JP2002139363A - Flow measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow measuring apparatus which reduces power consumption, without causing decrease in the accuracy of measuring flow. SOLUTION: A flow velocity sensor 10 outputs flow velocity information matching the flow velocity of fluid which flows in a fluid supply passage. A correcting operation means 20a-1 performs operation for correcting this flow velocity information into true flow velocity information. A flow computing means 20a-2 computes the flow of the fluid, through the passage based on the true flow velocity information corrected. When the flow velocity information assumes a value equal to or smaller than a prescribed value, an computation halting means 20a-3 causes the operations performed by both means 20a-1 and 20a-2 to be halted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas flow measuring device, and more particularly to a flow rate sensor for outputting flow rate information corresponding to the flow rate of a fluid flowing through a fluid supply path, and a flow rate sensor for removing errors in the flow rate information. And a flow rate calculating device that calculates a flow rate of a fluid flowing through the fluid supply path based on the corrected true flow rate information. .

[0002]

2. Description of the Related Art For example, as a flow rate measuring device used in an electronic gas meter, a device utilizing a hot wire type flow rate sensor (hereinafter, referred to as a flow sensor) capable of accurately measuring a relatively small flow rate is known. . This flow sensor is a sensor that determines the gas flow velocity by utilizing the fact that the movement of heat in the gas supply path is related to the flow velocity of the gas flowing in the supply path.

A flow sensor generally operates using a battery as a power source, and operates intermittently to reduce the power consumption of the battery power source. Therefore, the flow sensor intermittently outputs an electric signal of a magnitude corresponding to the gas flow velocity.

[0004] Since the flow sensor has a high sensitivity, even if gas is not used and a cock downstream of the electronic gas meter is closed, if a disturbance such as a gas pressure fluctuation or a temperature change occurs, the flow sensor is not used. Detects a small flow gas in the forward or reverse direction that slightly flows in the gas supply path due to disturbance. In this case, the cock downstream of the electronic gas meter is closed and no gas is used, so the slight flow rate due to disturbances such as gas pressure fluctuations and temperature changes should be zero when integrated over time. is there.

In view of the above, it has been proposed that a small flow rate caused by disturbance such as a gas pressure fluctuation or a temperature change is offset by integration (Japanese Patent Application Laid-Open Nos. 8-75511 and 8-136298). ).

[0006]

However, in the electronic gas meter using the above-described flow sensor, the flow sensor is operated intermittently in order to reduce power consumption. That is, even if no gas is used and there is no gas flow to be measured, there is a problem that the flow rate calculation is performed and wasteful power consumption is performed.

In particular, in an electronic gas meter having a correction function of correcting the error of the electric signal due to a change in gas temperature and outputting a true electric signal, the above-described power consumption when the gas is not used is provided. Waste is a significant problem.
That is, in the gas meter, when the gas is not used, even if there is no gas flow to be measured, the correction operation must be performed in addition to the flow amount calculation, and further wasteful power consumption is performed. In addition, if the gas flow is very small, the error is small and the effect of the correction calculation is not so large.

Accordingly, an object of the present invention is to provide a flow rate measuring device that reduces power consumption without causing a decrease in flow rate measurement accuracy, focusing on the above-described problems.

[0009]

According to a first aspect of the present invention, there is provided a method for solving the above-mentioned problems, comprising: flow rate information corresponding to a flow rate of a fluid flowing through a fluid supply passage, as shown in FIG. Flow rate sensor 10, a correction calculation unit 20 a-1 that removes an error of the flow rate information and performs a correction calculation for outputting true flow rate information, and based on the corrected true flow rate information, A flow rate measuring device including a flow rate calculating means for calculating a passing flow rate of the fluid flowing through the fluid supply path, wherein when the flow velocity information is equal to or less than a predetermined value, both the correction calculating means and the flow rate calculating means The flow rate measuring device according to the present invention is further characterized by further comprising a calculation stopping means 20a-3 for stopping the calculation.

According to the first aspect of the present invention, the flow rate sensor outputs flow rate information corresponding to the flow rate of the fluid flowing through the fluid supply path. The correction operation unit performs a correction operation for removing the error of the flow velocity information and outputting the true flow velocity information. The flow rate calculation means calculates a flow rate of the fluid flowing through the fluid supply path based on the corrected true flow rate information. When the flow rate information is equal to or less than a predetermined value, the calculation stopping means includes
The calculation by both of the flow rate calculating means is stopped.

Therefore, when the flow rate information is equal to or less than the predetermined value, the calculation by both the correction calculating means and the flow rate calculating means is stopped, so that when the flow rate information is equal to or less than the predetermined value, it is considered that there is substantially no fluid flow rate. It is not necessary to perform the calculation based on the flow velocity information. In addition, when the flow rate of the fluid flowing through the fluid supply passage is small, errors due to the fluid temperature and the like are small. Therefore, even if it is determined that there is no fluid flow velocity based on the flow velocity information that has not been corrected, the flow rate measurement accuracy does not decrease.

According to a second aspect of the present invention, there is provided the flow rate measuring device according to the first aspect, wherein the fluid is a gas, and the operation stopping means is in a predetermined time period in which the gas use frequency is low. Only the flow rate measuring device is characterized in that the calculation is stopped.

According to the second aspect of the present invention, the calculation stopping means stops the calculation only in a predetermined time zone in which the frequency of gas use is low. Therefore, when the time of gas use is low, such as at midnight, there is a high probability that there is no gas flow. For this reason, only in this time zone, if the presence or absence of the fluid flow rate is determined based on the flow rate information that has not been corrected, it is unlikely that there is no passing flow rate despite the fluid being used. .

According to a third aspect of the present invention, there is provided the first or second aspect.
The flow measurement device according to claim 1, wherein the correction calculation unit corrects the flow velocity information based on a temperature of the fluid.

According to the third aspect of the present invention, the correction calculating means corrects the flow velocity information based on the temperature of the fluid.
Therefore, the error of the flow velocity information caused by the fluid temperature is not large when the flow rate of the fluid is very small. For this reason, even if the presence or absence of the fluid flow velocity is determined based on the flow velocity information for which the temperature correction has not been performed, there is not much erroneous determination.

According to a fourth aspect of the present invention, there is provided the flow rate measuring device according to any one of the first to third aspects, wherein the predetermined value is the flow rate information when the passing flow rate is 3 liters / hour. A flow rate measuring device characterized in that:

According to the fourth aspect of the invention, when the fluid is not used, the upper limit of the flow rate of the fluid flowing through the fluid supply path due to disturbance such as pressure fluctuation or temperature change is 3
Paying attention to liter / hour, the predetermined value is set as flow velocity information when the passing flow rate is 3 liter / hour. Therefore, only when the fluid is not being used, the calculation by both the correction calculating means and the flow rate calculating means can be stopped.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram showing an embodiment of an electronic gas meter incorporating the flow rate measuring device of the present invention. As shown in FIG. 1, a hot-wire type flow rate sensor (flow sensor) 10 is provided in a gas supply path, and has a heater 10a and a heater 10 with the heater 10a interposed therebetween.
and a pair of temperature sensors 10b1 and 10b2 that are arranged at equal intervals in the gas flow direction and detect temperature, for example, made of a thermopile.

The temperature sensor 10b1 includes a heater 10a
And outputs a first temperature detection signal.
On the other hand, the temperature sensor 10b2 is disposed downstream of the heater 10a and outputs a second temperature detection signal. Note that the arrow Y1 indicates the gas flow direction.

The heating of the heater 10a is started by a drive current from a heater drive circuit 10c driven under the control of a microcomputer (μCOM) 20.
When the heating of the heater 10a is started, the upstream temperature sensor 10b1 and the downstream temperature sensor 10b2 output temperature detection signals of voltages corresponding to the magnitude of the driving current and the magnitude of the gas flow rate, respectively. This temperature detection signal is amplified by the sensor amplifiers 10d1 and 10d2, respectively.

The temperature detection signals amplified by the sensor amplifiers 10d1 and 10d2 are input to a non-inverting input and an inverting input of a differential amplifier 10e composed of an operational amplifier, respectively. Therefore, the differential amplifier 10e outputs a temperature difference signal corresponding to the difference between the voltages of the two temperature detection signals. This temperature difference signal has a voltage corresponding to the magnitude of the gas flow velocity, becomes larger as the flow velocity increases, is converted into a digital signal by the analog / digital converter (A / D converter) 10f, and is taken into the μCOM 20. It is. As is clear from the above, the temperature difference signal corresponds to the flow velocity information in the claims.

The μCOM 20 is a central processing unit (CPU) 20a that performs various processes according to programs.
A ROM 20b that is a read-only memory storing a processing program and the like executed by the CPU 20a;
A built-in RAM 20c, which is a readable and writable memory having a work area used in various processing steps in a, a data storage area for storing various data, and the like, is interconnected by a bus line (not shown).

The CPU 20a in the μCOM 20 performs a correction process for calculating a true temperature difference signal by correcting an error of the temperature difference signal caused by a gas temperature or the like. CPU 20a
Also, a flow rate calculation process for calculating a passing flow rate by multiplying the true temperature difference signal by a predetermined constant, a flow rate integration process for integrating the calculated passing flow rate to obtain an integrated flow rate, and displaying the calculated integrated flow rate Display processing to be displayed on the display 30 is performed.

The ROM 20b in the μCOM 20
For example, a time zone in which gas is not frequently used, such as between 1:00 am and 4:00 am, and a predetermined value are stored. When the gas is not used,
This is the voltage value of the temperature difference signal when the passing flow rate of 3 liters / hour, which is the upper limit of the passing flow rate of the gas flowing due to disturbance such as pressure fluctuation and temperature change, flows.

The CPU 20a performs a calculation stop process for stopping the correction calculation process and the flow rate calculation process when the gas use frequency is low and the temperature difference signal is equal to or less than a predetermined value. As is clear from the above, the CPU
It can be seen that 20a functions as a correction operation unit, a flow amount operation unit, and an operation stop unit.

As described above, the correction calculation processing and the flow rate calculation processing are stopped when the temperature difference signal is equal to or less than the predetermined value, so that when the temperature difference signal is equal to or less than the predetermined value, it is considered that there is substantially no gas flow velocity. It is not necessary to calculate the passing flow rate based on the leverage temperature difference signal, and power consumption can be reduced. Moreover, when the flow rate of the gas flowing through the gas supply path is very small, the error caused by the gas temperature or the like is small. Therefore, even if it is determined that there is no gas flow velocity based on the uncorrected temperature difference signal, the flow rate measurement accuracy does not decrease.

When the gas usage is low, such as at midnight, there is a high probability that there is no gas flow. Therefore,
As described above, if the presence or absence of the gas flow rate is determined based on the temperature difference signal that has not been corrected only during this time zone,
Despite the use of gas, there is little erroneous determination that there is no gas flow rate, and the flow rate measurement accuracy can be improved.

Further, the predetermined value is set to 3 liters / hour, which is the upper limit of the flow rate of the fluid flowing through the fluid supply path due to disturbance such as pressure fluctuation and temperature change when the gas is not used, The correction calculation process and the flow rate calculation process can be reliably stopped only when the gas is not used.

The operation of the electronic gas meter incorporating the above-described flow rate measuring device will be described below with reference to the processing procedure of the CPU 20a in FIG. First, the CPU 20a drives the heater drive circuit 10c (step S1) to heat the heater 10a. After a lapse of a predetermined time (Y in step S2), the driving of the heater driving circuit 10c is stopped (step S3), and the heating of the heater 10a is stopped. Immediately thereafter, the CPU 20a captures the digital value of the temperature difference signal converted by the A / D converter 10f (Step S).
4).

At this time, if the current time is not a time zone in which the gas stored in the ROM 20b is not frequently used (N in step S5), the process proceeds to steps S6 and S7. On the other hand, even if the current time is a time zone in which the gas is not frequently used (Y in step S5), if the acquired temperature difference signal is larger than a predetermined value (N in step S10), the process proceeds to steps S6 and S7. .

In steps S6 and S7, the temperature difference signal is multiplied by a correction coefficient α that changes according to the gas temperature to correct an error in the temperature difference signal caused by the gas temperature change. The temperature difference signal is multiplied by α with the changing correction coefficient, and a flow rate correction process for correcting an error of the temperature difference signal caused by the change due to the structure of the object or the like is performed, and a true temperature difference signal is calculated. Thereafter, a flow rate calculating process for calculating the passing flow rate by multiplying the true temperature difference signal by a predetermined constant (step S8), and a flow rate integrating process for integrating the calculated passing flow rates to obtain an integrated flow rate are performed ( Step S9), proceed to the display processing of step S11.

On the other hand, the current time is a time zone in which the frequency of use of the gas stored in the ROM 20b is low (Y in step S5), and the acquired temperature difference signal is the ROM 20b.
If the gas flow rate is equal to or less than the predetermined value stored in, it is considered that there is substantially no gas flow rate, and the temperature correction processing, the flow rate correction processing, the flow rate calculation processing and the flow rate integration processing are immediately performed, and the display processing in step S11 is immediately performed. move on.

Then, from step S9 to step S11
When the process proceeds to the display processing of step S9, the result integrated in step S9 is displayed on the display 30. On the other hand, step S1
When the process proceeds from 0 to the display processing of step S11, the integrated flow rate displayed last time is displayed on the display 30.

In the above-described embodiment, the thermal flow rate sensor has been described as the flow rate sensor. However, for example, an ultrasonic sensor may be used. The ultrasonic sensor is constituted by two acoustic transducers, which are, for example, piezoelectric vibrators which operate at an ultrasonic frequency and are arranged at a fixed distance in the gas supply path.

Then, an operation of causing the other transducer to receive an ultrasonic signal generated by one of the transducers is alternately performed so that the ultrasonic signal propagates between the transducers in a gas flow direction and in a direction opposite to the gas flow direction. Are measured intermittently, and the difference between the two measured propagation times is output as flow velocity information.

Also in the case of the ultrasonic sensor, an error occurs in the propagation time difference depending on the gas temperature, the structure of an object, and the like. Therefore, it is necessary to correct the propagation time difference and calculate the true propagation time difference. Therefore, in this case as well, if the correction calculation and the flow rate calculation are stopped when the propagation time difference is equal to or less than the predetermined value, the same effect as in the above embodiment can be obtained.

[0037]

As described above, according to the first aspect of the present invention, when the flow velocity information is equal to or less than the predetermined value, the calculation by both the correction calculation means and the flow rate calculation means is stopped, so that the flow velocity information is reduced to a predetermined value. If the value is equal to or less than the value, it is assumed that there is substantially no fluid flow velocity, and it is not necessary to perform the calculation based on the flow velocity information. In addition, when the flow rate of the fluid flowing through the fluid supply passage is small, errors due to the fluid temperature and the like are small. For this reason, even if it is determined that there is no fluid flow velocity based on the flow velocity information that has not been corrected, the flow measurement accuracy does not decrease even if it is judged that there is no fluid flow velocity. A flow measurement device can be obtained.

According to the second aspect of the present invention, there is a high probability that there is no gas flow rate during a time period when gas usage is low, such as at midnight. For this reason, only in this time zone, if the presence or absence of the fluid flow rate is determined based on the flow rate information that has not been corrected, it is unlikely that there is no passing flow rate despite the fluid being used. Therefore, it is possible to obtain a flow rate measuring device with improved flow rate measurement accuracy.

According to the third aspect of the invention, the error of the flow velocity information caused by the fluid temperature is not large when the flow rate of the fluid is very small. For this reason, even if the presence / absence of the fluid flow velocity is determined based on the flow velocity information for which the temperature correction has not been performed, there is not much erroneous determination, so that it is possible to obtain a flow measurement device with improved flow velocity measurement accuracy.

According to the fourth aspect of the present invention, the calculation by both the correction calculation means and the flow rate calculation means can be stopped only when the fluid is not used reliably, so that the flow rate measurement accuracy is reduced. Without inviting, it is possible to obtain a flow rate measuring device that further reduces power consumption.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration diagram of a flow measurement device of the present invention.

FIG. 2 is a block diagram showing one embodiment of an electronic gas meter incorporating the flow rate measuring device of the present invention.

FIG. 3 is a flowchart showing a processing procedure of a CPU constituting the electronic gas meter of FIG. 3;

[Explanation of symbols]

 Reference Signs List 10 Flow rate sensor (flow sensor) 20a-1 Correction calculation means (CPU) 20a-2 Flow rate calculation means (CPU) 20a-3 Calculation stop means (CPU)

Claims (4)

[Claims] 1. A flow rate sensor that outputs flow rate information according to a flow rate of a fluid flowing through a fluid supply path, and a correction calculation that removes an error in the flow rate information and performs a correction calculation for outputting true flow rate information. Means, based on the corrected true flow rate information, a flow rate measuring device comprising a flow rate calculating means for calculating the flow rate of the fluid flowing through the fluid supply path, when the flow rate information is less than a predetermined value, A flow rate measuring apparatus further comprising a calculation stopping means for stopping the calculations by both the correction calculating means and the flow rate calculating means. 2. The flow rate measuring apparatus according to claim 1, wherein the fluid is gas, and the calculation stopping means stops the calculation only when the predetermined gas usage frequency is low. A flow rate measuring device characterized in that the flow rate is measured. 3. The flow rate measuring device according to claim 1, wherein the correction calculating means corrects the flow velocity information based on a temperature of the fluid. 4. The flow rate measuring device according to claim 1, wherein the predetermined value is the flow rate information when the passing flow rate is 3 liters / hour. Measuring device.