JP4734822B2 - Flow measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow rate measuring device for measuring a flow rate of gas or the like.
[0002]
[Prior art]
As shown in FIG. 6, the conventional flow measuring device of this type includes ultrasonic transmitters / receivers 2a and 2b in a part of the fluid conduit 1, starts flow measurement by a signal from the measurement start means 3, and The time measuring means 4 measures the propagation time from the transceivers 2a to 2b. When there is a periodic fluctuation in the flow, the flow rate measurement value varies depending on the measurement timing. For example, in a gas meter for measuring household gas consumption, pressure fluctuation occurs when a gas engine is operated nearby, and the flow rate fluctuates due to the fluctuation. FIG. 7 is a diagram showing the flow rate waveform at this time, and the flow rate indicated by A actually flows. Since digital measurement is intermittently sampled, values such as time t1 (flow rate Q1), time t2 (flow rate Q2), and time t3 (flow rate Q3) are obtained and averaged by the microcomputer to calculate the flow rate.
[0003]
Further, the presence or absence of pulsation is detected, and when there is a pulsating flow, measurement is frequently performed and the flow rate is calculated from the average value. In order to cope with various pulsation cycles, an increase in the number of data inputs / outputs and an accompanying increase in power consumption. In the case of an analog type, continuous signals from time t0 to t4 are averaged through an integrator.
[0004]
[Problems to be solved by the invention]
However, the conventional flow rate measuring device has the following problems. That is, since digital sampling is intermittent sampling, it takes a long time to obtain an accurate flow rate because it is necessary to increase the number of measurements and average the measured values. In addition, the processing of input / output data becomes complicated, and there is a tendency that not only time but also power consumption increases.For this reason, in a flow measuring device that also functions as a safety function such as shut-off during abnormal use such as a gas meter, It has been an issue to accurately measure the flow rate in a short time for battery-driven and safety.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, a flow rate measuring device according to the present invention includes a transmitter / receiver that transmits or receives a sound wave in a fluid, a repeating unit that performs transmission / reception operations between the transmitter / receiver a plurality of times, and a plurality of sound waves generated by the repeating unit A measurement control unit that implements a plurality of measurement sets with the propagation time measurement as one measurement set, and a flow rate calculation unit that calculates the flow rate by integrating the values of the respective sound wave propagation times, the measurement control unit determines the number of measurement sets. This is measured and adjusted, so that even if the flow is pulsating, the followability is good, and the average flow rate can be measured correctly even in the case of a stable steady flow.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The invention according to claim 1 is a time measuring means for measuring a sound wave propagation time between a transmitter and a receiver, a measurement control means for carrying out a plurality of measurement sets by using the sound wave propagation measurement as one measurement set, and ending from the measurement start of the measurement set. Phase delay means that can adjust the delay time provided in any of the above and a flow rate calculation means that calculates the flow rate by integrating the values of the respective sound wave propagation times, so that even if the timekeeping means has low resolution, Accurate flow resolution is obtained.
[0007]
According to the second aspect of the present invention, since the phase delay means can adjust the delay by the measurement set, the flow rate resolution can be improved, and the flow rate can be measured with low power consumption and high accuracy.
[0008]
According to the third aspect of the present invention, since the delay time of the phase delay means is ½ or less than the period of the reference clock of the time measuring means for measuring the sound wave propagation time, the flow rate resolution is reliably improved.
[0009]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0010]
Example 1
Embodiment 1 of the present invention will be described below with reference to the drawings. In FIG. 1, a transmitter / receiver 6 a that transmits ultrasonic waves and a transmitter / receiver 6 b that receives ultrasonic waves are arranged in the flow direction in the middle of the fluid conduit 5. 7 is a transmission circuit for the transmitter / receiver 6a, 8 is an amplifier circuit for the signal received by the transmitter / receiver 6b, and the amplified signal is compared with the reference signal by the comparison circuit 9, and a signal equal to or higher than the reference signal is detected. After the delay circuit 12 delays the signal by the repetition means 11 by the number of times set by the repetition number setting means 10, an ultrasonic signal is repeatedly transmitted by the trigger circuit 13. The time when the number of times set by the repetition number setting means 10 is repeated is obtained by the time measuring means 14, and the value is stored in the storage means 15 incorporated in the microcomputer. 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).
[0011]
Next, the transmission / reception of the transmitter / receiver 6a and the transmitter / receiver 6b is switched by the switching means 16, and an ultrasonic signal is transmitted from the transmitter / receiver 6b to the transmitter / receiver 6a, that is, from downstream to upstream (hereinafter referred to as downstream transmission). This transmission is repeated as described above, and the time is counted. From the time difference, the flow rate calculation means 17 determines the flow rate value 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 repetition number setting means 18a for setting the number of repetitions of the repetition means, and a measurement number means 18b for setting how many times this measurement set is measured with the measurement based on the repetition number as one measurement set. ing.
[0012]
Next, the measurement sampling method will be described. FIG. 2 shows the state of measurement sampling when there is a pulsation. During the time T1, the upstream transmission described above is repeated four times, and the propagation time is counted by the time measuring means 14 and stored in the storage means 15. The propagation time t1 is stored. These four measurements are taken as one measurement set.
[0013]
Next, the transmitter / receivers 6a and 6b are switched, and downstream transmission is performed four times during the time T2, and the propagation time t2 is stored. Further, after a predetermined time has elapsed, upstream transmission is performed during time T3 and downstream transmission is performed during time T4, and propagation times t3 and t4 are stored.
[0014]
In this way, the upstream transmission and the downstream transmission are intermittently performed as a pair, and in this embodiment, measurement is performed in a total of 80 measurement sets up to T80, and the propagation time is stored in the storage means 15, respectively. The data in the storage unit 15 is calculated by the flow rate calculation unit 17 to calculate the flow rate. In this calculation, for example, the sum total of upstream transmissions is calculated, the average value of propagation times per one time is calculated from the sum of the number of repetitions, and the average value of propagation times per one time of downstream transmission is calculated in the same manner. It can be calculated from the time difference of time or the difference of reciprocal time. The timing is adjusted by the measurement control means 18 so that the measurement intervals of T1, T2, T3, T4, T79, and T80 are uniform.
[0015]
FIG. 2 shows a case where the flow is changing, while FIG. 3 shows a case where the flow is small and stable, for example, when the flow is stopped. At this time, since a minute flow rate must be detected, 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 increased. In FIG. 3, the number of repetitions is 12 times as one measurement set, and the flow rate resolution is tripled compared to the case of 4 times. In this way, measurement is performed up to 10 measurement sets up to T10. In the case of 80 measurement sets with 4 repetitions as described above, the total propagation of sound waves is 320 times, and in the case of 26 measurement sets with 12 repetitions, the power consumption is 120.
[0016]
(Example 2)
FIG. 4 is a block diagram showing the time measuring means 14 according to the second embodiment of the present invention. The time measuring means 14 includes a reference clock 14a such as a crystal oscillator, an upstream counter 14b, and a downstream counter 14c. The upstream counter 14b is for measuring the propagation time in upstream transmission. When the switching means 16 is switched, the reference clock 14a is connected to the upstream counter 14b, the count is started at the start of measurement, and a predetermined repetition is performed. When finished, the count stops.
[0017]
Next, when switching to downstream transmission is performed by the switching means 16, the reference clock 14a is switched to the downstream counter 14c side.
[0018]
At this time, the value of the upstream counter holds the stopped value. As described above, downstream transmission / reception is performed a predetermined number of times, and the downstream counter counts and stops. Next, the transmitter / receiver 16a and 16b are switched to upstream transmission again by the switching means 16, the reference clock 14a is connected to the upstream counter side, and the upstream counter continues to count the accumulated counter value from the previous counter value at the start of transmission. Count. Thereafter, this operation is repeated, and the counter values are accumulated 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 respectively read into the storage means 15 and converted into flow rate values by the flow rate calculation means 17.
[0019]
(Example 3)
FIG. 5 is a block diagram showing a main part of the third embodiment of the present invention. After the repeated transmission is completed, the signal passes through the phase delay means 19. That is, the counter stops with a delay of this delay time. This delay time can be adjusted in units of Tc / n (n is an integer) where one period of the reference clock 14a is Tc, and can be changed by the delay setting means 20 for each measurement set.
[0020]
Next, the operation of the phase delay means 19 will be described. First, the delay time Td1 = 0 is set when upstream transmission is performed in the first measurement set, and Td2 = 0 is similarly set for downstream transmission in the second measurement set. Next, in the third measurement set (upstream transmission), the delay time Td3 = Tc / n is set, and the fourth measurement set (downstream transmission) is similarly Td4 = Tc / n. 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 after 2 * N times, the initial value becomes zero.
[0021]
As a result, even a slight change in the propagation time appears as a difference in the counter value, and a minute propagation time difference equal to or less than the reference clock period can be detected, so that a minute flow rate is measured. Theoretically, a resolution equivalent to 1 / N of the reference clock period 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.
[0022]
Note that the position of the delay time may be set 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 very small. However, since it is a known value, it can be corrected in the flow rate calculation if necessary.
[0023]
【The invention's effect】
As described above, according to the first and second aspects of the present invention, the average flow rate can be measured with high accuracy regardless of the steady flow or the pulsating flow. Further, according to the third to eighth aspects of the present invention, the pulsating flow can be accurately measured without increasing the power consumption.
[Brief description of the drawings]
FIG. 1 is a block diagram of a flow rate measuring device according to a first embodiment of the present invention. FIG. 2 is a flow waveform diagram of the same device. FIG. 3 is another flow rate waveform diagram of the same device. Fig. 5 is a block diagram of the main part of the flow measuring device according to the third embodiment of the present invention. Fig. 6 is a block diagram of the conventional flow measuring device. Fig. 7 is a flow waveform diagram of the device. Explanation of symbols]
5 Fluid pipelines 6a, 6b Transceiver (first transceiver, second transceiver)
10 repeat count setting means 11 repeat means 14 timing means 14a reference clock 14b upstream counter 14c downstream counter 15 switching means 17 flow rate calculation means 18 measurement control means 19 phase delay means

Claims (3)

A transmitter / receiver that transmits or receives a sound wave in a fluid, a time measuring unit that measures a sound wave propagation time between the transmitter / receiver, and a measurement control unit that performs a plurality of measurement sets by using the sound wave propagation measurement as one measurement set; , A flow rate measurement unit provided with a phase delay unit for adjusting a delay time provided anywhere from the measurement start to the end of the measurement set, and a flow rate calculation unit for calculating the flow rate by integrating the values of the respective sound wave propagation times apparatus. The flow rate measuring device according to claim 1, wherein the phase delay means adjusts the delay time according to the measurement set. 2. The flow rate measuring device according to claim 1, wherein the delay time of the phase delay means is a value that is ½ or less than the period of the reference clock of the time measuring means for measuring the sound wave propagation time.

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