JP3640334B2 - Flow meter and gas meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow meter and a gas meter for measuring a flow rate of a fluid such as a gas.
[0002]
[Prior art]
In addition to the instantaneous flow meter that measures the flow rate of fluid per unit time (hereinafter referred to as the instantaneous flow rate), the flow meter continuously or intermittently integrates the instantaneous flow rate (hereinafter referred to as the instantaneous flow rate). There is an integrated flow meter (hereinafter also referred to as an integrated flow meter) that measures an integrated flow rate.
[0003]
FIG. 11 is a configuration diagram showing an outline of a conventional integrating flow meter. A conventional integrating flow meter includes, for example, an instantaneous flow rate sensor 101 attached to a pipe 102 through which a fluid 100 such as gas flows, a flow rate calculation unit 103 connected to the instantaneous flow rate sensor 101, and the flow rate calculation unit 103. And a display unit 104 connected to the. As the instantaneous flow sensor 101, for example, a sensor such as a thermal flow sensor or an ultrasonic flow sensor is used.
[0004]
In this flow meter, the instantaneous flow rate sensor 101 is driven continuously or intermittently, and a signal corresponding to the flow rate per unit time of the fluid 100 flowing through the pipe 102 is output. The flow rate calculation unit 103 calculates the instantaneous flow rate based on the output signal output from the instantaneous flow rate sensor 101 continuously or intermittently, and integrates the instantaneous flow rate continuously or intermittently. The flow rate is calculated. The integrated flow rate calculated by the flow rate calculation unit 103 is displayed on the display unit 104.
[0005]
FIG. 12A shows an example of the instantaneous flow rate obtained when the instantaneous flow rate sensor 101 is continuously driven. In this figure, the horizontal axis indicates time, and the vertical axis indicates the instantaneous flow rate value. In this figure, time t₀To constant flow rate Q₀The result is shown when
[0006]
FIG. 12B shows an example of the integrated flow rate calculated based on the instantaneous flow rate shown in FIG. In this figure, the horizontal axis indicates time, and the vertical axis indicates the value of the integrated flow rate. The flow rate calculation unit 103 continuously integrates the instantaneous flow rate shown in FIG. 12A to output a value of the integrated flow rate that increases with a constant slope as shown in FIG. 12B. This integrated flow rate is displayed on the display unit 104.
[0007]
As described above, the integrated flow rate can be calculated by driving the instantaneous flow rate sensor 101 continuously in time and continuously integrating the sensor output value. Further, the integrated flow rate can be calculated by driving the instantaneous flow rate sensor 101 intermittently and sequentially adding a value obtained by multiplying the intermittent instantaneous flow rate by the measurement time interval.
[0008]
[Problems to be solved by the invention]
By the way, the thermal type flow rate sensor and the ultrasonic type flow rate sensor used as the instantaneous flow rate sensor 101 described above require electric power at the time of driving. Therefore, when driving continuously, it is combined with other circuit elements. Therefore, there is a problem that power consumption tends to increase. This problem becomes a serious problem particularly in the case of a flow meter such as a battery-driven flow meter, for example, a portable flow meter or a gas meter that does not use commercial power attached to each gas consumer.
[0009]
On the other hand, such a problem of power consumption is alleviated by driving the instantaneous flow rate sensor 101 intermittently. However, when the instantaneous flow rate sensor 101 is intermittently driven, a measurement error may occur when the flow of the fluid 100 to be measured includes a pulsation component due to disturbance. For example, when the measurement interval of the instantaneous flow rate sensor 101 is an integral multiple of the period of the pulsating component, a measurement error occurs.
[0010]
13 and 14 are explanatory diagrams for explaining a pulsation component due to disturbance. FIG. 13 shows a case where a fluid 100 such as a gas is supplied to each consumer A, B, and C through each of the flow paths 161, 162, and 163 branched from one flow path 160. The integrated flow rate of the fluid 100 supplied to each consumer is measured by integrated flow meters 164, 165, 166 installed in the respective flow paths.
[0011]
FIG. 14A is a diagram showing a change in the flow rate of the fluid 100 used by the consumer A shown in FIG. In this figure, the vertical axis indicates the instantaneous flow rate, and the horizontal axis indicates time. In the example of this figure, the consumer A has a time t_AUntil constant flow Q_AWas consumed at the time t_AThis shows the case where a load element whose consumption flow rate fluctuates greatly is used. Here, as the load element, for example, when a gas is used as the fluid 100, there are a heat pump, an engine, a blower, and the like. These load elements not only have a large amount of consumption of the fluid 100, but also the amount of consumption greatly fluctuates, for example, with a period t, and has a period of about 2 Hz to 20 Hz, for example. The load element that causes such a period t may affect the flow of the fluid 100 in an adjacent consumer as a disturbance.
[0012]
FIG. 14B is a diagram showing a change in the flow rate of the fluid 100 observed by the consumer B when the consumer A consumes gas or the like as shown in FIG. In this figure, the vertical axis indicates the instantaneous flow rate, and the horizontal axis indicates time. Consumer B always has a constant flow rate Q_BEven when the customer A is using, the time t when the adjacent consumer A starts using a load element such as a heat pump._AThereafter, a sine wave-like pulsating component with period t is detected.
[0013]
Here, even if the integrating flow meter 165 of the consumer B detects a pulsating component with a period t, the pulsating component is not instantaneous flow rate Q._BTherefore, if the instantaneous flow rate is continuously measured and the instantaneous flow rate is continuously integrated, the obtained integrated flow rate has no influence of the pulsating component. However, when the instantaneous flow rate is intermittently measured at a fixed measurement interval and the integrated flow rate is obtained by multiplying the instantaneous flow rate by the measurement interval, the value of the integrated flow rate has an influence of the pulsating component.
[0014]
15 and 16 are explanatory diagrams for explaining a case where an erroneous flow rate is measured by the consumer B due to the influence of the pulsating component. In these figures, the vertical axis of (A) indicates the instantaneous flow rate, and the horizontal axis indicates time. In these figures, the vertical axis of (B) indicates the integrated flow rate, and the horizontal axis indicates time. Moreover, in these figures, although the consumer A uses load elements, such as a heat pump, the consumer B has shown the value of the flow volume observed when the fluid 100 is not consumed at all.
[0015]
FIG. 15 (A) shows the change in the instantaneous flow rate observed in the integrating flow meter 165 of the consumer B, and this instantaneous flow rate includes a pulsating component with a period t due to the influence of the disturbance from the consumer A. ing. In this figure, when the instantaneous flow sensor of the integrating flow meter 165 of the consumer B is intermittently driven at a constant period T, the measurement position by the instantaneous flow sensor is indicated by a circle. Also, in this figure, the driving cycle T of the instantaneous flow rate sensor is twice the pulsating component cycle t, that is, T = 2t, and the time of each driving timing related to the intermittent driving of the instantaneous flow rate sensor is the positive of the pulsating component. Peak time (time t_B10, T_B11, ......) and the case of synchronization. In this case, the instantaneous flow rate of the consumer B, which should be zero, is always a positive flow rate Q._B10Will be measured as.
[0016]
FIG. 15B shows the value of the integrated flow measured by the consumer B's integrated flow meter 165 when the instantaneous flow sensor is driven in the state shown in FIG. The accumulated flow rate of the consumer B is the time t_B10After that, V_B10= Q_B10× T, V_B11= V_B10+ Q_B10× T ... Thus, the consumer B does not use gas, but the instantaneous flow rate Q_B1As a result, the flow rate is accumulated as if it were used continuously.
[0017]
In FIG. 16A, the driving cycle T of the instantaneous flow rate sensor is twice the cycle t of the pulsating component, that is, T = 2t, and the time of each driving timing related to the intermittent driving of the instantaneous flow rate sensor is the pulsating component. Negative peak time (time t_B20, T_B21, ......) and the case of synchronization. In this case, the instantaneous flow rate of the consumer B, which should be essentially zero, is always a negative flow rate Q._B10Will be measured as. FIG. 16B shows the value of the integrated flow measured by the integrated flow meter 165 of the consumer B when the instantaneous flow sensor is driven in such a state. The accumulated flow rate of the consumer B is the time t_B20After that, V_B20= Q_B20× T, V_B21= V_B20+ Q_B20× T ... In this case, the total flow meter 165 of the consumer B is_B20Thereafter, it is accumulated on the negative side and an incorrect integrated value is indicated.
[0018]
As described above, when the instantaneous flow rate sensor is driven intermittently to reduce the power consumption of the flow meter, measurement errors may occur when the fluid flow contains pulsation components due to disturbance. There is.
[0019]
The present invention has been made in view of such problems, and an object thereof is to provide a flow meter and a gas meter that can reduce power consumption without deteriorating measurement accuracy.
[0020]
[Means for Solving the Problems]
  The flowmeter according to claim 1 is intermittently driven at different time intervals according to the flow rate of the fluid passing through the flow path, and outputs an instantaneous flow rate detection unit that outputs a signal according to the flow rate per unit time. Integrated flow rate calculation means for calculating the integrated flow rate of the fluid based on the output signal from the instantaneous flow rate detection meansThe instantaneous flow rate detecting means is driven at shorter time intervals when the fluid flow rate is in the small flow rate range than when the fluid flow rate is in the large flow rate range.
[0021]
  In this flow meter, a signal corresponding to the flow rate per unit time is output from the instantaneous flow rate detection means that is intermittently driven at different time intervals according to the flow rate of the fluid passing through the flow path. The integrated flow rate calculation means calculates the integrated flow rate of the fluid based on the output signal from the instantaneous flow rate detection means.The instantaneous flow rate detection means is driven at a shorter time interval when the flow rate of the fluid is in a small flow rate range that is susceptible to pulsation than when the flow rate is in a high flow rate range.
[0024]
  Claim2The flow meter according to claim 1, wherein the instantaneous flow rate detecting means is driven at random time intervals, and when the fluid flow rate is in the small flow rate range, the flow rate is in the large flow rate range. It is designed to be driven at shorter time intervals than in some cases.
[0025]
In this flow meter, the instantaneous flow rate detecting means is driven at random time intervals, and measurement errors due to pulsation are reduced. Further, when the flow rate of the fluid is in a small flow rate range that is easily affected by pulsation, the instantaneous flow rate detection means is driven at a shorter time interval than when the flow rate is in the high flow rate range.
[0026]
  Claim3The described gas meter is intermittently driven at different time intervals according to the flow rate of the gas passing through the flow path, and outputs an instantaneous flow rate detection unit that outputs a signal according to the flow rate per unit time, and an instantaneous flow rate detection unit Integrated flow rate calculation means for calculating the integrated flow rate of gas based on the output signal fromThe instantaneous flow rate detecting means is driven at shorter time intervals when the gas flow rate is in the small flow rate range than when the gas flow rate is in the large flow rate range.
[0027]
In this gas meter, a signal corresponding to the flow rate per unit time is output from the instantaneous flow rate detection means that is intermittently driven at different time intervals according to the flow rate of the gas passing through the flow path. Further, the integrated flow rate calculation means calculates the integrated flow rate of the gas based on the output signal from the instantaneous flow rate detection means.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0029]
FIG. 1 is a configuration diagram showing an outline of a flow meter according to an embodiment of the present invention. The flow meter shown in this figure is for obtaining the integrated flow rate of the fluid 2 flowing through the pipe 1, and is used, for example, as a gas meter. As the fluid 2, a gas such as a gas or a liquid is used. The flow meter shown in this figure includes an instantaneous flow rate sensor 20 attached to the pipe 1, a control unit 21 connected to the instantaneous flow rate sensor 20, and a display unit 22 connected to the control unit 21. Yes. The instantaneous flow rate sensor 20 corresponds to “instantaneous flow rate detection means” in the present invention, and the control unit 21 corresponds to “integrated flow rate calculation means” in the present invention.
[0030]
In this flow meter, the instantaneous flow rate sensor 20 is intermittently driven at a time interval corresponding to the flow rate, and a signal corresponding to the flow rate per unit time of the fluid 2 flowing through the pipe 1 is output. In addition, the control unit 21 calculates the instantaneous flow rate based on the output signal intermittently output from the instantaneous flow rate sensor 20 and calculates the integrated flow rate by intermittently integrating the instantaneous flow rate. It has become. The integrated flow rate calculated by the control unit 21 is displayed on the display unit 22. The drive timing of the instantaneous flow rate sensor 20 will be described in detail later with reference to the drawings.
[0031]
FIG. 2 is a configuration diagram illustrating an example of the instantaneous flow rate sensor 20. The flow sensor 20a shown in this figure is one of so-called thermal flow sensors, the temperature sensor 3 disposed on the upstream side, the temperature sensor 5 disposed on the downstream side of the temperature sensor 3, The heater 4 is provided between the temperature sensor 3 and the temperature sensor 5. This flow rate sensor 20a obtains a flow rate corresponding to the flow rate of the fluid 2 flowing through the flow path from the power supplied to the heater 5 necessary to keep the temperature difference detected by the two temperature sensors 3, 5 constant, When the heater 4 is heated with a constant current or a constant power, the flow rate can be obtained from the difference in temperature detected by the two temperature sensors 3 and 5. The temperature sensors 3 and 5 utilize, for example, the fact that the resistance value of the platinum thin film resistor changes with temperature.
[0032]
FIG. 3 is a configuration diagram illustrating another example of the instantaneous flow rate sensor 20. The flow sensor shown in this figure is one of so-called ultrasonic flow sensors, and a pair of transceivers 31 disposed diagonally opposite to the flow direction of the fluid 2 on the pipe wall of the pipe 1 and A transceiver 32 is provided. The transmitter / receiver 31 and the transmitter / receiver 32 can transmit ultrasonic waves to each other and receive ultrasonic waves transmitted from the other party. Here, the ultrasonic wave 33 transmitted from the transmitter / receiver 32 toward the transmitter / receiver 31 includes a forward component of the flow of the fluid 2. The ultrasonic wave 34 transmitted from the transmitter / receiver 31 to the transmitter / receiver 32 includes a component in the reverse direction of the flow of the fluid 2. For this reason, in the ultrasonic wave 33 and the ultrasonic wave 34, a time difference corresponding to the flow velocity of the fluid 2 is generated before being received by the transmitter / receiver 31 and the transmitter / receiver 32. Therefore, based on this time difference, the flow rate corresponding to the flow velocity of the fluid 2 can be obtained.
[0033]
Here, the instantaneous flow rate sensor 20 is not limited to the thermal flow rate sensor 20a or the ultrasonic flow rate sensor described above, and a sensor having a structure different from these may be used. In the following description, the instantaneous flow rate sensor 20 is a thermal flow rate sensor 20a.
[0034]
FIG. 4 is a block diagram showing a detailed circuit configuration of the flow meter according to the present embodiment. As shown in this figure, the flow meter according to the present embodiment includes a bridge circuit 6 connected to the temperature sensors 3 and 5 of the flow sensor 20a as components of the control unit 21, and a connection to the bridge circuit 6. Amplifier 7, sampling circuit 8 connected to the amplifier 7, A / D converter 9 connected to the sampling circuit 8, and CPU (central processing unit) 10 connected to the A / D converter 9. And a heater drive circuit 12 connected to the heater 4 of the flow rate sensor 20a, and a timing circuit 13 connected to each of these components. The CPU 10 is connected to the display unit 22. In addition, the flow meter according to the present embodiment has a battery 11 that supplies power Vcc to each component of the flow meter.
[0035]
In the flow meter of the present embodiment, the heater 4 is driven by the heater drive circuit 12 so that the fluid 2 in the vicinity of the heater 4 is heated so as to exhibit a certain temperature rise. The temperature of the fluid 2 in the vicinity of the heater 4 is detected by an upstream temperature sensor 3 and a downstream temperature sensor 5.
[0036]
The change in resistance value of the temperature sensors 3 and 5 is converted into a change in voltage by the bridge circuit 6. The voltage signal S4 of the bridge circuit 6 becomes a signal S5 amplified by the amplifier 7, and is input to the sampling circuit 8. The sampling circuit 8 samples the output signal S5 of the amplifier 7 at a predetermined interval, which will be described in detail later, based on the measurement timing signal S3 from the timing circuit 13, and outputs a signal S6.
[0037]
The output signal S6 of the sampling circuit 8 is converted into a digital signal S7 by the A / D converter 9 and input to the CPU 10 to obtain an integrated value of the flow rate. The CPU 10 outputs a control signal S9 to the timing circuit 13 to control the drive timing of each part. Further, the CPU 10 outputs a signal S8 corresponding to the obtained integrated value to the display unit 22, and displays the integrated value of the flow rate on the display unit 22.
[0038]
The timing circuit 13 outputs a heater drive signal S1 to the heater drive circuit 12 based on the control signal S9 from the CPU 10 and measures the measurement system including the bridge circuit 6, the amplifier 7, the sampling circuit 8, and the A / D converter 9. A timing signal S3 is output. In the flow meter of the present embodiment, the power supply Vcc is supplied to each part by the battery 11, but as will be described in detail later, the drive timing of each part is optimally controlled according to the flow rate, thereby reducing the power supply Vcc. It ensures both power consumption and measurement accuracy.
[0039]
FIG. 5 is an explanatory diagram showing the drive timing of the flow sensor 20a in the present embodiment. In this figure, (A) shows the timing for the heater drive signal S 1 output from the timing circuit 13 to the heater drive circuit 12. The heater drive circuit 12 causes a drive current to flow through the heater 4 in synchronization with the heater drive signal S1. (B) shows a change in the temperature S2 in the vicinity of the heater 4. FIG. The temperature S2 in the vicinity of the heater 4 does not change simultaneously with the heater drive signal S1 due to the thermal time constant, and the rise time t_r(Time t₂₀~ Time t_{twenty one}And fall time t_f(Time t_{twenty four}~ Time t_{twenty five}In each case, there is a time delay of several tens of ms. (C) shows the timing for the measurement timing signal S3 output from the timing circuit 13 to the measurement system such as the sampling circuit 8. The measurement timing signal S3 is generated during a period in which the temperature near the heater 4 is stable (time t_{twenty one}~ Time t_{twenty four}(Between). Then, during the period of the measurement timing signal S3 (time t_{twenty two}~ Time t_{twenty three}In the meantime, the instantaneous flow rate of fluid 2 is measured.
[0040]
Next, the operation of the flow meter having the above configuration will be described.
[0041]
FIG. 6 is a flowchart for explaining the basic operation of the flowmeter according to the present embodiment. In the present embodiment, in order to reduce power consumption, the flow rate sensor 20a and components for driving the flow rate sensor 20a operate intermittently. First, the basic flow of this intermittent operation will be described.
[0042]
First, the CPU 10 activates the timing circuit 13 by transmitting a control signal S9 (step S11). Next, the timing circuit 13 outputs a heater drive signal S1 to the heater drive circuit 12, and starts heating the heater 4 of the flow rate sensor 20a (step S12). Here, as described above, it takes several tens of milliseconds for the temperature in the vicinity of the heater 4 to stabilize after the heating of the heater 4 is started.
[0043]
Next, after a period in which the temperature in the vicinity of the heater 4 is considered to be stable, a measurement timing signal is sent from the timing circuit 13 to the bridge circuit 6, amplifier 7, sampling circuit 8 and A / D converter 9 constituting the measurement system. S3 is transmitted and the measurement system is activated (step S13). Each circuit of the measurement system is also stabilized before the temperature near the heater 4 is stabilized, and the measurement system acquires the output signal output from the flow sensor 20a as measurement data (step S14). When the measurement data is acquired in the measurement system, the CPU 10 immediately stops the output of the heater drive signal S1 to the heater drive circuit 12 and stops the heating of the heater 4 (step S15). The reason why heating of the heater 4 is immediately stopped is because the heater 4 consumes the most power.
[0044]
Next, the measurement data converted into the digital signal S7 in the A / D converter 9 is sent to the CPU 10 (step S16). Thereby, the substantial measurement sequence per one time is completed, each circuit of the measurement system is stopped (step S17), and the timing circuit 13 is stopped (step S18). The CPU 10 calculates an instantaneous flow rate based on the measurement data, and sequentially adds a value obtained by multiplying the instantaneous flow rate by the driving interval of the flow rate sensor 20a to obtain an integrated flow rate. The integrated flow rate obtained by the CPU 10 is output and displayed on the display unit 22.
[0045]
Next, the drive interval of the flow sensor 20a set in the flow meter of the present embodiment will be described. In the present embodiment, the driving interval of the flow rate sensor 20a is varied according to the flow rate.
[0046]
FIG. 7 is a flowchart for explaining setting of the drive interval of the instantaneous flow rate sensor 20a in the present embodiment. The CPU 10 calculates and acquires the value of the instantaneous flow rate of the fluid 2 based on the measurement data from the instantaneous flow rate sensor 20a (step S21). Next, the CPU 10 determines whether or not the acquired instantaneous flow rate value exceeds a predetermined value Q1 set in advance (step S22). Here, for example, when the flow meter is used as a general gas meter, the predetermined value Q1 is set to about 300 liter / h. However, the predetermined value Q1 is not limited to this value.
[0047]
When the value of the instantaneous flow rate exceeds the predetermined value Q1 (Y), the CPU 10 controls the start timing of the timing circuit 13 so that the drive interval of the flow rate sensor 20a becomes long (step S23). Further, when the instantaneous flow rate value does not exceed the predetermined value Q1 (N), the CPU 10 controls the start timing of the timing circuit 13 so that the drive interval of the flow rate sensor 20a is shortened (step S24). Thereby, for example, the driving interval of the flow rate sensor 20a becomes longer in the large flow rate region, and the driving interval of the flow rate sensor 20a becomes shorter in the small flow rate region.
[0048]
Next, the drive interval of the flow sensor 20a will be described in more detail with reference to FIGS. In these figures, the vertical axis indicates the instantaneous flow rate and the horizontal axis indicates time. In these drawings, (A) is a diagram for explaining a driving interval in a small flow rate region, and (B) is a diagram for explaining a driving interval in a large flow rate region. In these drawings, a substantial flow rate measurement position by the flow sensor 20a is indicated by a black circle.
[0049]
FIG. 8 is a diagram for explaining a method for setting the driving interval of the flow rate sensor 20a applied when there is almost no pulsation component due to disturbance in the flow of the fluid 2. In this case, the driving interval τ0 ′ in the large flow rate region (FIG. 8B) is set longer than the driving interval τ0 of the flow rate sensor 20a in the small flow rate region (FIG. 8A). Thereby, the time of each drive timing which concerns on the intermittent drive of the flow sensor 20a in a small flow area is time t1, t2, t3. . . It becomes. Also, the drive timing of the flow rate sensor 20a in the large flow rate range is the time t1 ', t2', t3 '. . . It becomes. Note that if the driving interval τ0 in the small flow rate region is lengthened, the cycle in which the flow rate sensor 20a is intermittently driven becomes longer and the power consumption is greatly reduced, but the measurement accuracy also decreases, so for example, about 1 to 3 seconds. Determined to the extent. Further, the driving interval τ0 ′ in the large flow rate region is set to a value about twice the driving interval τ0, for example.
[0050]
Here, the reason why the drive interval τ0 ′ in the large flow rate region is set to be long will be described. For example, even when there is a pulsation component due to disturbance, the magnitude of the pulsation itself does not change with the flow rate. Therefore, as the flow rate increases, the proportion of the influence of pulsation on measurement accuracy becomes relatively small. For this reason, in a large flow rate region, even if the drive interval of the flow rate sensor 20a is increased, the measurement accuracy does not deteriorate. In addition, by setting the driving interval τ0 ′ in the large flow rate region to be long, the power consumption can be suppressed low.
[0051]
FIG. 9 is a diagram for explaining an example of a method for setting the driving interval of the flow rate sensor 20a that is applied when there is a pulsation component that is large enough to affect the measurement of the flow rate. In this example, the drive timing of the flow sensor 20a is randomly changed so that the pulsation component does not affect the integrated flow value. That is, in this example, a basic basic driving interval τa (τa ′) that is a basic is set in advance, and the driving timing is randomly varied within the basic driving interval τa. In this case, the basic drive interval τa ′ in the large flow rate region (FIG. 9B) is longer than the basic drive interval τa of the flow rate sensor 20a in the small flow rate region (FIG. 9A).
[0052]
Here, the start times t1, t2, t3. . . (T1 ′, t2 ′, t3 ′...), Drive timing times ta, tb, tc. . . If the time to (ta ′, tb ′, tc ′...) Is τn,
τn = rnd (n) × τa
It becomes. However, n is an integer of 1 or more, and rnd (n) is an nth random number of 0 or more and less than 1. Thereby, the time of each drive timing which concerns on the intermittent drive of the flow sensor 20a becomes random, and the influence on the integrated flow value of a pulsation component is prevented.
[0053]
FIG. 10 is a diagram for explaining another example of a method for setting the driving interval of the flow rate sensor 20a applied when there is a pulsation component that is large enough to affect the measurement of the flow rate. In this example, as in the case of FIG. 8, the pulsation component affects the integrated flow rate value by randomly changing the drive interval of the flow rate sensor 20a without setting the basic drive interval τa (τa ′). I am trying not to. In this case, the drive intervals τ1 ′, τ2 ′, τ3 ′,... In the large flow rate region (FIG. 10B). . . , Drive intervals τ1, τ2, τ3,... Of the flow rate sensor 20a in the small flow rate region (FIG. 10A). . . Longer than that. Thereby, the time of each drive timing which concerns on the intermittent drive of the flow sensor 20a in a small flow area is time t1, t2, t3. . . It becomes. Also, the drive timing of the flow rate sensor 20a in the large flow rate range is the time t1 ', t2', t3 '. . . It becomes.
[0054]
In this example, if the minimum interval of the drive timing is tmin and the maximum interval is tmax, the drive interval τn is
τn = tmin + (tmax−tmin) × rnd (n)
It becomes. Note that tmin is determined by the limit of power consumption and the response time of the flow sensor, and is about 0.1 seconds in this embodiment. Also, tmax is determined by the required measurement accuracy, and is about 1 to 3 seconds in the present embodiment.
[0055]
In the above description, the three methods shown in FIGS. 8 to 10 are shown as the method for setting the movement interval. However, in practice, when it is known in advance whether or not there is a pulsation component in the measurement environment, The drive interval is set by any one method suitable for the environment. Further, depending on whether or not there is a pulsating component, one flow meter may be used for a plurality of drive interval setting methods. In this case, the determination as to whether or not there is a pulsating component may be made, for example, by sampling the instantaneous flow rate at a certain interval and determining based on this.
[0056]
As described above, according to the flow meter according to the present embodiment, the instantaneous flow rate sensor 20 is intermittently driven at different time intervals according to the flow rate of the fluid 2, and the output signal from the instantaneous flow rate sensor 20 is output. Since the integrated flow rate is calculated based on the above, power consumption can be reduced without deteriorating measurement accuracy.
[0057]
In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible. For example, in the above-described embodiment, the drive interval is made different between two cases of a large flow rate and a small flow rate. However, the drive interval may be made to be divided into three or more stages.
[0058]
【The invention's effect】
  As explained above, claim 1Or 2Flow meter or claim3According to the described gas meter, since the integrated flow rate is calculated based on the output signal from the instantaneous flow rate detection means that is intermittently driven at different time intervals according to the flow rate, the measurement accuracy is not deteriorated. The power consumption can be reduced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an outline of a flow meter according to an embodiment of the present invention.
2 is a configuration diagram showing an example of an instantaneous flow rate sensor in the flow meter shown in FIG. 1. FIG.
3 is a configuration diagram showing another example of an instantaneous flow rate sensor in the flow meter shown in FIG. 1. FIG.
4 is a block diagram showing a detailed circuit configuration of the flow meter shown in FIG. 1. FIG.
FIG. 5 is an explanatory diagram showing drive timing of the flow sensor shown in FIG. 2;
FIG. 6 is a flowchart for explaining the basic operation of the flowmeter according to the present embodiment.
FIG. 7 is a flowchart for explaining setting of a driving interval of the instantaneous flow rate sensor in the present embodiment.
FIG. 8 is an explanatory diagram showing an example of setting a driving interval of the instantaneous flow rate sensor according to the present embodiment.
FIG. 9 is an explanatory diagram showing another example of setting the drive interval of the instantaneous flow rate sensor according to the present embodiment.
FIG. 10 is an explanatory diagram showing another example of a tray for setting a driving interval of an instantaneous flow rate sensor according to the present embodiment.
FIG. 11 is a block diagram showing an outline of a conventional flow meter.
FIG. 12 is an explanatory diagram showing an instantaneous flow rate and an integrated flow rate obtained when the instantaneous flow rate sensor is driven continuously.
FIG. 13 is an explanatory diagram for explaining a pulsation component due to disturbance.
FIG. 14 is another explanatory diagram for explaining a pulsation component due to disturbance.
FIG. 15 is an explanatory diagram for explaining a measurement error that occurs in a conventional flow meter.
FIG. 16 is another explanatory diagram for explaining a measurement error that occurs in a conventional flow meter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Piping, 2 ... Fluid, 3, 5 ... Temperature sensor, 4 ... Heater, 6 ... Bridge circuit, 7 ... Amplifier, 8 ... Sampling circuit, 10 ... CPU, 11 ... Battery, 12 ... Heater drive circuit, 13 ... Timing Circuit, 20 ... instantaneous flow rate sensor, 21 ... control unit, 22 ... display unit.

Claims (3)

An instantaneous flow rate detecting means that is intermittently driven at different time intervals according to the flow rate of the fluid passing through the flow path and outputs a signal according to the flow rate per unit time;
Based on an output signal from the instantaneous flow rate detecting means, an integrated flow rate calculating means for calculating an integrated flow rate of the fluid;
With
The instantaneous flow rate detecting means is driven at a shorter time interval when the flow rate of the fluid is in a small flow rate range than when the flow rate is in a large flow rate range .   The instantaneous flow rate detecting means is driven at random time intervals, and when the flow rate of the fluid is in a small flow rate range, it is driven at a shorter time interval than when the flow rate is in a large flow rate range. The flow meter according to claim 1. Instantaneous flow rate detection means that is intermittently driven at different time intervals according to the flow rate of the gas passing through the flow path, and outputs a signal according to the flow rate per unit time;
Based on an output signal from the instantaneous flow rate detecting means, integrated flow rate calculating means for calculating the integrated flow rate of the gas;
With
The instantaneous flow rate detecting means is driven at a shorter time interval when the gas flow rate is in the small flow rate range than when the gas flow rate is in the large flow rate range .

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