JP3443657B2 - Flow measurement device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring device for measuring the flow rate of gas or the like.

[0002]

2. Description of the Related Art As shown in FIG. 6, a conventional flow rate measuring device of this type has an ultrasonic transmitter / receiver 2a in a part of a fluid conduit 1.
2b is provided, the flow rate measurement is started by the signal of the measurement starting means 3, and the propagation time from the ultrasonic transceivers 2a to 2b is measured by the time measuring means 4. When the flow has a periodic fluctuation, the flow rate measurement value varies depending on the measurement timing. For example, in a gas meter that measures the amount of gas consumed by a household, pressure fluctuations occur when a gas engine is operated nearby, and the flow rate fluctuates due to the pressure fluctuations. FIG. 7 is a diagram showing the waveform of the flow rate at this time, and the flow rate indicated by A actually flows. Since sampling is performed intermittently in digital measurement, time t1 (flow rate Q1), time t2 (flow rate Q
2), a value such as time t3 (flow rate Q3) was obtained, and averaged by the microcomputer to calculate the flow rate.

Further, the presence or absence of pulsation is detected, and if there is a pulsating flow, measurement is frequently performed and the flow rate is calculated from the average value. In order to deal with various pulsation cycles, the number of data inputs and outputs is increased, and in the case of the analog type, continuous signals from time t0 to t4 are averaged through an integrator.

[0004]

However, the conventional flow rate measuring device has the following problems. That is, since the digital method is intermittent sampling, a long time is required because it is necessary to increase the number of times of measurement and average the measured values in order to obtain an accurate flow rate. In addition, the processing of input / output data becomes complicated, and not only time but also power consumption tends to increase. Therefore, in a flow rate measuring device that also has a security function such as interruption during abnormal use like a gas meter, It has been an issue to accurately measure the flow rate in a short time for battery-powered and safety reasons.

[0005]

In order to solve the above-mentioned problems, a flow rate measuring device of the present invention comprises a transmitter / receiver for transmitting or receiving a sound wave in a fluid, and a repeating means for performing a transmitting / receiving operation between the transmitter / receiver a plurality of times. And measurement control means for implementing a plurality of measurement sets with one measurement set of measurement of the sound wave propagation time by the repeating means, and flow rate calculation means for integrating the values of the respective sound wave propagation times to calculate the flow rate, The measurement control means measures by adjusting the number of times of the measurement set. With this, the followability is good even when the flow is pulsating, and the average flow rate can be correctly measured even in the case of a stable steady flow.

[0006]

A first aspect of the present invention is a transmitter / receiver for transmitting or receiving a sound wave in a fluid, a repeating means for transmitting / receiving a plurality of times between the transmitter / receiver, and a plurality of sound waves by the repeating means. includes a measurement control means for performing a plurality of measurement sets the measurement of the propagation time as a measurement set, the flow rate calculation means for calculating an integrated flow rate value of the each sound wave propagation time, the measurement control means, within a predetermined time In total
Depending on the number of measurement sets, multiple measurement sets within a predetermined time
By evenly allocating and measuring, the flow rate can be measured evenly in time, and the average flow rate can be measured with high accuracy regardless of the presence or absence of pulsating flow.

According to a second aspect of the invention, the value of the flow rate calculation means
Change the number of repetitions to adjust to the required flow resolution.
The number of repetitions can be changed to reduce the flow rate accuracy.
It can reduce power consumption.

According to the third aspect of the invention, from the upstream to the downstream
Separate propagation time and propagation time from downstream to upstream
Since it is equipped with a clocking means that directly adds to the
It is possible to perform integration without intervention, and the flow rate calculation is a simple process.
It can be done and low power consumption can be achieved.

According to a fourth aspect of the invention, the timing means is upstream.
Upstream counter that integrates the propagation time from the
Consists of a downstream counter that integrates the propagation time from the upstream to the upstream
And is switched in synchronization with the signal of the switching means,
Low power consumption due to automatic integration and easy processing
Can be reduced.

[0010]

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

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a transmitter / receiver 6 a for transmitting ultrasonic waves and a transmitter / receiver 6 b for receiving ultrasonic waves are arranged in the flow direction in the middle of the fluid conduit 5. Reference numeral 7 is a transmitter circuit to the transmitter / receiver 6a, 8 is an amplifier circuit for a signal received by the transmitter / receiver 6b, and the amplified signal is compared with a reference signal by a comparison circuit 9, and when a signal higher than the reference signal is detected. After the signal is delayed by the delay circuit 12 by the repeater 11 by the number of times set by the repeat count setting means 18a , the trigger circuit 13 repeatedly transmits the ultrasonic signal. The time when the number of times set by the number-of-repetitions setting means 10 is repeated is obtained by the time-measuring means 14, and the storage means 1 built in the microcomputer.
The value is stored in 5. In this way, ultrasonic waves are transmitted from the transceiver 6a to the transceiver 6b, that is, from upstream to downstream (hereinafter referred to as upstream transmission).

Next, the switching means 16 switches the transmission / reception of the transmitter / receiver 6a and the transmitter / receiver 6b to transmit an ultrasonic signal from the transmitter / receiver 6b to the transmitter / receiver 6a, that is, from downstream to upstream (hereinafter referred to as downstream transmission). Make a call, repeat this call as described above, and measure the time. Then, the flow rate calculation means 17 determines the flow rate value from the time difference in consideration of the size of the pipeline and the flow state. Reference numeral 18 denotes a measurement control means, which is composed of a repeat count setting means 18a for setting the repeat count of the repeat means and a measurement count means 18b for setting how many times this measurement set is measured with one measurement set for measurement by the repeat count. ing.

Next, a sampling method for measurement will be described. FIG. 2 shows a state of measurement sampling when there is a pulsation. During the time T1, the above-mentioned upstream transmission is repeated 4 times, and its propagation time is counted by the clock means 14 and stored in the storage means 15. The propagation time t1 is stored. These four measurements are taken as one measurement set.

Next, the transmitters / receivers 6a and 6b are switched to perform the downstream transmission four times during the time T2, and the propagation time t2 thereof is stored. Further, after a predetermined time has elapsed, upstream transmission is performed during time T3, and downstream transmission is performed during time T4.
3 and t4 are stored respectively.

As described above, the upstream transmission and the downstream transmission are intermittently performed in a pair, and in the present embodiment, measurement is performed by a total of 80 measurement sets up to T80, and the propagation time thereof is stored in the storage means 15, respectively. Then, the data in the storage means 15 is calculated by the flow rate calculation means 17 to calculate the flow rate. In this calculation, for example, the total sum of upstream transmissions is calculated, the average value of the propagation time per transmission is calculated from the total number of repetitions, and the average value of the propagation time per downstream transmission is calculated in the same manner, and each propagation is calculated. It can be calculated from the time difference of time or the difference of reciprocal of time. T1 / T2 and T3 / T4 and T79 / T8
The timing is adjusted by the measurement control means 18 so that the respective measurement intervals of 0 are uniform.

FIG. 2 shows the case where the flow is changing,
FIG. 3 shows a case where the flow is small and stable, for example, when the flow is stopped. At this time, a minute flow rate must be detected, so that high resolution is required for flow rate detection. By increasing the number of repetitions, a minute propagation time difference can be integrated and the flow rate resolution can be improved. In FIG. 3, the number of repetitions is 12 and one measurement set is used.
The flow rate resolution is three times higher than that of the first time. In this way, up to T10, 10 measurement sets are measured. The total number of sound wave propagations is 320 times in the case of 80 measurement sets with the number of repetitions of 4 times, and 120 times in the case of 26 measurement sets with the number of repetitions of 12 times, and the power consumption can be reduced.

(Embodiment 2) FIG. 4 is a block diagram showing a clock means 14 according to a second embodiment of the present invention. The clock means 14 includes a reference clock 14a such as a crystal oscillator, an upstream counter 14b and a downstream counter 14c. is there. The upstream counter 14b is for measuring the propagation time in upstream transmission, and when the switching means 16 is switched, the reference clock 14a is connected to the upstream counter 14b, counting is started at the start of measurement, and a predetermined repetition is performed. When it finishes, counting stops.

Next, when the switching means 16 switches to the downstream transmission, the reference clock 14a becomes the downstream counter 14a.
It is switched to the c side.

At this time, the value of the upstream counter holds the stopped value. Similar to the above, the transmission / reception on the downstream side is performed a predetermined number of times, and the downstream counter counts and stops. Next, the transmitter / receivers 16a and 16b are switched to the upstream transmission again by the switching means 16, the reference clock 14a is connected to the upstream counter side, and when the transmission is started, the upstream counter continues the accumulated counter value from the previous counter value. To count. Thereafter, this operation is repeated, and the counter values are integrated until the measurement of the number of measurement sets set by the measurement number means 18a is completed. The integrated values of the upstream and downstream counters are read into the storage means 15 and converted into flow rate values by the flow rate calculation means 17.

(Embodiment 3) FIG. 5 is a block diagram showing the essential parts of Embodiment 3 of the present invention. After the repeated transmission is completed, it passes through the phase delay means 19. That is, the counter stops after a delay of this delay time. This delay time can be adjusted in units of Tc / n (n is an integer) when one cycle of the reference clock 14a is Tc, and can be changed by the delay setting means 20 for each measurement set.

Next, the operation of the phase delay means 19 will be described. First, when the upstream transmission is performed in the first measurement set, the delay time Td1 = 0 is set, and in the downstream transmission in the second measurement set, Td2 = 0 is similarly set. Next, in the third measurement set (upstream transmission), the delay time Td3 = Tc
/ N, and Td4 = Tc / n in the fourth measurement set (downstream transmission) as well. In the fifth and sixth measurement sets, the delay time Td5 = Td6 = 2 * Tc / n is set, and thereafter the delay time increases by Tc / n. And 2
* After N times, the initial value becomes zero.

As a result, even a slight change in the propagation time will appear as a difference in the counter value, and a minute difference in the propagation time less than the cycle of the reference clock can be detected. To be done. Theoretically, a resolution equivalent to that when the cycle of the reference clock is set to 1 / N can be obtained.
The switching of the delay time is achieved by switching the tap of the delay line element or switching the digital circuit gate delay.

The position of the delay time may be placed at any position from the start to the stop of the measurement set. Since this delay time is a small value, the influence of the propagation time on the absolute value is extremely small, but since it is a known value, it can be corrected when calculating the flow rate if necessary.

[0024]

As described above, according to the present invention, the average flow rate can be measured with high accuracy regardless of the steady flow or the pulsating flow. Moreover, the pulsating flow can be accurately measured without increasing the power consumption.

[Brief description of drawings]

FIG. 1 is a block diagram of a flow rate measuring device according to a first embodiment of the present invention.

[Fig. 2] Flow rate waveform diagram of the device

FIG. 3 is another flow rate waveform diagram of the same device.

FIG. 4 is a block diagram of a main part of a flow rate measuring device according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a main part of a flow rate measuring device according to a third embodiment of the present invention.

FIG. 6 is a block diagram of a conventional flow rate measuring device.

FIG. 7 is a flow rate waveform diagram of the device.

[Explanation of symbols]

5 Fluid Pipelines 6a, 6b Transceiver (First Transceiver, Second Transceiver) 11 Repeating Means 14 Clocking Means 14a Reference Clock 14b Upstream Counter 14c Downstream Counter 15 Switching Means 17 Flow Rate Calculating Means 18 Measurement Control Means 18a Repeat Count Setting Means 19 Phase delay means

Claims (4)

(57) [Claims] 1. A transmitter / receiver for transmitting or receiving a sound wave in a fluid, a repeating unit for transmitting / receiving between the transmitters / receivers a plurality of times, and a plurality of times for measuring the sound wave propagation time by the repeating unit as one measurement set. Measurement control means for implementing the measurement set, and flow rate calculation means for calculating the flow rate by integrating the values of the respective sound wave propagation times, and the measurement control means determines the predetermined number of times within a predetermined time period. Time
Almost evenly allocate multiple measurement sets in the space
That the flow rate measuring device. 2. The number of repetitions depending on the value of the flow rate calculation means
The flow rate measuring device according to claim 1, wherein 3. Propagation time from upstream to downstream and from downstream to above
A timer that directly integrates the propagation time to the flow separately
And a flow rate calculator that calculates the flow rate from the value of the timing means.
The flow rate measuring device according to claim 1, further comprising a step . 4. The time measuring means is a propagation time from upstream to downstream.
Upstream counter that accumulates and the propagation time from downstream to upstream
Is composed of a downstream counter that integrates
The flow rate measuring device according to claim 3, which is switched in synchronization with the flow rate measuring device.