JPH1144563A - Apparatus for measuring flow rate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a correct average flow rate in a short time even when a fluctuating flow is present, by providing a fluctuation detection means and a pulsation detection means, and calculating a flow rate from a propagation time difference in the neighborhood of an average flow rate of a fluctuation waveform. SOLUTION: When a flow rate value of a fluid conduit fluctuates periodically, a fluctuation waveform is detected by a fluctuation detection means 16 and a measurement start signal is output from a measurement start means 18. A pulsation detection means 17 detects when an a.c. component of the waveform reaches the vicinity of zero, and a trigger means 10 starts to transmit ultrasonic waves from a first transmitter-receiver 7A. A second transmitter-receiver 7B obtains a signal, and a timer means 13 measures a propagation time and takes the data into a controller such as a microcomputer or the like, whereby a switching means 14 switches reception and transmission. The transmission is started when the a.c. component of the waveform signal from the fluctuation detection means 16 becomes nearly zero again. The propagation time at the time is measured in the same manner by the timer means 13. A flow rate is obtained by a signal-processing means 15 from a difference of the two propagation times.

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 a flow rate of gas or the like.

[0002]

2. Description of the Related Art A conventional flow measuring device of this type will be described with reference to FIGS. In the figure, a flow detecting means 2 such as a thermal flow sensor is provided in a part of a fluid pipeline 1, and an output signal of the flow detecting means 2 is amplified or digitized by a signal processing means 3. When there is a periodic fluctuation in the flow, the measured flow rate varies depending on the timing of the measurement. For example, in a gas meter for measuring household gas consumption, a pressure fluctuation occurs when a gas engine is operated nearby. For this reason, not only a device for buffering pressure fluctuations is provided, but if there is a fluctuation in the flow rate, the signal is averaged by the averaging means 4 and the average flow rate is calculated by the flow rate calculating means 5. FIG. 8 is a diagram showing a waveform of the flow rate at this time, and the flow rate indicated by A is actually flowing. In digital measurement, sampling is performed intermittently, so that time t1 (flow rate Q
Values such as 1), time t2 (flow rate Q2), and time t3 (flow rate Q3) are obtained, and the microcomputer averages the flow rate. In the case of the analog type, a signal continuous from time t0 to time t4 is averaged via an integrator.

[0003]

However, the conventional flow rate measuring device has the following problems. In other words, the digital type is intermittent sampling, and it takes a long time to obtain the accurate flow rate because it is necessary to increase the number of measurements and average the measured values.In the analog type, continuous measurement is required. Power consumption was large. In addition, it is conceivable to set a measuring time equal to an integral multiple of the changing period and obtain a measuring period. However, in the case of a pulsating flow having a changing period, it is necessary to obtain a period for each measurement, so that the measuring time becomes longer. For this reason, it has been an issue to measure the flow rate accurately in a short time for battery operation and safety in a flow rate measuring device such as a gas meter which also has a safety function such as shutting off when abnormal use is performed. .

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a flow rate detecting means for detecting a flow rate of a fluid, a fluctuation detecting means for detecting a fluctuation waveform of the fluid, and a measurement of the flow rate detecting means. A pulsation measuring means which starts near zero of an AC component of the fluctuation waveform; and a flow rate calculating means for processing a signal of the flow rate detecting means. According to the above invention, the flow rate is calculated by measuring near the zero of the alternating current component of the flow which fluctuates, and an accurate average flow rate is obtained in a short time.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a flow rate detecting means for detecting a flow rate of a fluid, a fluctuation detecting means for detecting a fluctuation waveform of the fluid, and a measurement of the flow rate detecting means, which is performed near the zero of an AC component of the fluctuation waveform. And a flow rate calculating means for processing a signal of the flow rate detecting means. And since the flow rate around the average of the fluctuation waveform is measured,
An accurate average flow rate can be obtained in a short time.

Also, a flow rate detecting means for calculating a flow rate based on an ultrasonic propagation time difference between a transmitter and a receiver for transmitting or receiving an ultrasonic wave in a fluid, a fluctuation detecting means for detecting a fluctuation waveform of the fluid, A pulsation measuring means for starting the measurement near zero of the AC component of the fluctuation waveform, and a flow rate calculating means for processing a signal of the flow rate detecting means. Since the flow rate is measured from the propagation time difference at the flow rate near the average of the fluctuation waveform, an accurate average flow rate can be obtained in a short time.

Further, the fluctuation detecting means is constituted by pressure detecting means for detecting a pressure in the fluid. By detecting the flow rate fluctuation by the pressure fluctuation, the fluctuation waveform can be easily detected.

Further, the fluctuation detecting means is activated based on the measured value of the flow detecting means. Since the fluctuation detecting means is operated only when there is fluctuation, power consumption can be reduced.

When the AC component value of the fluctuation detecting means is equal to or larger than a predetermined value, the fluctuation is measured by the pulsation detecting means. Only when the fluctuation is large, the measurement is performed by the pulsation detecting means, and when the pulsation is small, the measurement can be performed for a shorter time than usual.

Further, the apparatus is provided with an increase / decrease detecting means for judging a direction in which the flow rate increases / decreases. Then, since the flow rate is calculated from the average of the flow rate value that started measurement near zero when the flow rate increased and the flow value started measurement near zero when the flow rate decreased, there is little error even if the measurement time is long. Average flow rate can be measured.

Further, the apparatus further comprises an increase / decrease detecting means for judging a direction in which the flow rate increases / decreases, and a switching means for changing the transmission direction of the transceiver. Then, measurement near zero when the flow rate increases and measurement near zero when the flow rate decreases after the switching means is operated, and the flow rate is calculated from the propagation time difference, the measurement of the propagation time by the ultrasonic wave becomes longer. The average flow rate with little error can be measured.

Further, a flow rate detecting means for detecting a flow rate of the fluid, a fluctuation detecting means for detecting a fluctuation waveform of the fluid, a cycle detecting means for obtaining a fluctuation cycle from the fluctuation means, A pulsation measuring means for starting the measurement of the flow detecting means before a predetermined time and ending the measurement after the predetermined time from zero, and a flow calculating means for processing a signal of the flow detecting means. Then, since the flow rate before and after the fluctuation waveform is centered at zero, an accurate average flow rate can be measured in a short time.

[0013]

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

(Embodiment 1) FIG. 1 is a block diagram showing a flow rate measuring apparatus according to Embodiment 1 of the present invention. In FIG.
A first transceiver 7A for transmitting ultrasonic waves and a second transceiver 7B for receiving ultrasonic waves as flow rate detecting means 7 are arranged in the flow direction in the fluid line 6 in the flow direction. 8 is a flow rate calculating means for processing and calculating the signal of the flow rate detecting means 7; 9 is a transmission circuit which drives the first transceiver 7A by the trigger means 10 and directs it toward the second transceiver 7B, that is, from upstream to downstream. Transmit ultrasound. The amplification circuit 11 amplifies the signal received by the second transceiver 7B, and the amplified signal is compared with the reference signal by the comparison circuit 12, and the time when a signal equal to or greater than the reference signal is detected is determined by a timer counter. It is determined by the appropriate timing means 13.

Next, the transmission / reception of the first transceiver 7A and the second transceiver 7B is switched by the switching means 14, and the second transceiver 7A is switched.
An ultrasonic signal is transmitted from B to the first transceiver 7A, that is, from the downstream to the upstream, and this transmission is repeated as described above, and the time is measured. Then, the flow rate value is obtained by the signal processing means 15 in consideration of the size of the pipeline and the flow state from the time difference. Fluid line 6 has fluctuation detecting means 16 for taking out the AC component of this signal through a capacitor, determining the AC component near zero by pulsation measuring means 17 having a zero-cross comparator, and adjusting the timing with measurement starting means 18. , The transmission of the ultrasonic wave by the trigger means 10 is started. Reference numeral 19 denotes an activation unit for starting and stopping the operation of the pulsation detection unit 16.

Next, the operation will be described. If the flow rate value of the fluid line 6 fluctuates periodically, the fluctuation detecting means 16
The pulsation measuring means 17 determines when the measurement start signal is output from the measurement start means 18 and the AC component of the waveform has reached near zero, and the trigger means 10 transmits the ultrasonic wave to the first transceiver. Transmission is started from 7A. A signal is obtained from the second transceiver 7B, the propagation time is measured by the time measuring means 13, and when data is taken in by a controller such as a microcomputer, transmission and reception are switched by the switching means 14. Then, transmission starts when the AC component of the waveform signal from the fluctuation detecting means 16 reaches near zero again. The propagation time at that time is similarly measured by the time measuring means 13 and the flow rate is obtained by the signal processing means 15 from the difference between the two propagation times.

FIG. 2 shows a fluctuation waveform of the flow rate.
Ultrasonic transmission from upstream to downstream is performed between 1 and t2. Then, the transmitter and the receiver are switched, and the zero-cross time is similarly captured, and the ultrasonic wave is transmitted from the downstream to the upstream during the time t3 to t4, and the propagation time difference is obtained. Value can be obtained.

The pulsation detecting means 16 detects a change in pressure by the pressure detecting means. The pulsation can be detected because the fluctuation of the pressure has a certain relationship with the fluctuation of the flow rate. The accuracy of the pressure detection can be further improved by detecting the pressure difference from two locations in the fluid line 6 having a pressure difference.

When there is no pulsation of the fluid, pulsation detection means 1
It is not necessary to perform the flow rate measurement according to 7, and the measurement may be started at a certain time interval. At this time, the pulsation detection means 16 does not need to perform measurement for pulsation measurement. As long as the pressure detecting means is used, it is sufficient to perform measurement at a relatively long time interval, such as normal pressure monitoring in the fluid pipeline 6. When pulsation occurs, the value of the signal processing means 15 of the flow rate calculating means 8 fluctuates in the flow rate measurement at regular time intervals. When the fluctuation value reaches a certain value or more, the pulsation detection means 16 is operated by the activation means 19 to perform the pulsation measurement as described above.

As described above, if the pulsation is small, it is not necessary to perform the measurement by the pulsation measuring means 17. Whether to perform pulsation measurement is determined by the level value of the fluctuation component of the pulsation detection means 16. This level can be determined by a comparator.

[0021] It is also possible to obtain higher accuracy by averaging several flow values. (Embodiment 2) FIG. 3 is a block diagram showing a flow rate measuring apparatus according to Embodiment 2 of the present invention. The difference from the first embodiment is that an increase / decrease detection means 20 for judging a method of pulsating flow rate change is provided. When the time for the flow rate measurement is required from t1 to t2 in the waveform of FIG. 2, the average flow rate from t1 to t2 is obtained, and similarly, the average flow rate from t3 to t4 is obtained. As a result, the error increases when the measurement time is long. The increase / decrease detection means 20 detects whether the flow rate has changed from a smaller one to a larger one or from a larger one to a smaller one. Then, as shown in FIG. 4, when the flow rate is increasing, the zero crossing (from time t1 to t
The average of the flow measurement started at 2) and the flow measurement started at the zero cross (from time t3 to t4) when the flow is decreasing is determined. In this way, even if the measurement time is long, they cancel each other out, so that the error becomes small. In this example, measurement is performed at t3, which is the next zero crossing after time t1, but if the cycle and magnitude of the pulsation are stable, measurement is started at time t6 with a delay of one or more cycles instead of time t3. Is also good.

In the ultrasonic flow rate measurement, the transmission from the upstream to the downstream of the flow and the transmission from the downstream to the upstream are switched by the switching means 14, and the flow rate is calculated from the propagation time difference. The transmission direction is switched after the measurement from time t1 in FIG. 4, and then the measurement is performed from time t3. If the flow rate is calculated from the propagation time length, the average flow rate is calculated.

(Embodiment 3) FIG. 5 is a block diagram of a flow rate measuring apparatus according to Embodiment 3 of the present invention. The difference from the first embodiment is that a period detecting unit 21 for calculating a period that fluctuates according to a signal from the fluctuation detecting unit 16 is provided, and measurement is started a predetermined time earlier than the zero cross. As shown in the fluctuation waveform of FIG. 6, since the period value is obtained by the period detecting means 21, the measurement is started at a time t 1 ′ which is a predetermined time earlier than the zero-cross time t 1, and is ended at the time t 2. If the predetermined time is set to 1/2 of the time required for measurement, the values of t1-t1 'and t2-t1 become equal, and the obtained flow value becomes the average thereof. If the average value of the fluctuating flow rate is obtained, an average value with a small error can be obtained even if the symmetry is somewhat impaired.

Although the embodiment has been described with reference to the case where the flow rate changes periodically, the present invention can be applied to a case where the cycle also changes.

[0025]

As is clear from the above description, the following effects can be obtained according to the flow rate measuring device of the present invention.

(1) Flow rate detecting means for detecting the flow rate of the fluid, fluctuation detecting means for detecting the fluctuation waveform of the fluid, and pulsation measuring means for starting the measurement of the flow rate detecting means near zero of the AC component of the fluctuation waveform. And a flow rate calculating means for processing the signal of the flow rate detecting means, and measures the flow rate around the average of the fluctuation waveform, so that an accurate average flow rate can be obtained in a short time even if there is a repetitive fluctuation flow.

(2) Flow rate detecting means for calculating a flow rate based on an ultrasonic wave propagation time difference between a transmitter and a receiver for transmitting or receiving ultrasonic waves in a fluid, fluctuation detecting means for detecting a fluctuation waveform of the fluid, and the flow rate detecting means Pulsation measurement means for starting the measurement of the fluctuation component near zero of the AC component, and flow rate calculation means for processing the signal of the flow rate detection means, the flow rate from the propagation time difference at the flow rate around the average of the fluctuation waveform Since the measurement is performed, an accurate average flow rate can be obtained in a short time by ultrasonic measurement even if there is a fluctuating flow.

(3) The fluctuation detecting means is constituted by pressure detecting means for detecting the pressure in the fluid. Since the fluctuation in the flow rate is detected by the fluctuation in the pressure, the fluctuation waveform can be easily detected. It can be shared with pressure detection means provided for monitoring and purpose.

(4) The fluctuation detecting means is activated based on the measured value of the flow rate detecting means, and the fluctuation detecting means is operated only when there is a fluctuation, so that power consumption can be reduced.

(5) When the AC component value of the fluctuation detecting means is equal to or more than a predetermined value, the pulsation detecting means measures the pulsation. Therefore, the pulsation detecting means measures only when the fluctuation is large. Measurement can be performed.

(6) An increase / decrease detecting means for judging the direction in which the flow rate increases / decreases is provided. The flow rate value starts to measure near zero when the flow rate increases, and the flow value starts to measure near zero when the flow rate decreases. Since the flow rate is calculated from the average, the average flow rate with little error can be measured even if the measurement time is long.

(7) Increasing / decreasing detecting means for judging the direction in which the flow rate increases / decreases, and switching means for changing the transmission direction of the transmitter / receiver, measuring near zero when the flow rate increases, and measuring the flow rate after operating the switching means Since the measurement is performed near zero at the time of the decrease and the flow rate is calculated from the propagation time difference, the average flow rate with few errors can be measured even if the measurement of the propagation time by the ultrasonic wave becomes long.

(8) Flow rate detection means for detecting the flow rate of the fluid, fluctuation detection means for detecting the fluctuation waveform of the fluid, cycle detection means for obtaining the fluctuation cycle from the fluctuation means, and zero of the AC component of the fluctuation waveform A pulsation measuring means for starting the measurement of the flow rate detecting means a predetermined time before and ending the measurement after the predetermined time from zero, and a flow rate calculating means for processing a signal of the flow rate detecting means; Since the flow rate before and after the center is measured, the average flow rate can be obtained by one measurement, and the accurate average flow rate can be measured in a short time.

[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 at the time of periodic flow fluctuation in the apparatus.

FIG. 3 is a block diagram of a flow rate measuring device according to a second embodiment of the present invention.

FIG. 4 is a flow rate waveform chart at the time of a periodic flow rate change in the apparatus.

FIG. 5 is a block diagram of a flow measurement device according to a third embodiment of the present invention.

FIG. 6 is a flow rate waveform chart at the time of periodic flow rate fluctuation in the apparatus.

FIG. 7 is a block diagram of a conventional flow measurement device.

FIG. 8 is a flow waveform diagram of the same device.

[Explanation of symbols]

 7 Flow rate detecting means (Transceiver) 8 Flow rate calculating means 14 Switching means 16 Fluctuation detecting means (Pressure detecting means) 17 Pulsation measuring means 20 Increase / decrease detecting means 21 Period detecting means

Claims (8)

[Claims] 1. A flow rate detecting means for detecting a flow rate of a fluid, a fluctuation detecting means for detecting a fluctuation waveform of a fluid, and a pulsation measuring means for starting the measurement of the flow rate detecting means near zero of an AC component of the fluctuation waveform. And a flow rate calculating means for processing a signal of the flow rate detecting means. 2. A flow rate detecting means for calculating a flow rate based on an ultrasonic propagation time difference between a transmitter and a receiver for transmitting and receiving an ultrasonic wave in a fluid, a fluctuation detecting means for detecting a fluctuation waveform of the fluid, and a measurement of the flow rate detecting means. A flow rate measuring apparatus comprising: a pulsation measuring means which starts near zero of an AC component of the fluctuation waveform; and a flow rate calculating means for processing a signal of the flow rate detecting means. 3. The flow rate measuring device according to claim 1, wherein the fluctuation detecting means comprises pressure detecting means for detecting a pressure in the fluid. 4. The flow rate measuring device according to claim 1, wherein the fluctuation detecting means is activated based on a measured value of the flow rate detecting means. 5. The flow rate measuring device according to claim 1, wherein when the AC component value of the fluctuation detecting means is equal to or more than a predetermined value, the flow rate is measured by the pulsation detecting means. 6. An increase / decrease detecting means for judging a direction in which the flow rate increases / decreases, wherein the flow rate value starts measurement near zero when the flow rate increases and the flow value starts measurement near zero when the flow rate decreases. The flow rate measuring device according to claim 1, wherein the flow rate is calculated from the average. 7. An increase / decrease detecting means for judging a direction in which a flow rate increases / decreases, and a switching means for changing a transmission direction of a transceiver,
3. The flow rate measuring device according to claim 2, wherein measurement is performed near zero when the flow rate increases, and measurement is performed near zero when the flow rate decreases after operating the switching unit, and the flow rate is calculated from the propagation time difference. 8. A flow rate detecting means for detecting a flow rate of a fluid, a fluctuation detecting means for detecting a fluctuation waveform of the fluid, a cycle detecting means for obtaining a fluctuation cycle from the fluctuation detecting means, and a zero of an AC component of the fluctuation waveform. A flow measuring device comprising: a pulsation measuring means for starting the measurement of the flow rate detecting means a predetermined time before and ending the measurement after the predetermined time from zero, and a flow calculating means for processing a signal of the flow detecting means.