JPS6123921A - Flow velocity and flow rate measuring device - Google Patents

Abstract

PURPOSE:To extract a noisy signal from fluid by providing a demodulating circuit which extracts the noisy signal from a received wave and a correcting circuit which removes a fixed signal component due to variance in characteristics among transmitters or receivers from a demodulation output. CONSTITUTION:The measuring device is equipped with the demodulating circuit 4 which extracts the noisy signal from the received wave and the correcting circuit 5 which removes the fixed signal component due to variance in characteristics among transmitters or receivers from the demodulation output. This correcting circuit 5 equalize the number of stages of CCDs, etc., constituting a delay circuit 55 to the number N of the receivers, equalizes a clock frequency for delay quantity control to the switching frequency f1 of the receivers, and sets the magnifying power of a multiplying circuit 54 to 0.9. Consequently, the signal component due to variance in characteristics among the receivers is extracted through averaging operation and subtracted from the demodulation output to extract the noisy signal from the fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a correlation type flow rate/flow rate measuring device that measures the flow rate or flow rate of a fluid using, for example, ultrasonic waves.

<Background of the Invention> Conventionally, two types of flow velocity/flow measuring devices using ultrasonic waves have been put into practical use: a propagation time difference type and a Doppler type. The former method uses the difference in the propagation time of ultrasonic waves when emitting ultrasonic waves in the direction along the flow of fluid and in the direction against the flow to determine the flow velocity and flow rate. The latter method uses the Doppler effect that occurs between ultrasonic waves and reflected waves when emitting ultrasonic waves to contaminants such as dirt and bubbles in the fluid to determine the flow velocity and flow rate. However, in the case of the former propagation time difference method, if there are contaminants such as dirt in the fluid, the ultrasonic path is obstructed, making it difficult to measure the flow velocity and flow rate.On the other hand, in the latter Doppler one-way method, If there are no contaminants present in the fluid, reflected waves cannot be obtained, and measurement of flow velocity and flow rate becomes difficult as well. Therefore, in each of these methods, whether or not the flow velocity/flow rate can be measured and its accuracy are affected by the presence or absence of contaminants in the fluid.

Therefore, in recent years, a correlation-type flow velocity/flow rate measuring device has been proposed that can measure flow velocity/flow rate regardless of the presence or absence of contaminants.

This correlation type device focuses on the fact that ultrasonic waves propagating through the fluid to be measured are modulated by the presence of particles in the fluid, fluid vortices, vibrations, etc., and demodulates this modulated component. This method extracts the state of the fluid as a kind of noisy signal.

The example of the correlation type device shown in FIG. 3 has a transmitter IA that emits ultrasonic waves and a receiver 2A that receives the ultrasonic waves facing each other in a direction perpendicular to the flow of fluid, and a certain distance downstream. Similar transmitters IB and receivers 2B are placed at the same locations, and the noisy signals are extracted at these two points, and the fluid velocity and flow rate are measured from the correlation between both signals.

However, in the case of the illustrated example, there is a problem in that the noisy signal has poor preservation, and the state of the fluid deteriorates while the fluid moves over a distance, causing the signal pattern to change.

FIG. 4 shows an example of a device which has been improved by the inventor in order to solve this problem. In the illustrated device, a receiver 2 disposed opposite a transmitter 1 is configured by arranging a plurality of receivers 20 and 20, and each receiver 20 is sequentially switched by a switching circuit 3 to transmit and receive ultrasonic waves. After the demodulation circuit 4 extracts the noisy signal, the speed of the noisy signal is determined by the variable delay circuit 61, the waveform discrimination circuit 62, and the arithmetic circuit 63, and the flow velocity and flow rate of the fluid are calculated. It is something to do. According to the device with this kind of configuration, the noisy signal is highly preserved and it is possible to measure the flow velocity and flow rate with high precision in a short time. Because of this structure, the received wave contains fixed signal components due to variations in the characteristics of each receiver, resulting in problems such as the inability to obtain a sufficiently large signal strength for noisy signals.

<Purpose of the Invention> The present invention is capable of measuring flow velocity and flow rate regardless of the presence or absence of contaminants in a liquid, such as the propagation time difference method or the Doppler one-way method, and improves the drawbacks of conventional correlation-type methods. The purpose of this study is to provide a new flow velocity/flow rate measuring device.

<Configuration and Effects of the Invention> In order to achieve the above object, the present invention configures a receiver by arranging a plurality of receivers, for example, and sequentially switches each receiver with a switching circuit to receive ultrasonic waves. After that, the demodulated output of the received wave is corrected by a correction circuit to remove fixed signal components caused by variations in characteristics of each receiver from the demodulated output.

According to the present invention, even if there are variations in characteristics among the receivers arranged in a row, fixed signal components caused by the variations are removed, and noisy signals indicating fluid conditions are minimized. However, this can be extracted reliably, and there is no problem in measuring the flow rate or flow rate.

Furthermore, since the device of the present invention performs correlation using noisy signals obtained by high-speed switching, the noisy signals to be correlated are highly conserved, and flow velocity and flow rate can be measured with high precision in a short time. Unlike the conventional propagation time difference method or the Doppler one-way method, the measurement accuracy and accuracy are not influenced by the presence or absence of contaminants in the fluid, and the present invention has a remarkable effect of achieving the purpose of the invention.

<Description of Examples> FIG. 1 shows a flow velocity/flow rate measuring device according to the present invention. The illustrated device uses ultrasonic waves to measure the flow velocity and flow rate of fluid flowing inside a tube 7, and a pair of ultrasonic transmitters 1 and Receivers 2 are placed opposite each other. The transmitter 1 converts the high frequency signal outputted by the ultrasonic oscillator 1° into an ultrasonic wave, and projects the ultrasonic wave into the fluid within the tube 7. This ultrasonic wave is propagated while being subjected to amplitude modulation or phase modulation due to the presence of fine particles in the fluid, fluid vortices, vibrations, etc., and reaches the receiver 2 where it is received.

The receiver 2 of the present invention is constructed by arranging a plurality of receivers 20, 20 in line along 4 in the flow direction, - each receiver 20 is sequentially switched in the flow direction using a switching circuit 3; Receive modulated ultrasound waves. This switching operation is called scanning, and the switching speed is set to a sufficiently high value compared to the flow velocity. Here, if the length of the receiver 2 is N, the number of receivers 20 constituting the receiver 2 is N, and the frequency of the switching signal of the switching circuit 3 output by the oscillator 30 is 1, then the switching speed Vs is as follows. It is given by the formula 0.

The switching circuit 3 transfers the received wave obtained from the receiver 2 to the amplifier circuit 3.
1 and output to the demodulation circuit 4. This demodulation circuit 4 demodulates the modulation component, and a noisy signal is output every scanning period in the switching circuit 3. Note that the scanning period refers to the time required to switch all receivers 20. The demodulated output of the demodulation circuit 4 is a signal component resulting from variations in the characteristics of the receiver 20 superimposed on the noisy signal to be detected, and is output from the delay circuit 51 constituting the correction circuit 5. It is divided and sent to the subtraction circuit 52. The delay circuit 51 has BBD (Bucket
Brigade Device), CCD (Ch
The subtracting circuit 52 subtracts the demodulated output of the demodulating circuit 4 and the delayed output of the delay circuit 51 to extract a difference signal.

Now, if the number of receivers 20 is N and the switching frequency of the switching circuit 3 is fl, then the scanning period is -. -The number of stages of CCD etc. of the 10,000 delay circuit 51 is the same as the number of receivers -N,
If the clock frequency for delay control is set to fl, which is the same as the switching frequency, then the following equation is obtained. Therefore, the delayed output in this case is
It becomes the same as the demodulated output one scanning period ago. Here, the signal component caused by variations in the characteristics of each receiver 20 is fixed and always the same, while the noise signal changes every scanning period, so the subtraction circuit 52 changes the signal component due to the characteristics. The subtraction circuit 52 outputs a difference value (hereinafter referred to as "difference signal") between the noisy signals in the previous and subsequent scanning cycles.

This difference signal is sent to the variable delay circuit 61 and the waveform discrimination circuit 62 of the signal processing circuit 6, respectively.
checks the phase difference between this differential signal and the delayed output of the variable delay circuit 61.

The variable delay circuit 61 is formed of BBD, CCD, etc., the number of stages is N, which is the same as the number of receivers, and the delay amount m is
+If the clock frequency used is 12, the delay amount T is expressed by the following equation.

The waveform discrimination circuit 62 observes the difference signal at each scanning period, and compares the difference signal from the previous scan (output of the variable delay circuit 61) with the difference signal from the current scan (output from the subtraction circuit 52). , determine whether the two waveforms match.

Now, assuming that the output waveform of the subtraction circuit 52 is S (t), if the waveform discrimination circuit 62 recognizes that the waveforms match, the following equation 0 holds true between the signal waveforms to be compared.

In the above formula, ■ is the flow velocity of the fluid, and this flow velocity V is given by the following formula 0 from the formula ■■. However, Δf-f2-[1.

Thus, when there is a phase difference between the two signal input waveforms, the waveform discrimination circuit 62 changes the clock frequency "2" that controls the delay amount of the variable delay circuit 7 to make both waveforms match. 62 or when a match is determined,
In the arithmetic circuit 63, the switching frequency f1 and the clock frequency 12 are input as data, and the flow rate is calculated by the above formula 0.
, and further calculate the flow rate by multiplying the flow velocity ■ by the cross-sectional area of the fluid.

FIG. 2 shows another embodiment of the correction circuit 5. In FIG.

The correction circuit 5 includes an adder circuit 53, a multiplier circuit 54, a delay circuit 55, and a subtracter circuit 56. For example, the delay circuit 5
The number of stages of CCD etc. configuring 5 is made to match the number of receivers N,
Further, the clock frequency for controlling the amount of delay is set to be the same as the switching frequency E1 of the receiver 20, and the multiplier of the multiplier circuit 54 is set to 0.
．． Set to 9. In the case of this embodiment, the function is to average the waveforms of 10 scanning cycles and extract the difference from the waveform obtained in the next scanning. Therefore, this correction circuit 5 extracts signal components caused by variations in characteristics of the receiver through the averaging operation, and subtracts these signal components from the demodulated output to extract noise signals in the fluid. Can be done.

Although each of the above-mentioned embodiments is a flow rate/flow measuring device using ultrasonic waves, the present invention is not limited to ultrasonic waves, but can also be applied to devices using electromagnetic waves.

[Brief explanation of the drawing]

Fig. 1 is a block diagram illustrating the principle and circuit configuration of the flow rate/flow measuring device according to the present invention, Fig. 2 is a block diagram illustrating another embodiment of the correction circuit, and Fig. 3 shows the configuration of a conventional example. The explanatory diagram, FIG. 4, is a block explanatory diagram showing the principle and circuit configuration of a correlation type device that is an improvement over the conventional example. 1... Transmitter 2... Receiver 20
...Receiver 3...Switching circuit 4...
・Demodulation circuit 5... Correction circuit Patent applicant Tateishi Electric Co., Ltd. +114- Figure fl A3 Figure -127, -

Claims (1)

[Claims] A detection wave such as an ultrasonic wave is emitted into the fluid to be measured, a noisy signal is detected from the fluid, and the flow velocity and flow rate of the fluid are measured based on the moving speed of the noisy signal. The device includes a transmitting means and a receiving means arranged opposite to each other in a direction perpendicular to the flow of the fluid to be measured, at least one of which is configured by arranging a plurality of transmitting or receiving elements, and a detection wave by sequentially switching the transmitting or receiving elements. a switching circuit for transmitting and receiving waves, a demodulation circuit for extracting the noisy signal from the received wave, and a correction circuit for removing fixed signal components caused by variations in characteristics of the transmitter or receiver from the demodulated output. A flow rate/flow rate measurement device consisting of: