JP2008180741A - Flow measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flow measuring instrument of high flow measuring precision, by measuring an offset amount, and by subtraction-canceling it in flow measurement thereinafter. <P>SOLUTION: Leakage or offset is determined based on fluctuation in a measured flow rate value of a flow detecting means 2 under the condition where a flow passage opening and closing means 1 is closed to bring a flow rate into zero, when the measured flow rate value of the flow detecting means 2 is the minimum using flow rate or less of gas using equipment continuously for a prescribed time. The leakage and the offset amount are thereby measured precisely at proper timing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a flow rate measuring device for measuring a flow rate of gas or the like.

  As shown in FIG. 5, this type of conventional flow rate measuring device includes a flow rate detection unit 2 such as a thermal flow sensor in a part of the fluid conduit 6, and starts flow rate measurement by a signal from the control means 7 The output signal is amplified or digitized by the signal processing means 10, and the flow rate is calculated by the flow rate calculation means 4. Thus, when the flow rate is measured electronically, even if the actual flow rate flowing through the flow path is zero, various factors (characteristics, variation, temperature change, secular change, etc.) of the electronic component constituting the signal processing means 10 The flow rate calculation result may show a certain value (offset amount).

  This value is added to the original flow rate value and output, and the value itself becomes an error, which decreases the accuracy of flow rate measurement. Therefore, in order to correct this and ensure accuracy, the flow rate measurement value measured by closing the flow channel opening / closing means 1 generally provided on the upstream side of the flow channel and making the flow rate of the flow channel zero is hereinafter referred to as (flow channel opening / closing means). Was canceled from the measured flow rate.

  However, for example, in a gas meter that measures gas consumption for home use, a leak may occur between the gas meter and the gas using appliance. When there is such a leak, a certain flow rate measurement value is continuously detected and cannot be distinguished from the state in which the offset occurs. If a leak has occurred, it is necessary to detect it and close the flow path opening / closing means immediately to stop the gas supply. Conversely, if an offset has occurred, the gas will continue to be used. Although possible, it is necessary to measure the offset amount and cancel the subsequent flow rate measurement in order to ensure the accuracy of the flow rate measurement. In addition, since the measurement of the offset amount needs to be executed when the gas is not used and the flow rate is zero, it is necessary to measure the offset appropriately. Thus, it has been a problem to correctly determine whether leakage or offset occurs at an appropriate time and perform processing corresponding to each.

  In order to solve the above-described problems, the present invention solves the above-mentioned problem by the flow path opening / closing means for opening / closing the flow path, the flow rate detection means for detecting the flow rate of the fluid, and the measured value of the flow rate detection means continuously for a predetermined time. And a control means for closing the flow path opening / closing means and making a leakage judgment from the measured value of the flow rate detection means. An average value of the measured values is obtained, and the average value is subtracted from the measured value of the flow rate detecting means when the flow path opening / closing means is opened and the flow rate measurement is restarted.

  According to the above invention, when a flow rate value not less than a predetermined time and not more than a minimum use flow rate (such as a fire) of a general gas-using device is measured, the flow rate is closed in a state where the flow path opening / closing means is closed and the flow rate is zero. Since the offset is determined, the leakage and the offset amount can be accurately measured at an appropriate timing, the circuit offset amount can be canceled in the subsequent flow rate measurement, and the accuracy of the flow rate measurement can be improved.

According to the flow rate measuring apparatus of the present invention, when the flow rate value from the flow rate detecting means does not change greatly after the flow path opening / closing means is closed when the measured value of the flow rate detecting means is not less than the predetermined time and not more than the predetermined flow rate value. By calculating the average value for a plurality of times by the average calculation means and using this average value as an offset amount, and correcting the flow rate value measured thereafter, the accuracy of flow rate measurement can be ensured.

  The flow rate measuring device according to the present invention includes a flow path opening / closing means for opening and closing a flow path, a flow rate detection means for detecting a flow rate of a fluid, and a measurement value of the flow rate detection means that continues for a predetermined time and is below a predetermined flow rate value. And a control means for making a leak judgment from the measured value of the flow rate detecting means by closing the flow path opening and closing means, and the control means closes the flow path opening and closing means and averages the measured values at the time of leak judgment. And the average value is subtracted from the measured value of the flow rate detecting means when the flow path opening / closing means is opened and the flow rate measurement is resumed. Then, the accuracy of flow rate measurement can be ensured by correcting the offset using the average value at the time of zero flow rate.

  In addition, when the control means closes the flow path opening / closing means and the variation in the measured value of the flow rate detection means is within a predetermined width at the time of leakage judgment, the flow path opening / closing means is closed again at least once, When there is almost no change in the flow rate at the time of leakage judgment, the flow path opening / closing means is closed again, and the offset amount is measured until the flow path opening / closing means is closed for some reason, thereby reducing the accuracy of subsequent flow measurement. Can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the present embodiment.

(Embodiment 1)
FIG. 1 is a block diagram showing a basic configuration necessary for explaining a flow rate measuring apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, the 1st transmitter / receiver 21 which transmits an ultrasonic wave in the middle of the flow path 6, and the 2nd transmitter / receiver 22 which receives are arrange | positioned in the flow direction. Reference numeral 23 denotes transmission means to the first transmitter / receiver 21, and reference numeral 24 denotes amplification means for the signal received by the second transmitter / receiver 22. The amplified signal is compared with the reference signal by the comparison means 25, and a signal equal to or higher than the reference signal is obtained. When it is detected, the ultrasonic signal is repeatedly transmitted by the transmission means 23 through the control means 7 by the repetition means 27 by a preset number of times. Then, the time when the preset number of times of the repeating means 27 is repeated is obtained by the first time measuring means 28 such as a timer counter.

  Next, the switching means 26 switches between transmission / reception of the first transmitter / receiver 21 and the second transmitter / receiver 22, and transmits an ultrasonic signal from the second transmitter / receiver 22 to the first transmitter / receiver 21, that is, from downstream to upstream, The transmission is repeated as described above, and the time is counted. From the time difference, the flow rate calculation unit 29 obtains the flow rate value in consideration of the size of the flow path and the flow state (the flow rate detection unit is configured by the flow rate calculation unit 29 from the first transmitter / receiver 21).

  Further, the control means 4 compares the detected flow rate value with the set value stored in the setting storage means 5, and if the flow rate value is less than the set value, the flow rate is determined based on the time counted by the second timing means 3. Measure the duration that the value is below the set value. Then, it is determined whether or not the continuation time is longer than a preset time (for example, 10 days). When the set value stored in the setting storage means 5 is set to be less than the minimum use flow rate (20-30 L / h for city gas, such as a fire, etc.) of the gas-using device, There is a possibility that a small amount of leakage below the normal usage flow rate of the device or an offset has occurred on the gas usage device side from the flow rate measuring device.

In such a case, the control means 4 closes the flow rate opening / closing means 1 and monitors the change in the flow rate value of the flow rate calculation means 29 to determine whether a leak or an offset occurs. In the case of gas leakage, the flow rate value detected by the flow rate calculation unit 29 gradually decreases after the flow rate switching unit 1 is closed as shown in FIG. Since the flow rate detected by the flow rate calculation means 29 hardly changes even after the flow rate opening / closing means 1 is closed, gas leakage and occurrence of offset are determined. When the control means 4 determines that the gas is leaking, the flow path opening / closing means 1 is closed, the fact that it is leaking is notified by the main body display or the notifying means, and if the offset occurs, the flow rate opening / closing means 1 is closed. Thereafter, the calculated flow rate value is used as an offset amount and subtracted from the subsequent flow rate calculation value to ensure the accuracy of flow rate measurement. In other words, as described above, it is possible to correctly determine whether a leak or an offset occurs and perform processing corresponding to each.

  FIG. 3 is a block diagram of the flow rate measuring device of the present embodiment. The difference from the basic configuration is that a pressure sensor 7 is provided on the gas using device side from the flow path opening / closing means 1. That is, when the flow rate is not more than the set flow rate stored in the setting storage means 5 continuously for a set time as in the basic configuration, the control means 4 closes the flow path opening / closing means 1 and monitors the output of the pressure sensor 7. . When gas leakage occurs, the output of the pressure sensor 7 gradually decreases after the flow rate switching means 1 is closed, and finally becomes about atmospheric pressure. When there is no leakage and the offset, the output of the pressure sensor 7 hardly changes even after the flow rate switching means 1 is closed. From these things, the control means 4 determines leakage and occurrence of offset, and when it is determined that leakage occurs, the flow path opening and closing means 1 is closed and the main body display or notification means notifies the fact that leakage has occurred. If it occurs, the flow rate value after closing the flow rate switching means 1 is set as an offset amount and subtracted from the subsequent flow rate measurement value to ensure the accuracy of the flow rate measurement.

  In this way, it is possible to correctly determine whether a leak or an offset occurs, and perform processing corresponding to each.

(Embodiment 2)
FIG. 4 is a block diagram of the flow rate measuring apparatus according to the second embodiment of the present invention. The difference from the first embodiment is that an average calculating means 8 for calculating an average value of a plurality of flow rate values of the flow rate calculating means at the time of leakage determination is provided. That is, when the flow rate is equal to or lower than the set flow rate stored in the setting storage unit 5 continuously for a set time as in the first embodiment, the control unit 4 closes the flow path opening / closing unit 1 and the flow rate value of the flow rate calculation unit 29. To determine whether leakage or offset occurs. If there is almost no change in the flow rate detected by the flow rate calculation unit 29 even after the flow rate switching unit 1 is closed, the average calculation unit 8 obtains the average value of the flow rate calculation values for a plurality of times. Then, the average value is used as an offset amount and subtracted from the subsequent flow rate calculation value to ensure the accuracy of flow rate measurement. Similarly to the first embodiment, when the flow rate switching means 1 is closed and then the flow rate value decreases and it is determined that there is a leak, the fact that it is a leak is notified by a display or notification means on the main body. In this way, it is possible to correctly determine whether leakage or offset occurs, and perform processing corresponding to each.

  If the flow rate is equal to or lower than the set flow rate stored in the setting storage unit 5 for a set time or longer, the control unit 4 closes the flow path opening / closing unit 1 and monitors the flow rate value of the flow rate calculation unit 29 to determine the flow rate calculation unit. When there is almost no change in the flow rate calculated by 29, the control means 4 is to close the flow path opening / closing means 1 again.

  As described above, when the flow path opening / closing means 1 is closed and leakage is judged to be almost unchanged, it is considered that the flow path opening / closing means 1 has not been completely closed due to some mechanistic factor. That is, when the flow path opening / closing means 1 is not closed due to some mechanical factor, the control means 4 performs the closing control again to reliably close the flow path opening / closing means 1.

The block diagram which shows the basic composition for demonstrating the flow measuring device in Embodiment 1 of this invention. Flow characteristics diagram when the flow path opening / closing means is closed Block diagram of a flow rate measuring device in Embodiment 1 of the present invention Block diagram of a flow rate measuring device in Embodiment 2 of the present invention Block diagram of a conventional flow measurement device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flow path opening / closing means 2 Flow rate detection means 3 2nd time measuring means 4 Control means 5 Setting memory | storage means 6 Flow path

Claims (2)

A flow path opening / closing means for opening / closing a flow path, a flow rate detection means for detecting a flow rate of a fluid, and the flow rate opening / closing means is closed when a measured value of the flow rate detection means continues for a predetermined time and is below a predetermined flow rate value. And a flow rate measuring device comprising a control means for determining leakage from the measured value of the flow rate detection means,
The control means closes the flow path opening / closing means and obtains an average value of a plurality of measurement values at the time of leakage judgment, and opens the flow path opening / closing means to restart the flow rate measurement, and then calculates the average value from the measurement value of the flow rate detection means. A flow measurement device that subtracts. The control means closes the flow path opening / closing means, and when the variation in the measured value of the flow rate detection means is within a predetermined width when judging leakage, the flow path opening / closing means is closed again at least once. The flow rate measuring device described.

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