JPH08201147A - Flow rate corrector for flowmeter - Google Patents

Abstract

PURPOSE: To eliminate a complicated mechanical correcting process and to obtain an instantaneous flow rate with high accuracy. CONSTITUTION: A disc 51 is rotated at a speed responsive the a gas flow rate, a pulse at each one revolution of the disc 51 is generated by a waveform shaper 57, and a pulse of a period responsive to the flow rate is generated by a waveform shaper 59. A flow rate corrector measures the period of the pulse output from the shaper 59 by a pulse period measuring unit 61, and fiber positions during one period of the rotation of the disc 51 are decided by a position detector 62. A correction factor calculator 61 calculates a correction factor responsive to the decided position by the flow rate and the detector 62, and a flow rate calculator 65 calculates the corrected flow rate based on the pulse period measured by the unit 61 and the factor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate correction device for a flow meter that corrects instrumental differences that differ depending on the flow rate.

[0002]

2. Description of the Related Art Generally, in a flow meter used for a gas meter or the like, if the flow rate (flow velocity) passing therethrough is different, the instrumental difference is different. Here, the instrumental error refers to the difference between the indicated flow rate of the reference instrument and the indicated flow rate of each flow meter, expressed as a percentage of the indicated flow rate of each flow meter. Further, in the flowmeter, a measurement error due to the mechanism also occurs depending on the fluid passage amount during the test. Therefore, for gas meters, conduct a test with the flow rate (verification flow rate) and passage rate according to the maximum usable flow rate or number indicated on the gas meter, and correct the gas meter so that the instrumental error is within the verification tolerance. It is defined by the Measurement Law.

FIG. 6 is a characteristic diagram showing a test tolerance. As shown by the diagonal lines in this figure, the test tolerance is 2.5% for the flow rate of 1/20 or more and less than 1/5 of the maximum flow rate, and 1. for the flow rate of 1/5 or more and less than 4/5 of the maximum flow rate. 5
%, And 2.5% for a flow rate of 4/5 or more of the maximum flow rate.

Therefore, conventionally, the instrumental difference is measured at two points of the maximum flow rate and the verification flow rate (about 30% of the maximum flow rate), and the number of teeth and the rotation timing of the gear in the mechanical movable part that moves according to the flow rate are measured. The gas meter was manufactured by making mechanical corrections such as changing.

[0005]

However, the above-described correction method requires a step of performing a complicated mechanical correction process such as gear replacement for correcting the instrumental error on the manufacturing line, and thus the gas meter. In addition to the increase in cost, there is a risk that defective products may be generated due to incorrect operation.

Further, as a method for measuring the flow rate in a gas meter having a mechanically movable portion such as a membrane gas meter, one cycle of the operation of the mechanically movable portion is disclosed, for example, as disclosed in JP-A-5-107096. A disk that makes one rotation in conjunction with the disk is provided, and a plurality of magnets provided on the disk and a magnetoresistive element provided in the vicinity of the disk are used during one cycle of the operation of the mechanical movable part. To output multiple pulses,
There is a method of calculating the flow rate from the frequency and period of this pulse.

However, in a membrane gas meter or the like, even when the flow rate is constant, the speed of the disc that is interlocked with the mechanically movable portion changes depending on the rotational position during one rotation, for mechanical reasons. There is a case. Furthermore, the mode of speed change of the disc may change depending on the flow rate. In such a case, there is a problem that the pulse period changes even if the flow rate is constant, and an error occurs in the measured instantaneous flow rate.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a flowmeter capable of obtaining a highly accurate instantaneous flow rate while eliminating the need for complicated mechanical correction processing. It is to provide a flow rate correction device.

[0009]

According to a first aspect of the present invention, there is provided a flow rate correction device for a flow meter, which corrects a measured flow rate in a flow meter having a mechanically movable portion that periodically operates at a speed according to the flow rate. A flow rate correction device for a flow meter, which detects a plurality of positions in one cycle of the operation of a mechanical movable portion and outputs a pulse corresponding to each position, and a position detection means for detecting the position. Pulse period measuring means for measuring the period of the output pulse, and correction information determined according to the flow rate corresponding to the pulse period measured by the pulse period measuring means and a plurality of positions detected by the position detecting means. A correction table that stores, and by referring to this correction table, the flow rate corresponding to the pulse period measured by the pulse period measuring means and the position detected by the position detecting means. Obtains correction information corresponding, on the basis of the measured pulse period by the correction information and the pulse period measuring means, in which a correction flow rate calculating means for calculating a corrected flow rate.

In the flow rate correction device of this flow meter, the position detecting means detects a plurality of positions in one cycle of the operation of the mechanical movable portion, and the position detecting means outputs a pulse corresponding to each position. It is output and the period of this pulse is measured by the pulse period measuring means. Then, the correction flow rate calculation unit refers to the correction table, obtains correction information according to the flow rate corresponding to the pulse period and the position detected by the position detection unit, and based on this correction information and the pulse period, The corrected flow rate is calculated.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 to 5 relate to an embodiment of the present invention.

FIG. 1 is a sectional view showing a schematic structure of a membrane gas meter as a flow meter including the flow rate correcting device of this embodiment. As shown in this figure, the gas meter has a case main body 10, and a gas inlet portion 1 is provided at an upper portion of the case main body 10.
1 and a gas outlet 12 are provided. A front weighing chamber 20 and a rear weighing chamber 30 are provided inside the case body 10.

A membrane 21 is provided in the center of the front side measuring chamber 20 in the front-back direction (the left side in the drawing is the front side), and a membrane plate 22 is attached to the membrane 21. Here, the space in front of the membrane 21 in the front measuring chamber 20 is defined as a chamber, and the space in the rear is defined as a chamber. A gas inlet / outlet portion 23 that communicates with the chamber and a gas inlet / outlet portion 24 that communicates with the chamber are provided at the upper portion of the front measuring chamber 20. A blade shaft 26 is connected to the membrane plate 22 via a blade 25. The blade shaft 26 is adapted to rotate as the membrane 21 moves in the front-rear direction. Further, the blade shaft 26 is used for the front measuring chamber 2
It penetrates 0 and projects to the upper part.

Similarly, in the rear measuring chamber 30, a film 31 is provided at the center in the front-rear direction, and a film plate 32 is provided on the film 31.
Is attached. Here, the space in front of the membrane 31 in the rear measurement chamber 30 is defined as a chamber, and the space in the rear is defined as a chamber. A gas inlet / outlet portion 33 that communicates with the chamber and a gas inlet / outlet portion 34 that communicates with the chamber are provided on the upper portion of the rear measuring chamber 30. A blade shaft 36 is connected to the film plate 32 via a blade. The blade shaft 36 is adapted to rotate as the film 31 moves in the front-rear direction. Further, the blade shaft 36 penetrates the rear measuring chamber 30 and projects upward.

Further, between the gas inlet / outlet portions 23 and 24,
An opening of the gas outlet pipe 13 is arranged between the gas inlet / outlet portions 33 and 34. This gas outlet pipe 13
Is connected to the gas outlet 12. A valve 14 is provided above the gas inlet / outlet portions 23 and 24. The valve 14 has a state in which both the gas inlet / outlet portions 23 and 24 are closed, and the gas inlet / outlet portion 23 and the gas outlet pipe 13 are
It is possible to select a state in which the gas outlet port 24 and the gas outlet pipe 13 are in communication with each other. Similarly, the valve 15 is provided above the gas inlet / outlet portions 33 and 34. The valve 15 has a state in which the gas inlet / outlet portions 33 and 34 are both closed, a state in which the gas inlet / outlet portion 33 and the gas outlet pipe 13 are in communication, and a state in which the gas inlet / outlet portion 34 and the gas outlet pipe 13 are in communication. You can choose.

An elbow 27 is connected to the upper end of the blade shaft 26, and an elbow 37 is connected to the upper end of the blade shaft 36. These elbows 27 and 37 are connected to the adjusting plate 42 by pins 41. A crank arm 44 and valve arms 45 and 46 are connected to the adjusting plate 42 via a crank pin 43. The crank arm 44 is connected to a crank shaft 47 and is configured to rotate the crank shaft 47. Also, the valve arms 45, 4
6 is connected to the valves 14 and 15, respectively, and moves the valves 14 and 15. A disc, which will be described later, is attached to the crankshaft 47 via a worm and a worm wheel (not shown).

An outline of the operation of the gas meter shown in FIG. 1 will be described with reference to FIG. Weighing room 20,
The introduction of gas into 30 and the discharge of gas from the measuring chambers 20 and 30 are performed by the interlocking action of the valves 14 and 15 and the membranes 21 and 31. The driving force of the movement of the membranes 21 and 31 is the pressure difference between the gas at the gas inlet 11 and the gas outlet 12. In the state shown in FIG. 2A, the valve 14 closes both the gas inlet / outlet portions 23 and 24, and the valve 15 connects the gas inlet / outlet portion 33 and the gas outlet pipe 13. In this state, the gas entering the chamber through the gas inlet / outlet portion 34 pushes the membrane 31 toward the chamber due to the pressure difference, and the gas in the chamber passes through the gas inlet / outlet portion 33, the valve 15 and the outlet pipe 13 in this order, and the gas outlet portion. It is discharged from 12. The movement of the membrane 31 is transmitted in the order of the blade shaft 36, the elbow 37, the adjusting plate 42, and the valve arms 45 and 46, and as shown in FIG. 2B, the valve 14 is moved to the gas inlet / outlet portion 24 and the gas outlet pipe. 1
The valve 15 is moved to a state where it communicates with the valve 3, and the valve 15 is moved to a state where both the gas inlet / outlet portions 33 and 34 are closed. At this time, the gas in the room is the gas inlet / outlet part 23 and the valve 1.
4, the gas passes through the outlet pipe 13 in order and is discharged from the gas outlet 12. Thereafter, similarly, the motion of returning to the state of (a) through the states of FIGS. 2 (c) and (d) is repeated. Further, the crank arm 44 and the crank shaft 47 rotate due to the above movement. Then, the rotation of the crank shaft 47 rotates a disc described later through a worm and a worm wheel (not shown).

FIG. 3 is a block diagram showing the circuit configuration of a gas meter including the flow rate correction device of this embodiment. In this figure, reference numeral 51 is a disk connected to the crankshaft 47 as described above. The disc 51 is adapted to make one rotation corresponding to one cycle of the operation of the gas meter shown in FIG. This disc 51 has one magnet 5 near the outer periphery.
2 are attached, and at a position inside the magnet 52, a plurality of, for example, 5 are provided at equal intervals along the circumferential direction.
Two magnets 53 are attached. The gas meter further includes a magnetoresistive element 54 provided at a position facing the magnet 52 and a magnetoresistive element 55 provided at a position facing the magnet 53. These magnetoresistive elements 5
Reference numerals 4 and 55 detect changes in the magnetic field due to the approach and separation of the magnets 52 and 53 as changes in the resistivity. The gas meter further includes an analog amplifier 56 for amplifying the output signal of the magnetoresistive element 54 and a waveform shaping circuit 57 for shaping the output signal of the analog amplifier 56 to generate a pulse.
An analog amplifier 58 for amplifying the output signal of the magnetoresistive element 55, and a waveform shaping circuit 59 for shaping the output signal of the analog amplifier 58 to generate a pulse.

The gas meter further includes a pulse period measuring section 61 for measuring the period of the pulse output from the waveform shaping circuit 59, a pulse output from the waveform shaping circuit 57 and a pulse output from the waveform shaping circuit 59. Based on this, a position determination unit 62 that determines the positions of five locations in one cycle of rotation of the disk 51, and a flow rate and a position determination unit 63 that correspond to the pulse period measured by the pulse period measurement unit 61 are determined. A correction table 63 that stores a correction coefficient determined according to the position, and a correction coefficient calculation that refers to the correction table 63 and calculates a correction coefficient according to the flow rate and the position determined by the position determination unit 62. Part 64,
A flow rate calculation unit 65 that calculates a corrected flow rate and an integrated flow rate based on the correction coefficient calculated by the correction coefficient calculation unit 64 and the pulse period measured by the pulse period measurement unit 61, and the flow rate calculation unit 65. And a display unit 66 for displaying the integrated flow rate obtained by. Pulse period measurement unit 61, position determination unit 62, correction table 6
3, the correction coefficient calculation unit 64 and the flow rate calculation unit 65 are realized by, for example, the microcomputer 60.

FIG. 4 shows an example of the contents of the correction table 63. (A) has an average flow rate of 500 l / h
Table contents when less than, (b) average flow rate is 50
The contents of the table are shown when the value is 0 liter / h or more and less than 1000 liter / h. Although not shown,
Similar tables are prepared for the average flow rate of 1000 liters / h or more according to the appropriately divided flow rate range. As shown in FIG. 4, the correction table 63 stores a correction coefficient determined according to the average flow rate and the position determined by the position determination unit 63.

The flow rate calculation unit 65 calculates the corrected flow rate Q based on the correction coefficient calculated by the correction coefficient calculation unit 64 and the pulse period measured by the pulse period measurement unit 61, for example, by the following equation. Calculate However, T is a pulse period and k is a correction coefficient.

[0022]

## EQU1 ## Q = k / T

The flow rate calculator 65 calculates an average flow rate for each predetermined time from the calculated flow rate, and switches the contents of the correction table 63 according to the average flow rate. For example, when the average flow rate is less than 500 liters / hour, FIG.
When the average flow rate changes from 500 liters / h or more to less than 1000 liters / h, the table having the content shown in FIG. 4B is switched to be used. .

The contents of the correction table 63 are set in advance.
Based on the flow rate indicated by the gas meter before correction and the flow rate indicated by the reference device, the corrected flow rate is set to match the reference flow amount indicated by the reference device.

Next, the operation of the flow rate correction device of this embodiment will be described with reference to the flow chart of FIG. The gas meter performs the operation shown in FIG. 2 at a speed according to the gas flow rate, and with this operation, the disk 51 shown in FIG. 3 rotates at a speed according to the gas flow rate. Then, the magnet 5 provided on the disk 51
The output of the magnetoresistive element 54 changes with the approach and separation of 2, the output signal of the magnetoresistive element 54 is amplified by the analog amplifier 56, and the waveform is shaped by the waveform shaping circuit 57.
Every one rotation of the disk 51, that is, one operation of the gas meter
A pulse for each cycle is generated. On the other hand, the output of the magnetoresistive element 55 changes with the approach and separation of the five magnets 53 provided on the disk 51, and the output signal of the magnetoresistive element 55 is amplified by the analog amplifier 58 and the waveform shaping circuit 59. The waveform is shaped by, and a pulse having a period according to the flow rate is generated. As shown in FIG. 5, the flow rate correction device first measures the period of the pulse output from the waveform shaping circuit 59 by the pulse period measuring unit 61 (step S101). Next, based on the pulse output from the waveform shaping circuit 57 and the pulse output from the waveform shaping circuit 59, the position detection unit 62 outputs 5 pulses in one cycle of rotation of the disk 51.
The position of the place is determined (step S102). Next, the correction coefficient calculation unit 64 calculates a correction coefficient according to the flow rate and the position determined by the position determination unit 62 (step S103). Next, the flow rate calculation unit 65 calculates the corrected flow rate based on the pulse period measured by the pulse period measurement unit 61 and the correction coefficient calculated by the correction coefficient calculation unit 64 (step S10).
4). Then, the integrated flow rate obtained by integrating the corrected flow rates is displayed on the display unit 66. In addition, the flow rate calculation unit 6
5, the contents of the correction table 63 are switched according to the average flow rate.

As described above, according to this embodiment, a plurality of positions in one cycle of the operation of the mechanically movable portion of the gas meter are detected, and the correction table 63 is referred to determine the average flow rate and the corresponding positions. Since the correction coefficient is obtained and the corrected flow rate is calculated based on the correction coefficient and the pulse period, a complicated mechanical operation such as gear replacement for correcting the instrumental error is performed on the manufacturing line. The process of performing the correction process is not required, the cost of the gas meter can be reduced, and the defective product due to an erroneous operation can be prevented, so that the process management is simplified.

In this embodiment, since the flow rate is corrected by referring to the correction table 63, the flow rate can be easily corrected regardless of the relationship between the flow rate before correction and the correct flow rate. A more accurate correction is possible as compared with a mechanical correction.

Further, in this embodiment, since the correction is performed according to the position and the average flow rate of the mechanically movable portion of the gas meter during one cycle, the mechanically movable portion operates at the position within one cycle. It is possible to obtain a highly accurate instantaneous flow rate even when it changes according to

The present invention is not limited to the above embodiments, and the correction table 63 may store a correction coefficient corresponding to the pulse period and the position determined by the position determination unit 62, for example. In this case, the correction coefficient calculation unit 64 uses the pulse cycle measured by the pulse cycle measurement unit 61 and the position determined by the position determination unit 62 to obtain the correction coefficient from the correction table 63.

As the position detecting means, a magnet 52,
Instead of 53 and the magnetic resistance elements 54 and 55, an optical rotary encoder or the like may be used. Further, the position detecting means may detect the position of the mechanically movable portion that periodically reciprocates in the gas meter at a speed according to the flow rate.

The flow rate correction device for a flow meter according to the present invention is
The present invention can be applied not only to the membrane gas meter but also to other types of gas meters having mechanically movable parts.

[0032]

As described above, according to the flow rate correction device of the flow meter of the present invention, the position detection means detects a plurality of positions in one cycle of the operation of the mechanical movable portion, and the position detection means. The pulse period measuring means measures the period of the pulse output from the pulse period, the correction flow rate calculating means refers to the correction table, and the correction information according to the flow rate corresponding to the pulse period and the position detected by the position detecting means. Then, the corrected flow rate is calculated based on the correction information and the pulse period, so that a complicated mechanical correction process is unnecessary and a highly accurate instantaneous flow rate can be obtained. There is an effect.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a gas meter including a flow rate correction device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an outline of the operation of the gas meter shown in FIG.

FIG. 3 is a block diagram showing a circuit configuration of a gas meter including a flow rate correction device according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an example of contents of a correction table in FIG.

FIG. 5 is a flowchart showing an operation of the flow rate correction device according to the embodiment of the present invention.

FIG. 6 is a characteristic diagram showing a test tolerance.

[Explanation of symbols]

 51 disk 52, 53 magnet 54, 55 magnetoresistive element 57, 58 waveform shaping circuit 61 pulse period measuring unit 62 position determining unit 63 correction table 64 correction coefficient calculating unit 65 flow rate calculating unit

Claims (1)

[Claims] 1. A flowmeter having a mechanically movable part that periodically operates at a speed according to the flowrate, which is a flowmeter correction device for a flowmeter that corrects the measured flowrate. Position detecting means for detecting a plurality of positions in one cycle of operation and outputting a pulse corresponding to each position; pulse cycle measuring means for measuring a cycle of a pulse output from the position detecting means; A correction table storing correction information determined according to the flow rate corresponding to the pulse period measured by the pulse period measuring unit and a plurality of positions detected by the position detecting unit, and with reference to this correction table, The correction information corresponding to the flow rate corresponding to the pulse period measured by the pulse period measuring unit and the position detected by the position detecting unit is obtained, and the correction information is obtained. Said based on the pulse period measured by the pulse period measuring means, the corrected flow meter flow rate correction apparatus characterized by comprising a correction flow rate calculating means for calculating the flow rate.