JPS59226826A - Flow rate measuring device - Google Patents

Abstract

PURPOSE:To take an accurate measurement by calculating a flow rate from the mean value of stored time intervals when a measured time interval is shorter than a specific value or from the mean value of the measured time interval when longer. CONSTITUTION:A reed switch 3 transmits a flow rate pulse every time a meterz measures unit measurement volume. Time intervals of flow rate pulses are measured by a timer 5, whose measurement results are inputted to an arithmetic processing part 6 to calculate the flow rate per unit time. When the flow-rate pulse interval is shorter than the specific time, the mean of a specific number of the past measurement results is calculated and the flow rate per unit time is calculated from the mean value. When the flow rate pulse interval is longer than the specific time, the flow rate per unit time is calculated from the current measured time interval or the mean value of the current and last measured time intervals. Consequently, the flow-rate pulses synchronize with the measurement time completely, so the flow rate per unit time is measured accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow rate measuring device suitable for measuring the flow rate of a fluid, and more particularly to a flow rate measuring device intended to measure the flow rate per unit time.

2. Description of the Related Art Structures of Conventional Examples and Their Problems Conventional gas flow devices include, for example, so-called model gas meters. This gas meter includes, for example, four measuring chambers partitioned by two membranes, a link mechanism that transmits movement of the membranes, a valve driven via the link mechanism,
It consists of an instruction section. Each time the membrane moves back and forth, a unit measurement volume determined for each gas meter size is measured. The measured value of the gas meter is displayed on the indicator, but as is well known, this indicator indicates the integrated value of the amount of gas passing through the meter, and does not indicate the flow rate per unit time.

A flow sensor consists of a disk with a permanent magnet attached to a part of its circumference on the rotating shaft of the gas meter, and a Hall IC that detects the magnetic field of the permanent magnet, and the flow rate pulse from this flow rate sensor is counted every minute. Devices are known that calculate the average flow rate of . Since such devices count the number of pulses within a predetermined measurement time, the flow rate pulse is input at the start of measurement, the flow pulse is input at the end of measurement, and so on. If the flow rate pulses are synchronized, the average flow rate can be calculated accurately, but if they are asynchronous, that is, the measurement start or end point is different from the flow rate pulse input point, the calculation becomes inaccurate. Generally, even if the measurement start point and the flow rate pulse are synchronized, they are asynchronous at the end point. Therefore, with this device, there is no accuracy of the average flow rate over the entire range of measured flow rates. Furthermore, it is not possible to measure low flow rates where the time interval between flow rate pulses is longer than a predetermined measurement time, for example, one minute. Furthermore, approximately the same measurement time is required for both large and small flow rates, and although it is desirable that the larger the flow rate, the shorter the measurement time, a predetermined amount of time is required even in such cases.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional problems.By measuring the time interval of flow pulses, it is possible to accurately measure the flow rate per unit time from low flow rates to large flow rates. The purpose is to measure the flow rate so that the measurement time becomes shorter as the flow rate increases.

Structure of the Invention In order to achieve the above object, the flow rate measurement device of the present invention includes a flow rate sensor that is installed in a gas supply line and that emits a flow rate pulse every time a predetermined unit measurement volume is measured, and a flow rate measurement device that measures the flow rate from the flow rate sensor. It is composed of a processing unit that calculates the flow rate per unit time based on the time interval of the pulse, and the processing unit has a timer that measures the time interval, and a processing unit that calculates the flow rate per unit time. , calculate the average time interval from the previous time interval measurement results stored in the memory and the current measurement results, calculate the flow rate per unit time from the 4-hour interval, and calculate the current measured time interval. When the time is longer than the predetermined time, the time of the flow pulse is When the interval is shorter than a predetermined time (for example, 20 seconds), the flow rate per unit time is calculated from the average value of the measurement results of a predetermined number of times (for example, 3 times), so the measurement time and flow rate pulse are completely different. It is possible to synchronize and make accurate measurements when the time interval between flow rate pulses is longer than a predetermined time, and the flow rate can be calculated from the results of one or two measurements, making it possible to perform accurate measurements in the low flow area as before. In addition, in this case, the average value of one or two measurements is calculated, so the measurement time does not become long, and the flow rate per unit time can be measured accurately in a relatively short time. This has the effect of

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 is a flow rate sensor installed in the gas supply line, a model gas meter 2, and a model gas meter 2.
A permanent magnet is provided in the membrane or link mechanism, and a reed switch 3 is used as a magnetic field detector to detect the magnetic field of the permanent magnet to detect the reciprocation of the membrane. reed switch 3
The reed switch 30 turns on and off twice each time the meter 2 measures a unit measurement volume, and this change from off to on of the reed switch 30 is transmitted as a flow rate pulse. 4 is an arithmetic processing unit, which has a timer 5 for measuring time intervals of flow rate pulses and a storage section 7 for storing past measured time intervals; and a calculation processing section 6 that calculates the flow rate per unit time from the measurement results. A typical example of the arithmetic processing section 6 is a microcomputer, and when a microcomputer having a time measurement function is used, the timer 6 can be built into the microcomputer.

The operation of the above configuration will be explained below.

When the meter 2 measures a unit metered volume, the reed switch 3 emits a flow pulse that turns from off to on. The time interval of the flow rate pulse is measured by a timer 5, and the measurement result is input to the arithmetic processing section.

The arithmetic processing unit 6 determines that the measurement time interval is a predetermined time (for example, 2
0 seconds) or less. If it is 20 seconds or less, the measurement result is multiplied by a certain coefficient α (for example, 1%) that takes into account variations in measurement time when a constant flow rate is applied. Expressed in a formula, if the measurement time is TP and the coefficient is α, then α·Tp is obtained. Next, among the past measurement results stored in the storage unit, the latest one, that is, the previous measurement result Tp
Absolute value of the difference between -1 and the current measurement result Tp 1TP-1-T
Calculate p I. Next, ΔTp-α・Tp and the above 1T
Compare with P-1-TPl, lTp≧1TP' 1-T
If it is Pl, it is assumed that there is no change, and an average value Tp is determined from a predetermined number of past measurement results stored in the storage unit and the current measurement results. For example, to obtain the measurement results from the previous measurement and the current measurement (ie, the average of the three measurements), (TP - 20 TP
-1+TP)/3-TP. Next, from the average time interval T obtained in this way and the unit metering volume Fu of the meter, the flow rate per unit time q Ire: F u /T
p, and output the result as the flow rate q. If l Tp-α·TP is 1 Tp * Tp 1, it is determined that there is a flow rate change, and it is output as a change signal qc, and all data in the storage element is erased. In this way, the sum of the number of times of the measurement result stored in the memory boundary section 7 and the current measurement result reaches a predetermined number of times (for example, 3 times).
, the previous measurement result and the current measurement result satisfy the two-way relationship (ΔTp-α・Tp≧1TP-1-TPl)
In this case, the average time interval is calculated from the measurement results stored in the storage unit 7 and the current measurement results, and the flow rate per unit time is calculated.

Next, a case in which the measured time interval is longer than a predetermined time will be explained. In this case as well, the measurement result is first multiplied by a constant coefficient β, as in the case of two series. In this case, β is the coefficient α
It may be the same as , and since it is a long measurement,
It can be a large value. Next, the previous measurement result TP-1
The absolute value of the difference between the current measurement result Tp and the previously calculated β・T
Compared to p, if β・T>1T −T 1,
This time, based on the measurement result Tp of P-P-I P and the unit measurement volume Fu, Fu/T
By calculating P, the flow rate q per unit time is output. Then β
・If TP<1TP-1-TPl, change signal qC
is output, the stored contents of the storage unit 7 are erased, and the current measurement result is stored in the storage unit 7 as the previous measurement result in preparation for the next measurement calculation. In this way, the previous measurement result Tp stored in the storage unit 7 and the current measurement result Tp are β·Tp
As mentioned above, if ≧1TP-1-TPi is satisfied, F
Calculate u/T and obtain the flow rate q per unit time. In the above example, the flow rate q was calculated from the current measurement result Tp, but the average value T of the previous measurement result Tp * and the current measurement result Tp
From p-(T + T)/Z, the flow rate P-I
P−q may also be calculated.

Next, when the time interval of the flow rate pulses is extremely long, that is, the flow rate becomes extremely low or zero, that is, when the time interval measured by the timer 5 becomes longer than the second predetermined time, The arithmetic processing unit 6 outputs the zero flow rate as q, erases all the memory contents of the storage unit, and waits for the next flow rate pulse to be stored by the timer 5.

According to this embodiment, when the flow rate pulse interval is within a predetermined time, the average of a predetermined number of past measurement results is calculated;
The flow rate per unit time is calculated from this average value, and if the flow rate pulse interval is longer than a predetermined time, the flow rate per unit time is calculated from the current measurement time interval or from the average value of the current and previous measurement time intervals. In this case, the flow rate pulse and the measurement time are completely synchronized, and the flow rate can be accurately measured per unit time without causing errors as in asynchronous measurement. It has the effect that even a low flow rate with a flow pulse interval longer than a predetermined time can be measured, and the larger the flow rate, the shorter the flow pulse time interval, and therefore the measurement time.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) The flow rate pulse and measurement time can be synchronized, allowing accurate flow rate measurement.

(2) Measurement is possible even if the time interval between flow rate pulses exceeds a predetermined time, and measurement is possible even in the low flow rate range.

(3) As the flow rate increases, the flow rate pulse interval becomes shorter and the measurement time becomes shorter.

[Brief explanation of the drawing]

The figure is a schematic configuration diagram of a flow rate measuring device according to an embodiment of the present invention. 1...Flow rate sensor, 4...Arithmetic processing unit, 5...Timer, 6...Arithmetic processing unit, 7
...Memory section.

Claims (1)

[Claims] a flow rate sensor installed in a fluid supply line and transmitting a flow rate pulse each time a unit measurement volume is measured; and a processing unit that receives the flow rate pulse as an input and calculates the flow rate per unit time from the time interval of the flow rate pulse. , a timer for measuring the time interval of the flow rate pulses in the arithmetic processing unit;
Compare the time interval measured by the timer with a predetermined time, and if the measured time interval is shorter than the predetermined time, calculate the average value of a predetermined number of the time intervals stored in the storage unit, and Calculate the flow rate per unit time from the average value, and if the measured time interval is longer than a predetermined time,
A flow rate measuring device comprising a calculation processing section that calculates the flow rate per unit time from the measurement time interval or the average value of the measurement time and the previous measurement time.