JP2000039344A - Flowmeter and gas meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce consumption power without degrading measuring accuracy. SOLUTION: An instantaneous flowrate sensor 20 is intermittently driven with a time interval according to the flowrate and outputs signal according to the flowrate per unit time of fluid 2 flowing in a piping 1. A control part 21 calculates instantaneous flowrate based on the output signal intermittently output from the instantaneous flowrate sensor 20 and integrates the instantaneous flowrate to calculate the integral flowrate on an indication part 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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]

2. Description of the Related Art In a flow meter, in addition to an instantaneous flow meter for measuring a flow rate of a fluid per unit time (hereinafter, referred to as an instantaneous flow rate), a fluid is integrated by continuously or intermittently integrating an instantaneous flow rate. There is an integrated flow meter (hereinafter, also referred to as an integrated flow meter) that measures the flow rate (hereinafter, referred to as an integrated flow rate).

FIG. 11 is a configuration diagram schematically showing a conventional integrating type flow meter. A conventional integrating flow meter is, for example,
An instantaneous flow sensor 101 attached to a pipe 102 through which a fluid 100 such as a gas flows;
The flow calculation unit 103 connected to the
3 is connected to the display unit 104. As the instantaneous flow sensor 101, for example, a sensor such as a thermal flow sensor or an ultrasonic flow sensor is used.

In this flow meter, the instantaneous flow sensor 101 is driven continuously or intermittently, and a signal corresponding to the flow rate of the fluid 100 flowing through the pipe 102 per unit time is output. Further, the flow rate calculation unit 103 calculates the instantaneous flow rate based on the output signal continuously or intermittently output from the instantaneous flow rate sensor 101, 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.

FIG. 12A shows an example of an instantaneous flow rate obtained when the instantaneous flow rate sensor 101 is continuously driven. In this figure, the horizontal axis represents time, and the vertical axis represents the value of the instantaneous flow rate. This figure shows a result in a case where a constant value of the instantaneous flow rate Q ₀ flows from the time t ₀ .

FIG. 12B shows an example of an 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, and outputs an integrated flow rate value that increases with a constant slope as shown in FIG. 12B. The integrated flow rate is displayed on the display unit 104.

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. Alternatively, the integrated flow rate can be calculated by intermittently driving the instantaneous flow rate sensor 101 and sequentially adding a value obtained by multiplying the intermittent instantaneous flow rate by the measurement time interval.

[0008]

The thermal flow rate sensor and the ultrasonic flow rate sensor used as the above-mentioned instantaneous flow rate sensor 101 require electric power when driven. However, there is a problem that power consumption tends to increase in combination with other circuit elements.
This is especially true for battery operated flow meters,
For example, a serious problem occurs in the case of a flow meter such as a portable flow meter or a gas meter that does not use commercial power and is attached to each gas consumer.

On the other hand, such a problem of power consumption is reduced by driving the instantaneous flow rate sensor 101 intermittently. However, when the instantaneous flow 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 sensor 101 is an integral multiple of the cycle of the pulsating component, a measurement error occurs.

FIG. 13 and FIG. 14 are explanatory diagrams for explaining a pulsation component due to a disturbance. In FIG.
Channels 161, 162, 1 branched from one channel 160
63 shows a case where a fluid 100 such as a gas is supplied to each of the consumers A, B, and C by each of them. The integrated flow rate of the fluid 100 supplied to each customer is measured by the integrated flow meters 164, 165, 166 installed in the respective flow paths.

FIG. 14A is a view showing the demand A shown in FIG.
FIG. 6 is a diagram showing a change in the flow rate of the fluid 100 used in the method. In this figure, the vertical axis indicates the instantaneous flow rate, and the horizontal axis indicates time. In the illustrated example, consumer A is until the time t _A is a constant flow rate Q _A had consumed fluid 100, flow consumption from time t _A is shows the case of using a loading element which varies significantly I have. Here, as a load element, for example, when gas is used as the fluid 100, a heat pump, an engine, a blower, and the like are used. These load elements not only consume a large amount of the fluid 100 but also vary greatly in the cycle t, for example, and have a cycle of about 2 Hz to 20 Hz, for example. A load element that causes such a cycle t may affect the flow of the fluid 100 at an adjacent consumer as a disturbance.

FIG. 14 (B) shows that the customer A is
FIG. 7 is a diagram showing a change in the flow rate of the fluid 100 observed by the consumer B when the gas or the like is consumed as shown in FIG. In this figure, the vertical axis indicates the instantaneous flow rate, and the horizontal axis indicates time. The consumer B, always even uses certain flow rate Q _B, consumers A, adjacent, the time t _A after you start using the loading element, such as a heat pump, sinusoidal pulsating component of period t Will be detected.

[0013] Here, even as the integrated flowmeter 165 of the consumer B has detected ripple component period t, because the pulsation component is vibrating symmetrically with respect to the instantaneous flow rate Q _B, continuous instantaneous flow If the instantaneous flow rate is continuously integrated together with the measurement, the obtained integrated flow rate is not affected by the pulsation component. However, when the instantaneous flow rate is measured intermittently at a fixed measurement interval, and the instantaneous flow rate is multiplied by the measurement interval to obtain the integrated flow rate, the pulsation component appears in the integrated flow rate value.

FIGS. 15 and 16 are explanatory diagrams for explaining a case where an incorrect flow rate is measured by the customer B due to the influence of the pulsation component. In these figures, the vertical axis of (A) represents the instantaneous flow rate, and the horizontal axis represents time. In these figures, the ordinate of (B) indicates the integrated flow rate, and the abscissa indicates the time. Further, in these figures, the consumer A uses a load element such as a heat pump, but the consumer B shows the value of the flow rate observed when the fluid 100 is not consumed at all.

FIG. 15A shows an integrated flow meter 1 of the customer B.
65 shows the change in the instantaneous flow observed at 65,
This instantaneous flow rate includes a pulsating component having a period t due to the influence of disturbance from the customer A. 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 position measured by the instantaneous flow sensor is indicated by a circle. Also, in this figure, the driving cycle T of the instantaneous flow sensor is twice the cycle t of the pulsating component, that is, T = 2t, and the time of each drive timing related to the intermittent driving of the instantaneous flow sensor is positive for the pulsating component. The _timing is synchronized with the peak time on the side (time t _B10 , t _B11 ,...). In this case, the instantaneous flow rate of the customer B, which should be zero, is always measured as the positive flow rate _QB10 .

FIG. 15B shows a case where the instantaneous flow rate sensor is driven in a state as shown in FIG.
The value of the integrated flow rate measured by the integrated flow meter 165 of the customer B is shown. The integrated flow rate of the customer B is calculated at time t
_{After B10} , V _B10 = Q _B10 × T, V _B11 = V _B10 + Q
_B10 × T, ... As described above, in the customer B, although the gas is not used, the instantaneous flow rate Q
_The flow rate is accumulated as if _B1 was used continuously.

In FIG. 16A, the driving period T of the instantaneous flow sensor is twice the period t of the pulsating component, that is, T = 2t, and the time of each driving timing relating to the intermittent driving of the instantaneous flow sensor is The figure shows a case where the pulsation component is synchronized with the negative peak time (time t _B20 , t _B21 ,...). In this case, the instantaneous flow rate of the customer B, which should be zero, is always measured as the negative flow rate _QB10 . FIG. 16B shows a case where the instantaneous flow rate sensor is driven in such a state, and
5 shows the value of the integrated flow rate measured at 5. The accumulated flow rate of the customer B is V _B20 = Q _B20 × after time t _B20.
T, V _B21 = V _B20 + Q _B20 × T,...
In this case, the integrating flow meter 165 of the consumer B is set to the time t
_{After B20} , the value is integrated on the negative side, indicating an incorrect integrated value.

As described above, when an attempt is made to reduce the power consumption of the flow meter by intermittently driving the instantaneous flow rate sensor, a measurement error occurs when the fluid flow contains a pulsation component due to disturbance. May occur.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a flow meter and a gas meter that can reduce power consumption without deteriorating measurement accuracy.

[0020]

According to the present invention, there is provided a flow meter which is intermittently driven at different time intervals according to the flow rate of a fluid passing through a flow path, and has a signal corresponding to a flow rate per unit time. And an integrated flow rate calculating means for calculating an integrated flow rate of the fluid based on an output signal from the instantaneous flow rate detecting means.

In this flow meter, a signal corresponding to the flow rate per unit time is output from the instantaneous flow rate detecting means which is intermittently driven at different time intervals according to the flow rate of the fluid passing through the flow path. Further, the integrated flow rate of the fluid is calculated by the integrated flow rate calculating means based on the output signal from the instantaneous flow rate detecting means.

According to a second aspect of the present invention, there is provided a flow meter according to the first aspect, wherein the instantaneous flow rate detecting means is arranged such that when the flow rate of the fluid is in the small flow rate range, it is greater than when the flow rate is in the large flow rate range. It is designed to be driven at short time intervals.

In this flow meter, when the flow rate of the fluid is in a small flow rate range which is easily affected by pulsation, the instantaneous flow rate detection means is driven at shorter time intervals than when the flow rate is in a large flow rate range. .

According to a third aspect of the present invention, in the flow meter according to the first aspect, when the instantaneous flow rate detecting means is driven at random time intervals and the flow rate of the fluid is in a small flow rate range, The drive is performed at shorter time intervals than when the flow rate is in the large flow rate range.

In this flow meter, the instantaneous flow rate detecting means is driven at random time intervals, and measurement errors due to pulsation are reduced. In addition, 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 unit is driven at shorter time intervals than when the flow rate is in a large flow rate range.

According to a fourth aspect of the present invention, the gas meter is intermittently driven at different time intervals according to the flow rate of the gas passing through the flow path and outputs a signal corresponding to the flow rate per unit time. And integrated flow rate calculating means for calculating the integrated flow rate of gas based on the output signal from the instantaneous flow rate detecting means.

In this gas meter, a signal corresponding to the flow rate per unit time is output from the instantaneous flow rate detection means which 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 of the gas is calculated by the integrated flow rate calculating means based on the output signal from the instantaneous flow rate detecting means.

[0028]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a configuration diagram schematically showing a flow meter according to an embodiment of the present invention. The flow meter shown in this figure is
This is for obtaining an 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 sensor 20 attached to the pipe 1, a control unit 21 connected to the instant flow sensor 20, and a display unit 22 connected to the control unit 21. I have. In addition, the instantaneous flow rate sensor 20
The control unit 21 corresponds to the “integrated flow rate calculating unit” in the present invention.

In this flow meter, the instantaneous flow sensor 20 is intermittently driven at time intervals corresponding to the flow rate, and outputs a signal corresponding to the flow rate of the fluid 2 flowing through the pipe 1 per unit time. I have. 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 intermittently integrates the instantaneous flow rate to calculate the integrated flow rate. Has become. The integrated flow rate calculated by the control unit 21 is displayed on the display unit 2
2 is displayed. The drive timing of the instantaneous flow sensor 20 will be described later in detail with reference to the drawings.

FIG. 2 is a block diagram showing an example of the instantaneous flow sensor 20. The flow sensor 20a shown in FIG. 1 is one of so-called thermal flow sensors, and includes a temperature sensor 3 arranged on the upstream side, a temperature sensor 5 arranged on the downstream side of the temperature sensor 3, It has a heater 4 provided between the temperature sensor 3 and the temperature sensor 5.
The 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 difference between the temperatures detected by the two temperature sensors 3 and 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 between the temperatures detected by the two temperature sensors 3 and 5. The temperature sensors 3 and 5 use, for example, the fact that the resistance value of a platinum thin film resistor changes with temperature.

FIG. 3 is a block diagram showing another example of the instantaneous flow sensor 20. The flow sensor shown in this figure is one of so-called ultrasonic flow sensors, and a pair of transceivers 31 and a pair of transmitters and receivers 31 arranged obliquely on the pipe wall of the pipe 1 with respect to the flow direction of the fluid 2. A transceiver 32 is provided. The transmitter / receiver 31 and the transmitter / receiver 32 are capable of transmitting ultrasonic waves to each other and receiving ultrasonic waves transmitted from the other. Here, the ultrasonic waves 33 transmitted from the transceiver 32 to the transceiver 31 include 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. Therefore, the ultrasonic waves 33 and 34
By the time it is received by the transceiver 31 and the transceiver 32,
A time difference corresponding to the flow rate of the fluid 2 will occur. Therefore, the flow rate corresponding to the flow velocity of the fluid 2 can be obtained based on the time difference.

Here, the instantaneous flow rate sensor 20 is not limited to the above-mentioned thermal flow rate sensor 20a or ultrasonic flow rate sensor, and a sensor having a different structure from these may be used. In the following, the instantaneous flow rate sensor 20
Is described as an example in the case of a thermal type flow sensor 20a.

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 has, as components of the control unit 21, a bridge circuit 6 connected to the temperature sensors 3 and 5 of the flow sensor 20a, and a bridge circuit 6 connected to the bridge circuit 6. Amplifier 7, the sampling circuit 8 connected to the amplifier 7, and the A connected to the sampling circuit 8.
/ D converter 9, a CPU (central processing unit) 10 connected to the A / D converter 9, and a flow sensor 20a.
A heater driving circuit 12 connected to the heater 4 and a timing circuit 13 connected to each of these components. The CPU 10 is connected to the display unit 22.
The flow meter according to the present embodiment has a battery 11 that supplies power Vcc to each component of the flow meter.

In the flow meter of the present embodiment, the heater 4
Is driven by the heater drive circuit 12 so that the fluid 2 near the heater 4 is heated so as to exhibit a constant temperature rise. The temperature of the fluid 2 near the heater 4 is detected by a temperature sensor 3 on the upstream side and a temperature sensor 5 on the downstream side.

A change in the resistance value of each 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 is
The signal is amplified by the signal S5 and input to the sampling circuit 8. The sampling circuit 8 uses the measurement timing signal S3 from the timing circuit 13 to
The output signal S5 of the amplifier 7 is sampled at predetermined intervals described later, and a signal S6 is output.

The output signal S6 of the sampling circuit 8 is A
The signal is converted into a digital signal S7 by the
The integrated value of the flow rate is input to the PU 10 so as to be obtained. The CPU 10 outputs a control signal S9 to the timing circuit 13 to control the drive timing of each unit. Further, the CPU 10 outputs a signal S8 corresponding to the obtained integrated value to the display unit 22 to display the integrated value of the flow rate on the display unit 22.

The timing circuit 13 outputs the heater drive signal S1 to the heater drive circuit 12 based on the control signal S9 from the CPU 10, and measures the bridge circuit 6, the amplifier 7, the sampling circuit 8 and the A / D converter 9. The measurement timing signal S3 is output to the system. In the flow meter of the present embodiment, the power supply Vcc is supplied to each unit by the battery 11, but as will be described in detail later, the drive timing of each unit is optimally controlled in accordance with the flow rate to reduce the power supply. It ensures both power consumption and measurement accuracy.

FIG. 5 is an explanatory diagram showing the drive timing of the flow sensor 20a in the present embodiment. In the figure, (A) shows the timing of the heater drive signal S1 output from the timing circuit 13 to the heater drive circuit 12. The heater drive circuit 12 supplies a drive current to the heater 4 in synchronization with the heater drive signal S1. (B) shows the temperature S2 near the heater 4;
It shows about the change. The temperature S2 near the heater 4 is:
At the same time as the heater driving signal S1 does not change for the thermal time constant, the rise time t _r (between times t ₂₀ ~ time t _21),
And fall time t _f (between time t ₂₄ and time t ₂₅ )
, Each has a time delay of several tens of ms.
(C) shows the timing circuit 13 to the sampling circuit 8.
5 shows the timing of the measurement timing signal S3 output to the measurement system. Measurement timing signal S3
During a period in which the temperature near the heater 4 is stable (time t ₂₁
And is output during) the to time t _24. Then, during the period of the measurement timing signal S3 (time t ₂₂
Instantaneous flow rate of the fluid 2 is measured during) the to time t _23.

Next, the operation of the flow meter having the above configuration will be described.

FIG. 6 is a flowchart for explaining the basic operation of the flow meter according to the present embodiment. In this embodiment, in order to reduce power consumption, the flow sensor 2
0a and the respective components for driving the flow sensor 20a operate intermittently. First, a basic flow of the intermittent operation will be described.

First, the CPU 10 starts the timing circuit 13 by transmitting the control signal S9 (step S11). Next, the timing circuit 13 outputs the heater drive signal S1 to the heater drive circuit 12, and starts heating the heater 4 of the flow rate sensor 20a (Step S1).
2). Here, as described above, it takes several tens of milliseconds for the temperature near the heater 4 to stabilize after the heating of the heater 4 is started.
It takes time.

Next, after a period in which the temperature in the vicinity of the heater 4 is considered to be stable, the timing circuit 13 supplies the bridge circuit 6, the amplifier 7, the sampling circuit 8 and the A / D converter 9 constituting the measuring system. The measurement timing signal S3 is transmitted, and the measurement system is started (Step S13). By the time the temperature in the vicinity of the heater 4 is stabilized, each circuit of the measurement system is also stabilized, and the measurement system acquires an output signal output from the flow sensor 20a as measurement data (step S14). When the measurement data is obtained in the measurement system, the CPU 10 immediately stops outputting the heater drive signal S1 to the heater drive circuit 12 and stops heating the heater 4 (step S15). The reason why the heating of the heater 4 is stopped immediately is that the heater 4 consumes the most power.

Next, the measurement data converted into the digital signal S7 in the A / D converter 9 is sent to the CPU 10 (step S16). As a result, one substantial measurement sequence ends, and each circuit of the measurement system stops (step S17), and the timing circuit 13 stops (step S18). In the CPU 10,
The instantaneous flow rate is calculated based on the measurement data, and a value obtained by multiplying the instantaneous flow rate by the drive interval of the flow rate sensor 20a is sequentially added to obtain an integrated flow rate. The integrated flow rate obtained by the CPU 10 is output to the display unit 22 and displayed.

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 drive interval of the flow sensor 20a is made different depending on the flow rate.

FIG. 7 is a flowchart for explaining the 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
The value of the obtained instantaneous flow rate is a predetermined value Q set in advance.
It is determined whether the value exceeds 1 (step S22). Here, when the flow meter is used as a general gas meter, for example, the predetermined value Q1 is set to about 300 l / h. However, the predetermined value Q1 is not limited to this value.

The CPU 10 determines that the value of the instantaneous flow rate is a predetermined value Q1.
If (Y), the start timing of the timing circuit 13 is controlled so that the drive interval of the flow rate sensor 20a becomes longer (step S23). Also, the CPU 10
If the value of the instantaneous flow rate does not exceed the predetermined value Q1 (N),
The activation timing of the timing circuit 13 is controlled so that the drive interval of the flow rate sensor 20a is shortened (step S2).
4). Thus, for example, in a large flow rate region, the drive interval of the flow rate sensor 20a becomes longer, and in a small flow rate range, the drive interval of the flow rate sensor 20a becomes shorter.

Next, the driving interval of the flow rate 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 figures, (A) is a diagram for explaining a drive interval in a small flow rate region, and (B) is a diagram for explaining a drive interval in a large flow rate region. In these figures, the positions where the flow rate is substantially measured by the flow rate sensor 20a are indicated by black circles.

FIG. 8 is a diagram for explaining a method of setting the drive interval of the flow rate sensor 20a applied when the flow of the fluid 2 has almost no pulsation component due to disturbance. In this case, the drive interval τ0 ′ in the large flow rate region (FIG. 8B) is longer than the drive interval τ0 of the flow sensor 20a in the small flow rate region (FIG. 8A). Thereby, the times of the respective drive timings related to the intermittent drive of the flow sensor 20a in the small flow rate region are the time t1,
t2, t3. . . Becomes The time of the drive timing of the flow rate sensor 20a in the large flow rate range is time t1 ',
t2 ', t3'. . . Becomes In addition, if the drive interval τ0 in the small flow rate region is lengthened, the period in which the flow rate sensor 20a is intermittently driven is lengthened and the power consumption is greatly reduced, but the measurement accuracy is also lowered. Determined to a degree. In addition, the driving interval τ in the large flow rate region
0 'is set, for example, to a value that is about twice the drive interval τ0.

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 does not change with the flow rate. Therefore, as the flow rate increases, the rate of influence of the pulsation on the measurement accuracy decreases relatively. For this reason, in the large flow rate region, the measurement accuracy does not deteriorate even if the drive interval of the flow rate sensor 20a is increased. Further, by setting the drive interval τ0 ′ in the large flow rate region to be long, power consumption can be suppressed low.

FIG. 9 shows a flow rate sensor 20a applied when there is a pulsation component large enough to affect the measurement of the flow rate.
This is for describing an example of a method of setting the drive interval. In this example, the drive timing of the flow rate sensor 20a is changed at random so that the pulsation component does not affect the integrated flow rate value. That is, in this example, a constant basic driving interval τa (τ
a ') is set, and the drive timing is randomly varied within the basic drive 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 sensor 20a in the small flow rate region (FIG. 9A).

Here, the start time t of the basic drive interval τa
1, t2, t3. . . (T1 ', t2', t
3 '. . . ) To the driving timings ta, tb, t
c. . . Assuming that the time until (ta ', tb', tc '...) is τn, then τn = rnd (n) × τa. Here, n is an integer of 1 or more, and rnd (n) is 0
This is the n-th random number less than or equal to one. Thereby, the time of each drive timing relating to the intermittent drive of the flow sensor 20a becomes random, and the influence of the pulsation component on the integrated flow value is prevented.

FIG. 10 shows a flow rate sensor 20 applied when there is a pulsation component large enough to affect the measurement of the flow rate.
This is for explaining another example of the setting method of the drive interval of a. In this example, the pulsation component affects the integrated flow value by randomly varying the drive interval of the flow rate sensor 20a without setting the basic drive interval τa (τa ′) as in the case of FIG. I try not to.
In this case, in the large flow rate region (FIG. 10B), the driving intervals τ1 ′, τ2 ′, τ3 ′,. . . Are the drive intervals τ1, τ2, τ3,... Of the flow rate sensor 20a in the small flow rate range (FIG. 10A). . . Longer than it is. Thereby, the times of the respective drive timings related to the intermittent drive of the flow sensor 20a in the small flow rate region are the time t1,
t2, t3. . . Becomes The time of the drive timing of the flow rate sensor 20a in the large flow rate range is time t1 ',
t2 ', t3'. . . Becomes

In this example, assuming that 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). Note that tmin is determined by the limitation of the power consumption and the response time of the flow rate sensor.
One second. Further, tmax is determined by the required measurement accuracy, and is about 1 to 3 seconds in the present embodiment.

In the above description, three methods shown in FIGS. 8 to 10 have been described as the method of setting the movement interval. However, in practice, it is assumed that whether or not there is a pulsation component in the measurement environment is known in advance. Sets the drive interval by any one method suitable for the environment. In addition, one flow meter may use a plurality of drive interval setting methods depending on whether or not there is a pulsating component. 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 relatively small intervals and making a determination based on this.

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 instantaneous flow rate sensor 20 Since the integrated flow rate is calculated based on the output signal, the power consumption can be reduced without deteriorating the measurement accuracy.

The present invention is not limited to the above embodiment, but can be variously modified. For example, in the above-described embodiment, the drive interval is made different in the case of the large flow rate and the case of the small flow rate. However, the drive interval may be made different in three or more stages.

[0058]

As described above, claims 1 to 3 are described.
According to the flow meter described in any one of the above or the gas meter described in the fourth aspect, the integrated flow rate is calculated based on the output signal from the instantaneous flow rate detection means which is intermittently driven at different time intervals according to the flow rate. As a result, power consumption can be reduced without deteriorating measurement accuracy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a flow meter according to an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating an example of an instantaneous flow rate sensor in the flow meter illustrated in FIG.

FIG. 3 is a configuration diagram illustrating another example of the instantaneous flow rate sensor in the flow meter illustrated in FIG.

FIG. 4 is a block diagram showing a detailed circuit configuration of the flow meter shown in FIG.

FIG. 5 is an explanatory diagram showing drive timings of the flow rate sensor shown in FIG.

FIG. 6 is a flowchart for explaining a basic operation of the flow meter according to the present embodiment.

FIG. 7 is a flowchart for explaining setting of a drive interval of the instantaneous flow rate sensor in the present embodiment.

FIG. 8 is an explanatory diagram showing an example of setting of a drive interval of the instantaneous flow rate sensor in the present embodiment.

FIG. 9 is an explanatory diagram showing another example of setting of the driving interval of the instantaneous flow rate sensor in the present embodiment.

FIG. 10 is an explanatory view showing another example of a plate for setting the driving interval of the instantaneous flow rate sensor in the present embodiment.

FIG. 11 is a configuration diagram schematically showing 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 continuously driven.

FIG. 13 is an explanatory diagram for describing a pulsation component due to disturbance.

FIG. 14 is another explanatory diagram for describing a pulsation component due to disturbance.

FIG. 15 is an explanatory diagram for describing a measurement error generated in a conventional flow meter.

FIG. 16 is another explanatory diagram for describing a measurement error generated in a conventional flow meter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pipe, 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.

Continued on the front page F term (reference) 2F030 CA03 CA10 CC13 CD13 CE02 CE04 CE07 CE25 2F035 DA14 EA04 5G065 AA01 EA02 FA05 GA06 JA07 KA02 KA05 LA07

Claims (4)

[Claims] 1. An instantaneous flow rate detecting means which is intermittently driven at different time intervals according to a flow rate of a fluid passing through a flow path and outputs a signal corresponding to a flow rate per unit time, and said instantaneous flow rate detection. A flow rate calculating means for calculating an integrated flow rate of the fluid based on an output signal from the means. 2. The apparatus according to claim 1, wherein said instantaneous flow rate detection means is driven at shorter time intervals 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. Flowmeter as described. 3. The instantaneous flow rate detecting means is driven at random time intervals, and is driven at shorter time intervals when the fluid flow rate is in a small flow rate range than when the fluid flow rate is in a large flow rate range. The flowmeter according to claim 1, wherein the flow rate is measured. 4. An instantaneous flow rate detecting means which is intermittently driven at different time intervals according to a flow rate of a gas passing through the flow path and outputs a signal corresponding to a flow rate per unit time; A gas flow rate calculating means for calculating an integrated flow rate of the gas based on an output signal from the means.