JP2003156373A - Flow rate change detector for ultrasonic flowmeter, and ultrasonic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ultrasonic flowmeter, which is simple and low cost have a small current consumption and which can accurately detect the flow rate change frequency and a flow rate, and to provide a flow rate change detector for the ultrasonic flowmeter used therefor. SOLUTION: The flow rate change detector for the ultrasonic flowmeter comprises a transmitting circuit 5 for repeating the transmission and the reception of the ultrasonic waves in a faster period than that of the changing flow rate occurring in the flow by transmitting and receiving the wave between at least two vibrators 1 and 2 provided at the upstream side and the downstream side to the flow, a receiving wave detector 7, a time-measuring circuit 9 and a microcomputer 10 for detecting the fluctuation period of the flow rate, based on the propagation times of the transmitted and received ultrasonic waves.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate fluctuation detecting device for an ultrasonic flow meter capable of detecting fluctuations in flow rate with a simple structure, and accurately detects flow rate when there is fluctuation in flow rate in a predetermined cycle. The present invention relates to an ultrasonic flow meter capable of performing the above, and an ultrasonic flow meter capable of detecting a flow rate fluctuation period (frequency) to accurately detect a flow rate,
For example, the present invention relates to a battery-driven ultrasonic gas meter that measures the flow rate from the propagation time of ultrasonic waves.

[0002]

2. Description of the Related Art A pair of ultrasonic transducers are arranged to face each other at a predetermined distance along a fluid conduit, and ultrasonic pulses are alternately applied in a forward direction and a reverse direction with respect to a gas flow. The flow velocity of the gas flowing in the gas flow path is intermittently calculated based on the propagation time of the ultrasonic waves that are sent and received and propagated in the gas flow direction and the opposite direction, and this flow speed is multiplied by the cross-sectional area of the gas flow path. There is known an ultrasonic flow meter that is adapted to obtain a flow rate. In this type of ultrasonic gas meter, the supply gas pressure may fluctuate due to some cause, and this pressure fluctuation may cause a pulsating flow or pulsation in which the gas flow velocity changes with time. Gas heat pumps, water heaters, and the like are major causes of this.

An ultrasonic flowmeter for detecting such a pulsating flow and measuring the flow rate with high accuracy is disclosed in Japanese Patent Laid-Open No. 2001-4419.
The official gazette is known. This is because when measuring the flow rate of a gas or liquid that has flow rate fluctuations or pressure fluctuations, it is possible to measure the flow rate value stably and accurately by detecting and measuring the fluctuation information. And a first vibrating means and a second vibrating means for transmitting and receiving sound waves.
A flow rate detecting means for measuring a propagation time of a sound wave transmitted / received by the vibrating means to detect a flow rate; and a fluctuation detecting means for measuring a pressure fluctuation in the flow passage in at least one of the first vibrating means and the second vibrating means. A measurement control unit that starts measurement in synchronization with the timing of pressure fluctuation of the fluctuation detection unit is provided.

[0004]

In the above-mentioned prior art, 2
Two oscillators are composed of piezoelectric elements, and these oscillators are used for transmission and reception for measuring the propagation time, and at least one of these oscillators is used to detect pressure fluctuations.
For this reason, the usage of the vibrator must be properly used for both the measurement of the propagation time and the detection of the pressure fluctuation, and the switching means for that purpose must be configured. In addition, since the propagation time measurement, that is, the flow rate measurement is performed in synchronization with the pressure fluctuation and from the predetermined time, the circuit configuration becomes complicated, and the influence of the pressure fluctuation detection accuracy and responsiveness is affected. Therefore, there is a problem that there is a limit in improving the accuracy of flow rate measurement. Further, in the related art, since the fluctuation is detected regardless of the fluctuation (pulsation) cycle that occurs in the flow, useless detection calculation operation and the like are also required, which causes a problem that the current consumption increases.

The present invention has been made to solve the above-mentioned problems, and it is simple, low-cost, consumes less current, and can accurately detect the flow rate fluctuation period and flow rate. An object of the present invention is to provide a flow rate fluctuation detection device for a flowmeter and an ultrasonic flowmeter used therefor.

[0006]

In order to solve the above problems, the present invention measures the flow rate by transmitting and receiving ultrasonic waves between at least two transducers provided on the upstream side and the downstream side of a flow. In the flow rate fluctuation detecting device for an ultrasonic flow meter, a first transmission / reception repeating unit that repeats transmission / reception of the ultrasonic wave at a cycle faster than a variation flow rate generated in the flow, and the ultrasonic wave transmitted / received by the first transmission / reception repeating unit. And a fluctuation cycle detecting means for detecting the fluctuation cycle of the flow rate based on the propagation time of the flow rate. Here, the first transmission / reception repeating means, in the embodiment,
It is composed of a timing circuit 8, a transmission circuit 5, an amplifier 6, and a received wave detection circuit 7, and the fluctuation cycle detection means is composed of a time measurement circuit 9 and a microcomputer.

In the above structure, the first transmission / reception repeating unit may be characterized in that the transmission time of the ultrasonic wave is managed by a timer, and the first transmission / reception repeating unit may transmit the ultrasonic wave. The time can be managed based on the measured flow rate value or the magnitude of the fluctuation thereof, and further, the transmission of ultrasonic waves by the first transmission / reception repeating means is performed from upstream to downstream, or from downstream to upstream. It can be characterized in that it is performed in the same direction and the fluctuation period of the flow rate is obtained from the fluctuation of the propagation time. Further, it is possible to detect the fluctuation period of the flow rate by using FFT calculation or correlation function calculation for the obtained propagation time.

Further, the present invention is an ultrasonic flowmeter for transmitting and receiving ultrasonic waves between at least two transducers provided on the upstream side and the downstream side with respect to a flow that fluctuates in a predetermined fluctuation cycle and measuring the flow rate. At a frequency that is an integral multiple of a fluctuating frequency having the predetermined fluctuating period, based on a second transmission / reception repeating unit that repeats transmission / reception of the ultrasonic wave, and a propagation time of the ultrasonic wave transmitted / received by the second transmission / reception repeating unit. And a flow rate detecting means for detecting the flow rate. Here, the second transmission / reception repeating means is composed of the timing circuit 8, the transmitting circuit 5, the amplifier 6 and the received wave detecting circuit 7 in the embodiment, and the fluctuation cycle detecting means is composed of the time measuring circuit 9 and the microcomputer. ing.

In the above structure, the period for repeating the transmission / reception of ultrasonic waves by the second transmission / reception repeating means may be an integral multiple of the fluctuation period, and an integral multiple of the fluctuation frequency. Among the period of transmitting and receiving ultrasonic waves at the frequency of, it is also possible to transmit ultrasonic waves in mutually different directions in the odd number of the fluctuation cycle and the even number of the fluctuation cycle, and further, the fluctuation The flow rate fluctuation detecting device for an ultrasonic flowmeter according to any one of claims 1 to 5, wherein a cycle is obtained as the predetermined cycle.

According to the above configuration, the presence or absence of a pulsation (fluctuation in flow rate) and the pulsation frequency are detected from the fluctuation of the propagation time obtained by the high-speed measurement sampling, and the minimum measurement sampling necessary for the pulsation is carried out. This makes it possible to unify the usage of the oscillator into one method of measuring the propagation time of ultrasonic waves required for flow rate measurement, which simplifies the circuit configuration and arithmetic circuit, and also facilitates improvement of accuracy and low consumption. It is possible to achieve both electric power and improved pulsation resistance.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1. FIG. 1 is a block diagram showing the overall configuration of an ultrasonic gas meter as an ultrasonic flow meter of the present invention. As shown in FIG. 1, the ultrasonic gas meter is composed of, for example, a piezoelectric element, and has at least two units for transmitting or receiving ultrasonic waves.
Oscillators 1 and 2 and switch means 3 and 4 for switching at least two oscillators to a transmitting side or a receiving side.
And a transmission circuit 5 that forms a voltage for ultrasonic transmission and applies it to a transducer (for example, 1) on the transmission side, and a transducer (for example, 2) on the ultrasonic reception side. An amplifier 6 that amplifies the output voltage, a received wave detection circuit 7 that detects a received wave from the output of the amplifier 6, and the above-mentioned at least two vibrators 1 and 2 transmit and receive ultrasonic waves to each other to detect flow rate and pulsation. Timing circuit 8 that forms a predetermined timing pulse necessary for the operation, a time measurement circuit 9 that measures time based on the formation timing of timing circuit 8, and a flow rate calculation based on the measurement time of time measurement circuit 9. Microcomputer as a flow rate calculation means 1
It is configured with 0 and.

The flow rate measuring operation based on the above configuration is as follows:
For example, at a certain point in time, when the oscillator 1 on the upstream side is excited as a transmitter oscillator by the timing circuit 8 via the transmitter circuit 5, an ultrasonic wave is propagated through a flow path (not shown), and this is an oscillator on the downstream side. When received at 2, the output is amplified by the amplifier 6 and detected by the received wave detection circuit 7. The time measurement circuit 9 determines the propagation time for the ultrasonic wave to propagate from the upstream side to the downstream side from the difference between the time point when the ultrasonic wave is emitted and the time point when the received wave detection circuit 7 receives the ultrasonic wave. Similarly,
At some other time, the transmitting side and the receiving side of the transducers 1 and 2 are reversed, and the propagation time for the ultrasonic wave to propagate from the downstream side to the upstream side is obtained. Then, the microcomputer 10 calculates the flow velocity / flow rate based on the difference between these propagation times. Since this calculation method is publicly known, its explanation is omitted here.

FIG. 2 shows the operation of the first embodiment.
It is a figure which shows the transmission sampling timing for detecting a pulsation (flow rate fluctuation) frequency. The sampling timing shown in FIG. 2 transmits ultrasonic waves in a fixed direction from upstream to downstream, or from downstream to upstream at intervals of a frequency higher than the pulsation frequency to be detected (for example, 1000 Hz or more for a pulsation frequency of 500 Hz), The presence or absence of pulsation (fluctuation in flow rate) and its cycle are detected from the obtained variation in propagation time. As an example of the period detection method, FFT calculation is used for the obtained propagation time data. Further, the correlation function calculation for the propagation time data may be used. At the sampling timing shown in FIG. 2, the ultrasonic transmission cycle is set to 1
Since it is ms, 500 according to the sampling theorem.
It is possible to detect pulsating frequencies up to Hz or frequencies corresponding thereto.

Embodiment 2. FIG. 3 is a diagram showing ultrasonic wave transmission timing as an operation in the second embodiment of the present invention. In the first embodiment shown in FIG. 2, ultrasonic wave transmission in the same direction is repeated at a constant cycle, but in the second embodiment,
Pulsation detection is performed by repeating a similar operation with different directions as one pair. In that case, it is possible to obtain not only the change in the propagation time of the ultrasonic waves but also the change based on the flow rate value obtained from the propagation times measured in pairs. In addition, also here, FFT
Calculation or correlation function calculation can be used.

Embodiment 3. FIG. 4 is a diagram showing measurement sampling timing which is an operation in the third embodiment of the present invention. The sampling shown in FIG. 4 is a sampling method that consumes low power and reduces an error with respect to pulsation.
It is an example of sampling at a frequency that is an integral multiple of the pulsation frequency based on the information of the fundamental frequency (cycle) of the pulsation detected by the methods of the first and second embodiments. In FIG. 4, 4 times is shown. The magnitude of the pulsation harmonic component determines how many times the pulsation frequency is used. Since the transmission direction switching time within one pair may cause a measurement error, it is desirable that the time is as short as possible. In addition, in FIG.
Measurement is carried out over a period. The shorter this cycle is, the lower the power consumption becomes. However, when the cycle is long, the number of data to be measured increases, and thus the averaging effect enables accurate measurement. The degree of this cycle is determined by the magnitude of pulsation and the target accuracy.

Fourth Embodiment FIG. 5 is a diagram showing measurement sampling timing which is an operation in the fourth embodiment of the present invention. Although FIG. 5 shows a sampling method for reducing pulsation errors with low power consumption as in the third embodiment, the difference is that the ultrasonic wave transmission direction is switched for each pulsation cycle. As described in the third embodiment, the transmission direction switching time within one pair may cause a measurement error. Therefore, it is desirable that the transmission direction switching time be as short as possible. However, in order to stabilize the processing time of time measurement and the circuit, this time is required. There is a limit to the shortening of.
On the other hand, in the fourth embodiment, since the transmission direction is switched every cycle, the switching time can be extended to the sampling interval which is an integral multiple of the pulsation cycle. FIG. 5 shows an example of performing transmission from upstream to downstream in the first cycle and transmitting from downstream to upstream in the second cycle. In this system, the period required for measurement is an even period of the pulsation frequency.

Embodiment 5. FIG. 6 is a flowchart showing an operation algorithm in the fifth embodiment of the present invention. In the fifth embodiment, ultrasonic wave transmission for pulsation detection (for example, the operation of the first embodiment) is performed once (S1, Y) every fixed time (5 minutes) by timer management (S1) (S2). ), The magnitude of the fluctuation is obtained from the propagation time, and when the magnitude exceeds a certain threshold value (S3, Y), it is determined that there is pulsation, and the period is calculated (S4). On the other hand, when it is less than or equal to a certain threshold value (S3, N), it is determined that pulsation does not occur (S5).

At timings other than the above processing (S1,
N), the process is switched about every 1 second depending on the presence or absence of pulsation (S6). When it is determined that there is pulsation (S6,
In N), based on the basic frequency (basic cycle) of the pulsation, the sampling as in the third and fourth embodiments is repeated once per second (one block) (S7). On the other hand, when it is determined that there is no pulsation (S6, Y), low power consumption is emphasized and, for example, ultrasonic waves are transmitted once per second (S8). In this case, one pair will be formed in 2 seconds.

Then, in the embodiment, the confirmation of the presence or absence of pulsation is repeated again after the elapse of a certain fixed time of 5 minutes. By doing so, it is possible to reduce power consumption when there is no pulsation, and when there is pulsation, it is possible to cope with the pulsation with the minimum necessary power consumption according to the pulsation. In addition to the fixed cycle of the ultrasonic wave transmission for pulsation detection, in order to reduce the power consumption, it may be determined based on the pulsation size or the average flow rate. For example, even if pulsation occurs at a large flow rate, the influence on the error is small, so that it is possible to extend the pulsation confirmation cycle and reduce power consumption. Or
When the average flow rate changes, it means that there is a change in the gas equipment used, and it is expected that this will change the pulsation situation. However, the power consumption can be reduced by extending the pulsation detection period other than that.

According to the embodiment of the present invention, since the presence or absence of pulsation and the pulsation frequency are detected from the fluctuation of the propagation time obtained by the high-speed measurement sampling, the minimum necessary measurement sampling is performed. It is possible to achieve both low power consumption and improved pulsation performance. Further, since it is not necessary to install an extra sensor for measuring the fluctuation of the pulsation, it is possible to implement the pulsation countermeasure with a small size and low cost.

[0021]

As described above in detail, according to the present invention, an ultrasonic flowmeter and a flowmeter capable of detecting flow rate fluctuations and flow rates with high accuracy, low cost, low current consumption, and the like are provided. It is possible to provide a flow rate fluctuation detection device for an ultrasonic flow meter used.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an ultrasonic gas meter as an ultrasonic flow meter of the present invention.

FIG. 2 is a diagram showing ultrasonic wave transmission timing as an operation in the first embodiment.

FIG. 3 is a diagram showing ultrasonic wave transmission timing as an operation in the second embodiment of the present invention.

FIG. 4 is a diagram showing measurement sampling timing, which is an operation in the third embodiment of the present invention.

FIG. 5 is a diagram showing measurement sampling timing, which is an operation in the fourth embodiment of the present invention.

FIG. 6 is a flowchart showing an operation algorithm in the fifth embodiment of the present invention.

[Explanation of symbols]

1, 2 oscillators, 3, 4 switching means, 5 transmission circuits,
6 amplifier, 7 received wave detection circuit, 8 timing circuit, 9 time measuring circuit, 10 microcomputer.

Claims (10)

[Claims] 1. A flow rate fluctuation detecting device for an ultrasonic flow meter, which transmits and receives ultrasonic waves between at least two transducers provided on the upstream side and the downstream side with respect to a flow to measure the flow rate, and occurs in the flow. A first transmission / reception repeating unit that repeats transmission / reception of the ultrasonic wave at a cycle faster than the variation flow rate, and a variation cycle that detects the variation period of the flow rate based on the propagation time of the ultrasonic wave transmitted / received by the first transmission / reception repeating unit. A flow rate fluctuation detection device for an ultrasonic flow meter, comprising: a detection unit. 2. The ultrasonic flowmeter according to claim 1, wherein the first transmission / reception repeating unit manages an ultrasonic wave transmission time by a timer. Flow rate fluctuation detector. 3. The flow rate fluctuation detecting device for an ultrasonic flowmeter according to claim 1 or 2, wherein the first transmission / reception repeating means measures the ultrasonic wave transmission time or the measured flow rate value or its fluctuation magnitude. A flow rate fluctuation detection device for an ultrasonic flow meter, characterized in that it is managed based on 4. The flow rate fluctuation detection device for an ultrasonic flowmeter according to claim 1, wherein the first transmission / reception repeating means transmits ultrasonic waves from upstream to downstream, or from downstream to upstream. A flow rate fluctuation detection device for an ultrasonic flow meter, characterized in that the flow rate fluctuation period is obtained from fluctuations in propagation time in the same direction. 5. The flow rate fluctuation detecting device for an ultrasonic flowmeter according to claim 1, wherein the fluctuation period of the flow rate is detected using FFT calculation for the obtained propagation time. Flow rate detection device for ultrasonic flowmeter. 6. The flow rate fluctuation detecting device for an ultrasonic flowmeter according to claim 1, wherein the fluctuation cycle of the flow rate is detected by using a correlation function calculation for the obtained propagation time. Characteristic ultrasonic flow meter flow rate fluctuation detection device. 7. An ultrasonic flowmeter for transmitting and receiving ultrasonic waves between at least two transducers provided on an upstream side and a downstream side with respect to a flow that fluctuates at a predetermined fluctuation cycle to measure a flow rate, wherein: The frequency based on the propagation time of the ultrasonic waves transmitted and received by the second transmission and reception repeating means, and the second transmission and reception repeating means that repeats the transmission and reception of the ultrasonic waves at a frequency that is an integral multiple of the fluctuation frequency having An ultrasonic flowmeter, comprising: a flow rate detecting means for detecting. 8. The ultrasonic flowmeter according to claim 7, wherein a period in which the ultrasonic wave is repeatedly transmitted and received by the second transmission / reception repeating means is an integral multiple of the fluctuation cycle. . 9. The ultrasonic flowmeter according to claim 8, wherein an odd number of the fluctuation cycle and an even number of the fluctuation cycle are included in a period in which ultrasonic waves are transmitted and received at a frequency that is an integral multiple of the fluctuation frequency. An ultrasonic flowmeter, which transmits ultrasonic waves in different directions. 10. The ultrasonic flowmeter according to any one of claims 7 to 9, wherein the fluctuation cycle is obtained as the predetermined cycle. An ultrasonic flowmeter, comprising: