is periodically or arbitrarily tested to obtain characteristics when newly manufactured or in use to use a flow meter with reliability. A so-called characteristic test is carried out. Broadly speaking, this characteristic test consists of a calibrator that performs a test by mounting a flowmeter under test on a fixed test device and a prober-type flowmeter test that performs a test arbitrarily by mounting the flowmeter in a fluid system. Performed by the device. As mentioned above, the louver system can perform the characteristic test of the flowmeter online.
Any characteristic test can be performed as needed. Prouvers are devices that use as a reference volume a fluid discharged by a moving body such as a piston or a sphere that moves with a fluid in a tubular body with a constant cross section and the moving body moves in a predetermined section. The characteristic test is the reading of the flow meter when the reference volume of fluid specified in the prober flows,
That is, the flow coefficient, so-called K factor, is calculated from the number of flow pulses transmitted per unit volume by detecting the number of flow pulses transmitted from the flow meter. Further, if necessary, a continuous flow characteristic curve can be obtained based on the flow coefficients of a plurality of measured flow rates.

In order to obtain the flow coefficient with high resolution, it is necessary that the number of flow pulses received per reference volume is a predetermined number or more. For example, in the case of a large stationary prober with a large reference volume, it is 10,000. More than pulse is given. On the other hand, if the reference volume is made small, the flow rate pulse more than the specified number cannot be received, but the number of clock pulses (time) transmitted while the moving body such as the piston passes through the marker in the section defining the reference volume. Just before this,
Immediately after that, it is stipulated that the flow rate count be obtained by the so-called double timing method from the relationship with the number (time) of transmission pulses transmitted from the flowmeter. Therefore, even if the number of flow rate pulses is small with respect to the reference volume, a small-sized prober (hereinafter referred to as a small volume prober: SVP) can be applied. The SVP basically has a measuring cylinder with a constant cross section that is connected in series with the flowmeter under test, and when the piston moving in the measuring cylinder moves a certain distance, the volume of the fluid that is removed is the reference volume. The reference volume is compared with the reading of the flowmeter. The reference volume is actually obtained from the moving amount of the piston. In proving, usually, the results of multiple tests are averaged,
The flow coefficient (K factor) is calculated based on the average value.

However, in the double timing method, the conditions are that the test is performed at a constant flow rate and that the flow rate pulses are transmitted at equal intervals, so that the flow rate is not constant or the rotation angle of the rotor is increased. If there is pulse unevenness in which the transmission intervals of the flow rate pulses are not constant, such as in a volumetric flow meter, in which the discharge amount and the discharge amount are not in a proportional relationship, there is an error accordingly.

FIG. 4 is a view for explaining a test operation in an example of a conventional SVP. The SVP 41 has both end faces 42b,
A coaxial measuring cylinder 43 is arranged in an outer cylinder 42 having an inflow port 46 and an outflow port 47 in the vicinity of 42b.
The annular passage 43a between the measuring cylinder 43 and the
Is sealed by a partition plate 42a on the side of the outlet 47 which is close to. The measuring cylinder 43 and the annular passage 43a are communicated with each other through the inflow side through hole 44 and the outflow side through hole 45, and the piston 48 is provided in the measuring cylinder 43 between the inflow side through hole 44 and the outflow side through hole 45. Slides, and the piston rod 49 is inserted into the first actuator 50.

A position mark 60, a start mark 61 and a volume mark 6 are provided on the piston rod 49.
2 is engraved, and these marks are detected by the detector 59. On the other hand, the inflow side through hole 44 is formed by the second actuator 5
It is opened and closed by a slide valve 55 driven in the axial direction via a piston 53 and a piston rod 54 at 2. It should be noted that the slide valve 55 is configured such that a plurality of conduction paths 56 penetrates in the axial direction and can move in the measuring cylinder 43. The conventional SVP shown in FIG.
Of the measuring cylinder 4 between the start mark 61 and the volume mark 62, which are detected by the detector 59 and are moved.
The volume of 3 is the reference volume.

First, the flow meter to be tested (not shown) is provided with an inlet 4
6, the slide valve 55 is connected to the inflow side through hole 44.
And the piston rod 49 is connected to the first actuator 5
The running oil pressure is applied from the first pressure guide port 51 of 0, and the piston 48 moves to the position mark 6 of the piston rod 49.
0 is locked at the position detected by the detector 59.
The flow of the measurement fluid in this state is the flowmeter to be measured and the inlet 4
6, conducting circuit 56, inflow side through hole 44, annular passage 43a
Through the outlet 47. Next, at the start of measurement, the slide valve 55 closes the inflow side through hole 44 by introducing hydraulic pressure into the second pressure guide hole 57 of the second actuator 52, and at the same time releases the hydraulic pressure from the first pressure guide port 51. 1 Unlock the piston 48 by the actuator 50. As a result, the piston 48 moves by the fluid pressure, and the detector 59 moves from the start mark 61 to the volume mark 62.
To detect. Since the volume of fluid removed by the piston 48 during this period is a reference volume known in advance, this reference volume is compared with the measured flowmeter reading.

However, in this system, when the flowmeter to be tested is a volumetric flowmeter of the type in which the rotational angular velocity of the rotor changes even when the flow rate is constant, such as a non-circular tooth flowmeter or a roots flowmeter. Generally, since the phase of the rotor at the start mark 61 is different from the phase at the time when the volume mark 62 is reached, a flow rate difference corresponding to the phase difference occurs. The same error occurs when the theoretical flow rate of the flow meter to be measured is different. As an SVP that can eliminate the test error of the flowmeter under test that emits the irregular flow rate pulse as described above,
The start mark 61 and the volume mark 62 are eliminated, and the counter is opened and closed by using the flow rate pulse transmitted when the rotor reaches a predetermined phase at the time of start and stop as the gate signal to open and close the piston 48. It has been attempted to count a pulse signal proportional to the distance traveled by the counter.

However, in the SVP of this system, a position pulse for detecting the piston position in the start range and the stop range is defined by defining a start range and a stop range in a long section reaching the start mark and the volume mark. A transmitter is installed. The oscillator for transmitting a highly accurate position pulse having a uniform high resolution in the moving direction of the piston 48 has a divided measurement range and is applied to the double timing method even if highly accurate position detection is possible. It is very expensive to have a resolution corresponding to the clock. Moreover, the position pulse does not always represent the reference volume, because it is not the measurement by the legally recognized double timing method.

[0010]

The present invention has been made in view of the above situation, and has a rotor that rotates at a non-constant speed during the discharge of a theoretical discharge volume, and this periodically irregular flow rate pulse. The present invention has been made for the purpose of providing a high-performance and inexpensive SVP that constantly calibrates a flowmeter to be measured which transmits the signal based on a reference volume corresponding to the same rotor phase.

[0011]

In order to achieve the above object, the present invention is a flow meter which discharges a theoretical discharge amount of fluid for each rotation of a rotor and transmits an irregular flow pulse having a cycle corresponding to the rotation angle of the rotor. In the small volume prober for testing as a flow meter to be measured, the theoretical discharge amount of the flow meter to be measured is different from that of a cylinder having a constant cross section, a piston that slides liquid-tight in the cylinder due to fluid pressure It has a detector for detecting the movement amount of the piston, which has a predetermined reference volume corresponding to the theoretical discharge amount which is an integral multiple of. Hereinafter, description will be given based on examples of the present invention.

FIG. 1 is a block diagram for explaining an example of a small volume prober according to the present invention.
Is a small volume prober (SVP), 2 is an outer cylinder,
3 is a measuring cylinder, 4 is an inflow side through hole, 5 is an outflow side through hole,
6 is an inflow port, 7 is an outflow port, 8 is a piston, 9 is a piston rod, 10 is a first actuator, 11 is a first pressure guide port, 12 is a second actuator, 13 is a piston, 14
Is a piston rod, 15 is a slide valve, 16 is a passage,
Reference numerals 17 and 18 are second pressure guide ports, 19 is a detector, 20 is a position mark, 21 is a start mark, and 22 to 27 are volume marks.

In FIG. 1, the SVP 1 has both end faces 2b, 2
A coaxial measuring cylinder 3 is arranged in an outer cylinder 2 having an inflow port 6 and an outflow port 7 in the vicinity of b, and an annular path 3a between the outer cylinder 2 and the measuring cylinder 3 is a flow path close to the inflow port 46. The outlet 7 side is sealed by the partition plate 2a. The measuring cylinder 3 and the annular passage 3a are communicated with each other through the inflow side through hole 4 and the outflow side through hole 5, and the piston 8 is provided in the measuring cylinder 3 between the inflow side through hole 4 and the outflow side through hole 5. Slides and the piston rod 9 is inserted into the first actuator 10. Position mark 20 and start mark 2 on piston rod 9.
1 and volume marks 22 to 27 corresponding to an integral multiple of the theoretical discharge amount of the flowmeter to be measured and a volume mark 28 irrelevant to the theoretical discharge amount are provided, and these marks are detected by the detector 9. On the other hand, the inflow side through hole 4 is opened / closed by a piston 13 of the second actuator 12 and a slide valve 15 axially driven via a piston rod 14. It should be noted that the slide valve 15 is configured such that a plurality of communication passages 16 penetrate in the axial direction so that the slide valve 15 can move in the measuring cylinder 3.

The SVP shown in FIG.
The volume of the measuring cylinder 3 between the start mark 21 and the volume marks 22 to 28 detected by the detector 19 becomes the reference volume. Initially, the flow meter to be measured (not shown) is connected to the inflow port 6, and the slide valve 15
Opens the inflow side through hole 4, and the piston 8 is locked at a position where the piston rod 9 position mark 20 is detected by the detector 19. At this time, the running hydraulic pressure is applied to the piston rod 9 from the first pressure guide port 11 of the first actuator 10. The flow of the measurement fluid in this state flows out of the outflow port 7 through the flowmeter to be measured, the inflow port 6, the conducting path 16 and the annular path 3a.

Next, at the start of measurement, the slide valve 15 closes the inflow side through hole 4 by introducing hydraulic pressure into the second pressure guide hole 17, and at the same time releases the pressure applied to the first pressure guide port.
The engagement of the piston 8 by the first actuator 10 is released. As a result, the piston 8 is moved by the fluid, and the detector 19 detects any of the volume marks 22 to 27 corresponding to the flow meter to be measured from the start mark 21. If the flowmeter to be tested is a flowmeter that transmits flow pulses at equal intervals, such as a turbine meter, the volume mark 2
8 is selected. However, even if it is not the volume mark 28, if the required reproducibility is obtained, the volume mark 22 that can obtain the minimum reference volume may be selected, and the number of steps can be greatly reduced. Since the volume of fluid removed by the piston 8 during this period is a reference volume known in advance, this reference volume is compared with the reading of the flowmeter to be measured.

FIG. 2 is a diagram for explaining an application example of the small volume prober according to the present invention, in which 30 is a flowmeter to be measured, 31 is a pulsar, 32 is a reduction gear, 33 is a register, and 34 is proving. A counter, 35 is a flow path,
Parts having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

In the figure, SVP1 is the same as that in FIG. 1 and its explanation is omitted. The measured flow meter 30 is, for example, a non-circular gear flow meter, and a pair of meshing non-circular rotors (not shown) rotate. Under the condition that the flow rate is constant, the rotor rotates at a rotation angular velocity with a constant elliptical area velocity. The pulsar (pulse generator) 31 outputs a flow rate pulse that is unequal in speed in proportion to the rotational angular velocity. The reduction gear 32 is a conversion gear that has a gear train of a large number of stages, and decelerates the rotation of the rotor to perform correction rotation so as to obtain a decimal amount such as one rotation, one liter, and ten liters.
Outputs a unit pulse of 1 liter, 10 liter, or the like. The proving counter 34 includes the start mark 21 and the volume mark 22 detected by the detector 9.
It is an integrator that inputs a non-uniform velocity pulse from the pulsar 31 or a unit pulse from the register 33 into a reference volume defined between the unit 27 and the unit and calculates it.

In the embodiment connected as shown in FIG. 2, the valve V ₂
Is closed and the other valves V ₁ and V ₃ are opened to allow the fluid to flow out to the SVP 1 through the measured flowmeter 30. If the start command is input and the piston 8 moves, and the detector 9 detects the start mark 21 and the volume mark corresponding to the flowmeter 30 to be detected, for example, the volume mark 22, the pulser 31 transmits a pulse having a cycle. The constant-velocity flow pulse is a non-constant-rate flow pulse having the same phase at the start mark 21 and the volume mark 22. In the case of the measured flowmeters corresponding to the other volume marks 23 to 27, the phases are similarly the same.

FIGS. 3 (a), (b), (c) and (d) are pulse trains for explaining how to obtain the K factor (flow coefficient) by the small volume prober according to the present invention. FIG. 3 (b) is a non-uniform flow rate pulse train having a non-uniform velocity periodically output from the pulser 31, FIG. 3 (a) is a constant-speed pulse train having a pulse number equal to the pulse number of the non-uniform velocity pulse train, and FIG. 3C is a curve showing an example of the rotational angular velocity of the rotor, and FIG. 3D is a pulse train corresponding to FIG. 3B. When the rotor of the flowmeter 30 to be tested is rotating at a non-uniform speed as shown in FIG. 3C, the flow rate pulse output from the pulsar 31 is as shown in FIGS. 3B and 3D. The pulse interval is large when the rotational angular velocity is large, and the pulse interval is small when the rotational angular velocity is small. Start mark 21
The start signal of the detector 9 when passing through Ps,
Stop signal P indicating that the volume mark 22 has been passed
Assuming t, the start signal Ps and the stop signal Pt have the same phase. This period is T ₂ , and the emission amount is D.
Further, N _A is an integer of non-uniform velocity pulses output between the start signal Ps and the stop signal Pt, and an integer N of constant-velocity pulses equal to the number of pulses in the period of the non-uniform velocity pulses.
t, the time from the non-uniform velocity pulse 1 from which the start signal Ps is transmitted to the N _{A + 1 non-} uniform velocity pulse output immediately after the stop signal Pt is T _1A. Assuming that the time from the fast pulse 1 to the constant velocity pulse Nt is T ₁ t, the interpolation pulse Nt ′ of the constant velocity pulse is

[0020]

[Equation 1]

Since N _A = Nt and T _1A = T ₁ t, the interpolation pulse N ′ _A of the non-uniform velocity pulse is

[0022]

[Equation 2]

Therefore, the number of interpolation pulses for non-uniform velocity pulses becomes equal to the number of interpolation pulses for constant velocity pulses. Therefore, the K factor is

[0024]

[Equation 3]

According to the above, the K factor can be obtained as in the case of the flowmeter to be measured which emits the constant velocity flow pulse. In short, in the SVP of the present invention, by engraving the volume mark so that the reference volume is equal to an integral multiple of the theoretical discharge amount of the flow meter to be measured which periodically emits the non-uniform flow rate pulse, the target volume of each pass is measured. Make the number of pulses of the flowmeter the same, that is, treat a periodically nonuniform pulse train as a uniform pulse train with the same number of pulses, and apply the pulse interpolation method as it is to each path corresponding to the reference volume. The repeatability of measuring the pulse number of the measured flowmeter up to a fraction is improved.

In the above description, the reference volume is defined as one detector 19, the start mark 21 detected by the detector 19, and the volume of the measuring cylinder 3 when the piston 8 moves between the plurality of volume marks 22 to 27. Although defined, one reference mark is formed on the piston rod 9, and the reference mark is detected by a plurality of detectors arranged at positions corresponding to the start mark 21 and the volume marks 22 to 27. The volume may be defined.

By providing a reference amount equal to an integral multiple of the periodic theoretical measured amount of the measuring meter to be measured, which periodically transmits a pulse train of inconstant measured amount, the period to be transmitted by the measured instrument is measured. The non-uniform flow pulse train is treated as a uniform measured amount pulse train having the same number of pulses periodically, and the flow pulse number transmitted by the measured flow meter corresponding to the reference amount by the pulse interpolation method is increased up to a fraction. The present invention can also be diverted to the efficient verification of a measuring instrument such as the length, displacement amount, level, and rotation amount of the present invention which is measured by the ability.

[0028]

As is apparent from the above description, according to the small volume prober of the present invention, the test flow meter that periodically transmits the non-uniform velocity flow pulse is an integer of the theoretical discharge amount of the test flow meter. Since the doubled volume is selected as the reference volume, no special detector is required and the same flowmeter test as the flowmeter under test for constant velocity flow pulse can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an example of a small volume prober according to the present invention.

FIG. 2 is a diagram for explaining another embodiment of the small volume prober according to the present invention.

FIG. 3 is a diagram showing a pulse train for explaining a method of obtaining a K factor flow coefficient by the small volume prober according to the present invention.

FIG. 4 is a diagram for explaining a conventional SVP test operation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Small volume prober (SVP), 2 ... Outer cylinder, 3 ... Measuring cylinder, 4 ... Inflow side through hole, 5 ... Outflow side through hole, 6 ... Inflow port, 7 ... Outflow port, 8 ... Piston, 9 ... Piston rod, 10 ... 1st actuator, 11 ... 1st
Pressure guide port, 12 ... Second actuator, 13 ... Piston, 14 ... Piston rod, 15 ... Slide valve, 16 ...
Conduction path, 17, 18 ... Second pressure port, 19 ... Detector,
20 ... Position mark, 21 ... Start mark, 22
~ 27 ... Volume mark, 30 ... Flow meter under test, 31 ...
Pulser, 32 ... Reduction gear, 33 ... Register, 34 ... Proving counter, 34 ... Flow path.

Claims (1)

[Claims] 1. A small volume for testing, as a test flow meter, a flow meter which discharges a theoretical discharge amount of fluid for each rotation of a rotor and transmits an irregular flow pulse having a cycle corresponding to a rotation angle of the rotor. In the louver, the number of theoretical discharges is an integer multiple of the theoretical discharge of the cylinder with a constant cross section, the piston that fluid-tightly slides inside the cylinder due to fluid pressure, and the theoretical flow of each different theoretical discharge. A small volume prober having a detector for detecting the amount of movement of the piston whose reference volume is predetermined.