JPH0643909B2 - Flow velocity / flow rate measuring device and fluid carrying pipe equipped with the device - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a correlation type flow velocity / flow rate measuring device for measuring the flow velocity or flow rate of a fluid by utilizing, for example, ultrasonic waves, and a fluid transfer pipe equipped with the device. Regarding

<Background of the Invention> Conventionally, two types of flow velocity / flow rate measuring devices using ultrasonic waves have been put into practical use: a transmission time difference method and a Doppler method. The former method is a method of obtaining a flow velocity and a flow rate by utilizing a difference in propagation time of ultrasonic waves when ultrasonic waves are emitted in a direction along a flow of a fluid and a direction opposite to the flow, The latter method is a method for obtaining the flow velocity and the flow rate by utilizing the fact that the Doppler effect is generated between the ultrasonic wave and the reflected wave when ultrasonic waves are emitted to the contaminants such as dust and bubbles in the fluid. However, in the former transmission time difference method, if contaminants such as dust are present in the fluid, the ultrasonic path is obstructed, making it difficult to measure the flow velocity and flow rate, while in the latter Doppler method, If no contaminants are mixed in, reflected waves cannot be obtained, and similarly, flow velocity / flow rate measurement becomes difficult.
Therefore, in each of these methods, whether or not the flow velocity and flow rate can be measured and their accuracy depend on the presence or absence of contaminants in the fluid.

Therefore, in recent years, a correlation type flow velocity / flow rate measuring device capable of measuring the flow velocity / flow rate regardless of the presence or absence of a contaminant has been proposed.
This correlation type device focuses on the fact that the ultrasonic waves propagating in the fluid to be measured are modulated by the presence of fine particles in the fluid, the vortex of the fluid, and the vibration. Then, the state of the fluid is extracted as a kind of noisy signal.

In the correlation type device example shown in FIG. 3, a transmitter 1A that emits an ultrasonic wave and a receiver 2A that receives the ultrasonic wave are arranged so as to face each other in a direction orthogonal to the fluid flow, and further at a constant distance L downstream position. The same transmitter 1B and receiver 2B are provided, and the noise signals are extracted at these two points, and the flow velocity and flow rate of the fluid are measured from the correlation between the two signals. However, in the case of the method of the illustrated example, there is a problem that the storage property of the noisy signal is poor, the state of the fluid collapses while the fluid moves the distance L, and the signal pattern changes.

FIG. 4 shows an example of a device which has been improved by the inventor to solve this problem. In the illustrated apparatus, a transmitter 2 arranged opposite to the transmitter 1 is configured by arranging a plurality of receivers 20, 20 in line, and each receiver 20 is switched by a switching circuit 3.
The ultrasonic wave is transmitted / received by sequentially switching by, and after the noise signal is extracted by the demodulation circuit 4, the variable delay circuit 61,
The waveform discriminating circuit 62 and the arithmetic circuit 63 calculate the velocity of the noisy signal to calculate the flow velocity and flow rate of the fluid. According to the device of this kind of configuration, it is possible to measure the flow velocity and the flow rate in a short time and with high accuracy because the noise signal is highly conserved, but the receiver 2 has a plurality of receivers 20. Since it is configured as described above, the fixed wave component due to the variation in the characteristics of each receiver 20 is included in the received wave, which causes a problem that a sufficiently large signal strength cannot be obtained for the noisy signal. It was

<Purpose of the Invention> The present invention is capable of measuring the flow velocity and flow rate regardless of the presence or absence of contaminants in the liquid, such as the transfer time difference method and the Doppler method, and improves the drawbacks of the conventional correlation type. An object of the present invention is to provide a flow velocity / flow rate measuring device and a fluid carrying pipe equipped with the device.

<Structure and Effect of the Invention> The present invention relates to a flow velocity / flow rate measuring device and a fluid transport system for transporting a fluid in a pipe provided with the device. Transmitting means for projecting a detection wave such as an ultrasonic wave in a direction orthogonal to the fluid flow,
The receiving means is provided opposite to the transmitting means and receives the detection wave propagating while being modulated in the fluid.
At least one of the transmitting means and the receiving means is configured by arranging a plurality of transmitting or receiving elements in line, and
A switching circuit is connected to the aggregate of the transmitters or receivers to sequentially switch the transmitters or receivers at a speed higher than the flow velocity of the fluid to transmit and receive the detection wave. Further, the receiving means extracts a noisy signal obtained by demodulating a modulation component from the received signal for each switching cycle by the switching circuit, and determines the flow velocity of the fluid from the correlation between the signals before and after the extraction.
An arithmetic processing circuit for calculating the flow rate is connected. The arithmetic processing circuit includes a correction circuit that removes a fixed signal component resulting from the characteristic variation of the transmitter or the receiver from the demodulated output.

According to the present invention, even if there are variations in characteristics among the aligned receivers and the like, the fixed signal component resulting from the variations is removed, so that even if the noise signal indicating the fluid state is minute, However, this can be reliably extracted, and there is no problem in measuring the flow velocity and flow rate.

Further, since the apparatus of the present invention performs correlation using a noisy signal obtained by high-speed switching, it has a high preservation property of the noisy signal to be correlated and can measure the flow velocity and the flow rate in a short time and with high accuracy. At the same time, unlike the conventional transfer time difference method and Doppler method, the presence or absence of contaminants in the fluid does not affect the possibility of measurement or the accuracy thereof, and other significant effects of achieving the object of the invention are achieved.

<Description of Embodiments> FIG. 1 shows a flow velocity / flow rate measuring device according to the present invention and a fluid transfer system including the device. Flow velocity in the example shown
The flow rate measuring device uses ultrasonic waves to measure the flow velocity and flow rate of the fluid flowing in the pipe 7, and a pair of ultrasonic transmitters 1 and a receiver are provided on the outer surface of the pipe 7 in a direction orthogonal to the flow. Body 2 is deployed oppositely. The transmitter 1 is an ultrasonic oscillator 1
The high frequency signal output by 0 is converted into an ultrasonic wave and this is converted into a tube 7
Project into the fluid inside. This ultrasonic wave is propagated while undergoing amplitude modulation or phase modulation due to the presence of fine particles in the fluid, the vortex of the fluid, vibration, etc., and reaches the receiving body 2 to be received. The receiver 2 has a plurality of receivers 20,
It is configured by arranging 20 along the direction of flow,
Each receiver 20 is sequentially switched in the flow direction by using the switching circuit 3 to receive the modulated ultrasonic waves. This switching operation is called scanning, and the switching speed is set to a value sufficiently higher than the flow velocity. Here, the length of the receiver 2 is L, the number of receivers 20 constituting the receiver 2 is N, and the oscillator 3
When the frequency of the switching signal of the switching circuit 3 output by 0 is ₁ , the switching speed V _s is given by the following equation.

The switching circuit 3 outputs the received wave obtained by the receiver 2 to the demodulation circuit 4 via the amplification circuit 31 in the arithmetic processing circuit 8. The demodulation circuit 4 demodulates the modulation component, and a noise signal is output every scanning cycle in the switching circuit 3. The scanning cycle refers to the time required to switch all the receivers 20. The demodulation output of the demodulation circuit 4 is a noise signal to be detected, on which a signal component due to variations in the characteristics of the receiver 20 is superimposed. Subtraction circuit 52
And is divided into two and sent. The delay circuit 51 has a BBD (Bu
cket Brigade Device), CCD (Charge Coupled Devi
ce) and the like, and the subtraction circuit 52 subtracts the demodulation output of the demodulation circuit 4 and the delay output of the delay circuit 51 to extract the difference signal.

Now, assuming that the number of the receivers 20 is N and the switching frequency of the switching circuit 3 is f ₁ , the scanning period is Becomes On the other hand, if the number of CCDs and the like in the delay circuit 51 is N, which is the same as the number of receivers, and the clock frequency for delay control is f _1, which is the same as the switching frequency, the delay amount of the delay output is the same as the scanning period. Becomes Therefore, the delay output in this case is the same as the demodulation output one scanning before. Here, the signal component resulting from the characteristic variation of each receiver 20 is fixed and always the same, while the noisy signal changes every scanning cycle, and therefore the characteristic of the subtractor circuit 52 is changed. The signal component caused by the variation of is subtracted, and the subtraction circuit 52 outputs a difference value of the noisy signal (hereinafter, referred to as “difference signal”) in the front-back scanning period.

This difference signal is sent to the variable delay circuit 61 and the waveform discrimination circuit 62 of the signal processing circuit 6, respectively, and the waveform discrimination circuit 62 is supplied.
Checks the phase difference between this difference signal and the delay output of the variable delay circuit 61. The variable delay circuit 61 is formed with BBDs, CCDs, etc., and if the number of stages is N, which is the same as the number of receivers, and the clock frequency for delay amount control is f ₂ , the delay amount τ is expressed by the following equation. It

The waveform discrimination circuit 62 observes the differential signal for each scanning cycle, and compares the differential signal applied to the previous scanning (output of the variable delay circuit 61) and the differential signal applied to this scanning (output of the subtraction circuit 52). , It is determined whether the two waveforms match.

Now, assuming that the output waveform of the subtraction circuit 52 is S (t), the following equation holds between the signal waveforms to be collated when the waveform discrimination circuit 62 finds that the waveforms match.

In the above equation, V is the flow velocity of the fluid, and this flow velocity V is given by the following equation. However Δf = f ₂ - _1.

Thus, when there is a phase difference between the two signal input waveforms, the waveform discriminating circuit 62 changes the clock frequency f ₂ that controls the delay amount of the variable delay circuit 7 to match the two waveforms.
When the waveform discrimination circuit 62 makes a coincidence discrimination,
In the arithmetic circuit 63, the switching frequency f ₁ and the clock frequency f ₂ are input as data, the flow velocity V is obtained by the above equation, and the flow velocity V is multiplied by the cross-sectional area of the fluid to calculate the flow rate.

FIG. 2 shows another embodiment of the correction circuit 5. The correction circuit 5 includes an adder circuit 53, a multiplication circuit 54, and a delay circuit 5.
5 and a subtraction circuit 56, for example, the number of stages of CCDs or the like that constitutes the delay circuit 55 is made equal to the number N of receivers, and the clock frequency for delay amount control is the switching frequency f _{1 of the} receiver 20.
Similarly, the magnification of the multiplication circuit 54 is set to 0.9. In the case of this embodiment, the function of averaging the waveforms for 10 skiring cycles and extracting the difference from the waveform obtained by the next scanning is performed. Therefore, according to the correction circuit 5, the signal component due to the variation in the characteristics of the receiver is extracted by performing the averaging operation, and by subtracting this signal component from the demodulation output, the noise in the fluid is reduced. The sex signal can be retrieved.

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

[Brief description of drawings]

FIG. 1 is a block diagram showing the principle and circuit configuration of a flow velocity / flow rate measuring device according to the present invention, FIG. 2 is a block diagram showing another embodiment of a correction circuit, and FIG. 3 is a configuration of a conventional example. FIG. 4 and FIG. 4 are block diagrams showing the principle and circuit configuration of a correlation type apparatus improved from the conventional example. 1 ... Transmitter, 2 ... Receiver 20 ... Receiver, 3 ... Switching circuit 4 ... Demodulator circuit, 5 ... Correction circuit

Claims (2)

[Claims] 1. A flow velocity / flow rate measuring device for measuring a flow velocity / flow rate of a fluid, the transmitting means projecting a detection wave such as an ultrasonic wave into the fluid in a direction orthogonal to the flow of the fluid, and the transmitting means. A receiving means arranged to face each other and receiving a detection wave propagating while being modulated in a fluid, wherein at least one of the transmitting means and the receiving means is configured by arranging a plurality of transmitting or receiving elements in alignment. Along with
A switching circuit for transmitting and receiving a detection wave by sequentially switching each transmission or receiver at a speed higher than the flow velocity of the fluid is connected to the aggregate of transmitters or receivers, and the receiving means receives a modulation component from the received signal. A noise processing signal obtained by demodulation is extracted for each switching cycle by the switching circuit, and an arithmetic processing circuit is connected to calculate the flow velocity / flow rate of the fluid from the correlation between the signals before and after the extraction, The flow rate / flow rate measuring device, wherein the arithmetic processing circuit includes a correction circuit that removes a fixed signal component due to variations in characteristics of the transmitter or the receiver from the demodulated output. 2. A fluid carrying pipe provided with a flow velocity / flow rate measuring device for measuring a flow velocity / flow rate of a fluid, wherein the flow velocity / flow rate measuring device is an ultrasonic wave or the like in a direction orthogonal to the flow of the fluid into the pipe. Of the detection means, and a receiving means that is provided facing the transmission means and receives the detection wave that propagates while being modulated in the fluid, and at least one of the transmission means and the reception means , With multiple transmitters or receivers aligned and configured,
A switching circuit for transmitting and receiving a detection wave by sequentially switching each transmission or receiver at a speed higher than the flow velocity of the fluid is connected to the aggregate of transmitters or receivers, and the receiving means receives a modulation component from the received signal. A noise processing signal obtained by demodulation is extracted for each switching cycle by the switching circuit, and an arithmetic processing circuit is connected to calculate the flow velocity / flow rate of the fluid from the correlation between the signals before and after the extraction, The arithmetic processing circuit is a fluid transfer pipe including a flow velocity / flow rate measuring device including a correction circuit that removes a fixed signal component caused by variations in characteristics of the transmitter or the receiver from the demodulated output.