JP4698014B2 - Flow measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas flow rate measuring device, and more particularly, a flow rate sensor that outputs flow rate information corresponding to the flow rate of a fluid flowing in a fluid supply path, and an error in flow rate information is removed to output true flow rate information. The present invention relates to a flow rate measuring device comprising: a correction calculation means for performing the correction calculation; and a flow rate calculation means for calculating a passage flow rate of the fluid flowing through the fluid supply path based on the corrected true flow velocity information.
[0002]
[Prior art]
For example, a flow rate measuring device used in an electronic gas meter is known that uses a hot-wire flow rate sensor (hereinafter referred to as a flow sensor) that can accurately measure a relatively small flow rate. This flow sensor is a sensor for obtaining a gas flow velocity by utilizing the fact that the movement of heat in the gas supply passage is related to the flow velocity of the gas flowing in the supply passage.
[0003]
The flow sensor generally operates using a battery as a power source, and operates intermittently in order to reduce the power consumption of the battery power source. Accordingly, the flow sensor intermittently outputs an electrical signal having a magnitude corresponding to the gas flow rate.
[0004]
Because the flow sensor has good sensitivity, even if no gas is used and the cock downstream of the electronic gas meter is closed, if a disturbance such as gas pressure fluctuation or temperature change occurs, it will be caused by this disturbance. Then, a slight flow gas in the forward direction or the reverse direction slightly flowing in the gas supply path is detected. In this case, because the cock downstream of the electronic gas meter is closed and no gas is used, the slight flow rate due to disturbances such as gas pressure fluctuations and temperature changes should be zero if this is integrated over time. is there.
[0005]
In view of this, conventionally, a method has been considered in which a slight flow rate due to disturbance such as gas pressure fluctuation or temperature change is canceled by integration (Japanese Patent Laid-Open Nos. 8-75511 and 8-136298).
[0006]
[Problems to be solved by the invention]
However, in the electronic gas meter using the flow sensor described above, the flow sensor is operated intermittently in order to reduce power consumption, but the gas flow rate is 0, that is, no gas is used for measurement. Even if there is no gas flow to be performed, there is a problem that the flow rate calculation is performed and wasteful power consumption is performed.
[0007]
In particular, in an electronic gas meter having a correction function that corrects an error in the electrical signal due to a change in gas temperature and outputs a true electrical signal, the power consumption when the gas is not used is wasted. It becomes a remarkable problem. That is, in the above gas meter, when the gas is not used, even if there is no gas flow to be measured, a correction calculation must be performed in addition to the flow rate calculation, and a further wasteful power consumption is performed. Moreover, if the gas flow is very small, the error is small and the effect of the correction calculation is not so great.
[0008]
Accordingly, the present invention focuses on the above-described problems, and 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.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 includes a flow rate sensor 10 that outputs flow rate information corresponding to the flow rate of the fluid flowing in the fluid supply path, as shown in the basic configuration diagram of FIG. Correction operation means 20a-1 for performing a correction operation for removing the error in the flow velocity information and outputting the true flow velocity information, and passage of the fluid flowing through the fluid supply path based on the corrected true flow velocity information In the flow rate measuring device including the flow rate calculation unit 20a-2 for calculating the flow rate, when the flow velocity information is equal to or less than a predetermined value, the calculation stop unit 20a- stops the calculation by both the correction calculation unit and the flow rate calculation unit. 3 is provided in the flow rate measuring device.
[0010]
According to the first aspect of the present invention, the flow velocity sensor outputs flow velocity information corresponding to the flow velocity of the fluid flowing in the fluid supply path. The correction calculation means performs correction calculation for removing the error in the flow velocity information and outputting the true flow velocity information. The flow rate calculation means calculates the passage flow rate of the fluid flowing through the fluid supply path based on the corrected true flow velocity information. When the flow velocity information is less than or equal to a predetermined value, the calculation stop means stops the calculation by both the correction calculation means and the flow rate calculation means.
[0011]
Therefore, when the flow velocity information is equal to or lower than the predetermined value, the calculation by both the correction calculating means and the flow rate calculating means is stopped, and when the flow velocity information is equal to or lower than the predetermined value, it is considered that there is substantially no fluid flow velocity. There is no need to perform an operation based on. Moreover, when the passage flow rate of the fluid flowing through the fluid supply path is very small, there are few errors due to the fluid temperature or the like. For this reason, even if it is determined that there is no fluid flow velocity based on the flow velocity information that is not corrected, the flow measurement accuracy does not decrease.
[0012]
The invention according to claim 2 is the flow rate measuring device according to claim 1, wherein the fluid is gas, and the calculation stop means is only in a predetermined time zone in which the gas usage frequency is low. The present invention resides in a flow rate measuring device characterized by stopping computation.
[0013]
According to the second aspect of the present invention, the calculation stopping means stops the calculation only when the predetermined time period during which the gas is used is low. Therefore, there is a high probability that there is no gas flow rate when the gas usage frequency is low, such as at midnight. For this reason, if the presence or absence of the fluid flow rate is determined based on the flow rate information that has not been corrected only during this time period, it is not often erroneously determined that there is no passing flow rate even though the fluid is used. .
[0014]
A third aspect of the present invention is the flow rate measuring apparatus according to the first or second aspect, wherein the correction calculation unit corrects the flow velocity information based on the temperature of the fluid. Exist.
[0015]
According to the third aspect of the present invention, the correction calculation means corrects the flow velocity information based on the temperature of the fluid. Therefore, the error in the flow rate information due to 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 that is not subjected to temperature correction, there is not much misjudgment.
[0016]
A fourth aspect of the present invention is the flow rate measuring apparatus according to any one of the first to third aspects, wherein the predetermined value is the flow velocity information when the passing flow rate is 3 liters / hour. It exists in the flow measurement device.
[0017]
According to the invention of claim 4, when the fluid is not used, the upper limit of the flow rate of the fluid flowing in the fluid supply path due to disturbance such as pressure fluctuation and temperature change is 3 liters / hour. In particular, let the predetermined value be flow velocity information when the passing flow rate is 3 liters / hour. Therefore, the calculation by both the correction calculation means and the flow rate calculation means can be stopped only when the fluid is not reliably used.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
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 the figure, a hot-wire flow rate sensor (flow sensor) 10 is provided in a gas supply path, and is spaced apart from the heater 10a at an equal interval in the gas flow direction with the heater 10a interposed therebetween. It has a pair of temperature sensors 10b1 and 10b2 that are arranged and detect the temperature, for example, made of a thermopile.
[0019]
The temperature sensor 10b1 is disposed upstream of the heater 10a and outputs a first temperature detection signal. On the other hand, the temperature sensor 10b2 is arranged on the downstream side of the heater 10a and outputs a second temperature detection signal. An arrow Y1 indicates the gas flow direction.
[0020]
Heating of the heater 10 a is started by a driving current from a heater driving circuit 10 c that is driven under the control of the microcomputer (μCOM) 20. When heating of the heater 10a is started, the temperature sensor 10b1 on the upstream side and the temperature sensor 10b2 on the downstream side each output a temperature detection signal having a voltage corresponding to the magnitude of the driving current and the magnitude of the gas flow velocity. The temperature detection signals are amplified by the sensor amplifiers 10d1 and 10d2.
[0021]
The temperature detection signals amplified by the sensor amplifiers 10d1 and 10d2 are respectively input to the non-inverting input and the inverting input of the differential amplifier 10e made of an operational amplifier. Therefore, the differential amplifier 10e outputs a temperature difference signal corresponding to the voltage difference between the two temperature detection signals. This temperature difference signal has a voltage corresponding to the magnitude of the gas flow velocity, and becomes larger as the flow velocity increases. The temperature difference signal is converted into a digital signal by an analog / digital converter (A / D converter) 10f and taken into the μCOM 20. It is. As is clear from the above, it can be seen that the temperature difference signal corresponds to the flow velocity information in the claims.
[0022]
The μCOM 20 includes a central processing unit (CPU) 20a that performs various processes in accordance with a program, a ROM 20b that is a read-only memory that stores a processing program performed by the CPU 20a, a work area that is used in various processes in the CPU 20a, A RAM 20c, which is a readable / writable memory having a data storage area for storing various data, is built in, and these are interconnected by a bus line (not shown).
[0023]
The CPU 20a in the μCOM 20 corrects an error of the temperature difference signal due to the gas temperature or the like and performs a correction process for calculating a true temperature difference signal. The CPU 20a also calculates 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 calculating the calculated integrated flow rate. Display processing to be displayed on the display 30 is performed.
[0024]
Further, the ROM 20b in the μCOM 20 stores a time zone in which the gas is not frequently used, for example, between 1:00 AM and 4:00 AM, and a predetermined value. The predetermined value is the voltage value of the temperature difference signal when a flow rate of 3 liters / hour, which is the upper limit value of the flow rate of the flowing gas due to disturbance such as pressure fluctuation and temperature change, flows when the gas is not used. It is.
[0025]
Then, 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, it can be seen that the CPU 20a functions as a correction calculation unit, a flow rate calculation unit, and a calculation stop unit.
[0026]
As described above, when the temperature difference signal is equal to or lower than the predetermined value, the correction calculation process and the flow rate calculation process are stopped. It is not necessary to calculate the passage flow rate based on the difference signal, and the power consumption can be reduced. In addition, when the flow rate of the gas flowing through the gas supply path is very small, there are few errors due to the gas temperature or the like. Therefore, even if it is determined that there is no gas flow rate based on the temperature difference signal that has not been corrected, the flow rate measurement accuracy does not decrease.
[0027]
Moreover, when it is a time zone with low gas use frequency such as midnight, there is a high probability that there is no gas flow rate. Therefore, as described above, if the presence or absence of the gas flow rate is determined based on the temperature difference signal that is not corrected only during this time period, it is erroneously determined that there is no gas flow even though the gas is used. Therefore, the flow rate measurement accuracy can be improved.
[0028]
Furthermore, the predetermined value is set to 3 liters / hour, which is the upper limit value of the flow rate of fluid flowing in the fluid supply path due to disturbance such as pressure fluctuation and temperature change when the gas is not used, so that the gas can be reliably supplied. The correction calculation process and the flow rate calculation process can be stopped only when not in use.
[0029]
The operation of the electronic gas meter incorporating the above-described flow rate measuring apparatus 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. Then, after a predetermined time has elapsed (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 takes in the digital value of the temperature difference signal converted by the A / D converter 10f (step S4).
[0030]
At this time, when the current time is not a time zone in which the gas stored in the ROM 20b is not used frequently (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 captured temperature difference signal is greater than a predetermined value (N in step S10), the process proceeds to steps S6 and S7. .
[0031]
In steps S6 and S7, a temperature correction process that multiplies the temperature difference signal by a correction coefficient α that changes depending on the gas temperature to correct an error of the temperature difference signal caused by the gas temperature change, and a correction that changes depending on the structure of the object. A true temperature difference signal is calculated by multiplying the temperature difference signal by a coefficient and performing a flow rate correction process for correcting an error of the temperature difference signal caused by a change due to the structure of the object. Thereafter, a flow rate calculation process for calculating the passing flow rate by multiplying the true temperature difference signal by a predetermined constant (step S8), and a flow rate integration process for integrating the calculated passing flow rate to obtain an integrated flow rate ( The process proceeds to step S9) and the display process of step S11.
[0032]
On the other hand, when 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 captured temperature difference signal is equal to or less than the predetermined value stored in the ROM 20b. Assuming that there is substantially no gas flow rate, the process immediately proceeds to the display process in step S11 without performing the temperature correction process, the flow rate correction process, the flow rate calculation process, and the flow rate integration process.
[0033]
When the display process proceeds from step S9 to step S11, the result accumulated in step S9 is displayed on the display 30. On the other hand, when the display process proceeds from step S10 to step S11, the integrated flow rate displayed last time is displayed on the display 30.
[0034]
In the above-described embodiment, the thermal type flow rate sensor has been described as the flow rate sensor. However, for example, an ultrasonic type sensor may be used. The ultrasonic sensor is composed of two acoustic transducers composed of, for example, piezoelectric vibrators that operate at an ultrasonic frequency and are spaced apart from each other within a gas supply path.
[0035]
Then, the operation of causing the other transducer to receive the ultrasonic signal generated by one transducer is performed alternately, and the time during which the ultrasonic signal propagates between the transducers in the gas flow direction and in the direction opposite to the gas flow direction is intermittent. The difference between the two propagation times thus measured is output as flow velocity information.
[0036]
Also in the case of the ultrasonic sensor, an error occurs in the propagation time difference depending on the gas temperature, the structure of the object, and the like. Therefore, it is necessary to correct 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 smaller than the predetermined value, the same effect as in the above embodiment can be obtained.
[0037]
【The invention's effect】
As described above, according to the first aspect of the present invention, when the flow velocity information is equal to or lower than the predetermined value, by stopping the calculation by both the correction calculation means and the flow rate calculation means, Assuming that there is substantially no fluid flow velocity, it is not necessary to perform calculations based on this flow velocity information. Moreover, when the passage flow rate of the fluid flowing through the fluid supply path is very small, there are few errors due to the fluid temperature or the like. For this reason, the flow rate measurement accuracy does not decrease even if it is determined that there is no fluid flow rate based on the flow rate information that has not been corrected. Therefore, the power consumption is reduced without causing a decrease in the flow rate measurement accuracy. A flow measuring device can be obtained.
[0038]
According to the second aspect of the present invention, there is a high probability that there is no gas flow rate when the gas usage frequency is low, such as at midnight. For this reason, if the presence or absence of the fluid flow rate is determined based on the flow rate information that has not been corrected only during this time period, it is not often erroneously determined that there is no passing flow rate even though the fluid is used. Therefore, it is possible to obtain a flow rate measuring device that improves flow rate measurement accuracy.
[0039]
According to the third aspect of the present invention, the error in the flow rate information due to 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 that has not been subjected to temperature correction, there is not much misjudgment, and thus a flow measurement device that improves flow velocity measurement accuracy can be obtained.
[0040]
According to the fourth aspect of the invention, since the calculation by both the correction calculation means and the flow rate calculation means can be stopped only when the fluid is not reliably used, the flow measurement accuracy is not reduced. Thus, 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 rate measuring device of the present invention.
FIG. 2 is a block diagram showing an 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]
10 Flow rate sensor (flow sensor)
20a-1 Correction calculation means (CPU)
20a-2 Flow rate calculation means (CPU)
20a-3 Computation stop means (CPU)

Claims (4)

A flow rate sensor that outputs flow rate information corresponding to the flow rate of the fluid flowing in the fluid supply path; a correction calculation unit that performs a correction calculation to output an error in the flow rate information and output true flow rate information; and the correction On the basis of the true flow velocity information, a flow rate measuring device comprising flow rate calculation means for calculating the flow rate of the fluid flowing through the fluid supply path,
A flow rate measuring device further comprising a calculation stop means for stopping calculation by both the correction calculation means and the flow rate calculation means when the flow velocity information is equal to or less than a predetermined value. The flow rate measuring device according to claim 1,
The fluid is a gas;
The flow rate measuring device characterized in that the calculation stop means stops the calculation only when a predetermined time period of low gas use frequency is reached. The flow rate measuring device according to claim 1 or 2,
The flow rate measuring apparatus, wherein the correction calculation unit corrects the flow velocity information based on the temperature of the fluid. The flow rate measuring device according to any one of claims 1 to 3,
The predetermined value is the flow velocity information when the passing flow rate is 3 liters / hour.

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