JPH0421822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic current meter, and more particularly to an ultrasonic current meter that measures flow velocity in an ultrasonic beam direction and in a direction different from the beam direction.

In the conventional ultrasonic flow velocity type, a method was used in which the flow velocity was calculated using the Doppler shift frequency of the reflected wave from a moving object. The method using Doppler shift has a problem in that although it is possible to know the velocity component in the direction of the ultrasound beam, it is not possible to detect the velocity in a direction different from that.

In view of the above-mentioned problems of the conventional current meter, an object of the present invention is to use a structure that uses amplitude cross-correlation of ultrasonic reflected waves having at least two beam directivities, and to calculate the velocity in the beam direction and in a different direction. The purpose is to make the components detectable.

In the present invention, an ultrasonic transducer group including a plurality of transducers, an ultrasonic drive circuit for driving the plurality of transducers, and at least two of the plurality of transducers are provided.
A receiving circuit which determines beam directivity from two outputs and whose directivity is variable, wherein the receiving circuit is provided with a first receiving circuit and a second receiving circuit, and the first and second receiving circuits are one for extracting reflections having two different beam directivities from the transducers of the same ultrasonic transducer group; and a plurality of amplitude value sampling circuits receiving outputs from the first and second receiving circuits; A cross-correlation peak time difference detection circuit that calculates the time difference at which the cross-correlation peaks of each amplitude data string that is the output of each of the amplitude value sample circuits, and a speed calculation circuit that receives the output of the cross-correlation peak time difference detection circuit. Accordingly, an ultrasonic pulse current meter is provided, which is characterized by determining the velocity in the beam direction and in a direction different from the beam direction.

An ultrasonic pulse current meter as an embodiment of the present invention is shown in FIG. In FIG. 1, an ultrasonic drive circuit 12 drives a transducer 13 via a switch 14 in response to a start signal sent from a control circuit 11, and transmits ultrasonic pulses or burst waves to the outside. A reflected wave of the externally transmitted ultrasonic wave from an object is received by a transducer 13, and is supplied to an amplifier 15 via a switch 14 and amplified. The output amplified by the amplifier 15 is sent to a set of a plurality of delay circuits 16 and one
7, and based on the same principle as the phase array antenna, by setting the delay time of each delay circuit constituting each delay circuit set to a predetermined time, It can be made to have directionality. Therefore, the sets of delay circuits 16 and 17 take out reflected waves having different directivity, and add them to adder 18 or 19 for each set. The output of the adder 18 is applied to a reception amplifier circuit 20, amplified, and supplied to a first amplitude value sample and hold circuit 22 as an amplitude value sample circuit. In the first amplitude value sample and hold circuit 22, amplitude data of sample points at the same time, that is, at the same distance, are transferred to the control circuit 1.
The sample is held according to the sample position instruction from 1. The reflected wave output having another directivity from the same transducer group 13 that is applied to the adder 19 is applied to the reception amplifier circuit 21, where it is amplified and supplied to the second amplified value sample and hold circuit 23. be done. The second amplitude value sample and hold circuit 23 samples and holds amplitude data of sample points at the same time, that is, at the same distance, in response to a sample position instruction from the control circuit 11. The two data strings generated by the two amplitude value sample holes described above are applied to the cross-correlation peak time difference detection circuit 24, and the time difference at which the cross-correlation of the two data strings reaches the peak is determined.
The output of the cross-correlation peak time difference detection circuit 24 is applied to a speed calculation circuit 25, which calculates the flow speed by dividing it by the two sample point intervals and the pulse transmission interval. Note that the sample point interval is determined by the angles of the two pointing directions and the distance from the transducer to each sample point.

FIG. 2 illustrates the relationship between ultrasound transducer 41 and sample volumes 42 and 43.

Note that the sample volumes 42 and 43 may have a part in common. Transducer 41
Thus, the ultrasonic waves are emitted near the centers of the two sample volumes, and the reflected waves 44 are reflected from each sample volume and returned to the transducer. As a result, a plurality of reflected waves having different directivities are received by the transducer.

FIG. 3 shows waveforms of various parts of the ultrasonic pulse current meter shown in FIG. 1. That is, in FIG. 3, a shows the transmitted wave, b shows the received wave 1, c shows the received wave 2, d shows the sample pulse, and e shows the first amplitude value sample and hold circuit 2.
2, f is the waveform of the output of the second amplitude value sample and hold circuit 23.

FIG. 4 shows the cross-correlation peak time difference detection circuit 2.
A detailed block circuit diagram of 4 is shown. The output from the first amplitude value sample and hold circuit 22 is connected to an audio delay line 51, and the output from the second amplitude value sample and hold circuit 23 is connected to an audio variable delay line 52. The output of audio delay line 51 is connected to one input terminal of multipliers 54 and 55, and the output of audio variable delay line 52 is connected to the other input terminal of audio delay line 53 and multiplier 54. The output of audio delay line 53 is connected to the other input terminal of multiplier 55. The output of the multiplier 54 goes to the inverting input of the differential amplifier 56;
The output of multiplier 55 is connected to the non-inverting input of differential amplifier 56. The output of the differential amplifier 56 is supplied to a low-pass filter 57, and the output of the low-pass filter 57 is supplied to the next stage as the output of a cross-correlation peak time difference detection circuit, as well as a voltage controlled oscillator (VCO) 58.
connected to. The output of voltage controlled oscillator 58 is connected to a control input terminal of audio variable delay line 52.

The operation of the cross-correlation peak time difference detection circuit shown in FIG. 4 will be explained. The delay time of the fixed audio delay line 51 is τ1, and the delay time of the audio variable delay line 52 is τ52.
3. If the delay time of the fixed audio delay line 53 is τ2, and the characteristics of the voltage controlled oscillators 58 of these three delay lines are as shown in FIG. 5, then the circuit of FIG. The maximum point of cross-correlation between two input signals is tracked. Therefore, the output of the circuit in Fig. 4 has (τ3
A voltage corresponding to +1/2τ2)-τ1=τd is obtained. The above relationship is explained in FIG. 6, where the horizontal axis is time and the vertical axis is the cross-correlation value. That is,
Audio delay line 5 with a delay time of τ2
The cross-correlation of the signal that has passed through 3 and the signal that has not passed is obtained by passing through a multiplier and a low-pass filter, respectively, and the delay time of the audio variable delay line 52 is adjusted via the voltage controlled oscillator 58 so that both of them are equal. By controlling, the cross-correlation peak time difference between two inputs can be determined as τd. Note that the low-pass filter 57 is a differential amplifier 56.
Although it is connected to the output side of the differential amplifier 56, the effect is the same even if it is inserted between the differential amplifier 56 and the multiplier.

In this example, by determining the time difference between two amplitude data strings that is the peak of the cross-correlation between the amplitude data strings of two measurement points, it is possible to determine the movement of an object from one measurement point to the other measurement point. The time required for this is calculated, and the velocity of the object, that is, the flow velocity, is detected from the length of the two measurement points and the above-mentioned time difference.

In this embodiment, a delay circuit is used electrically to obtain the directivity of the ultrasonic reflected waves, but the method is not limited to this, and may be performed acoustically.

According to the present invention, velocity components in a beam direction and a direction different from the beam direction can be detected. That is, with a single probe made up of a plurality of transducers, beams having two directivities are determined by the receiving circuit, and the two beams can be used to detect speed.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of an ultrasonic pulse current meter as an embodiment of the present invention, FIG. 2 is a diagram explaining the relationship between the transducer and sample volume in the current meter of FIG. 1, and FIG. Figure 1 is a waveform diagram showing the waveforms of each part of the current meter.
A block circuit diagram showing details of the cross-correlation peak time difference detection circuit 24 in the current meter shown in FIG.
This figure and FIG. 6 are characteristic diagrams explaining the differential of the circuit of FIG. 4. 11...Control circuit, 12...Ultrasonic drive circuit, 13...Transducer, 14...
...Switch, 15...Amplifier, 16,17...Delay circuit, 18,19...Adder, 20,21...
Reception amplifier circuit, 22...first amplitude value sample and hold circuit, 23...second amplitude value sample and hold circuit, 24...cross correlation peak time difference detection circuit,
25...Speed calculation circuit.

Claims (1)

[Claims] 1. An ultrasonic transducer group consisting of a plurality of transducers; an ultrasonic drive circuit for driving the plurality of transducers; and a beam from at least two outputs of the plurality of transducers. A receiving circuit that determines directivity and is variable in the directivity, wherein the receiving circuit includes a first
a receiving circuit, a second receiving circuit;
The second receiving circuit extracts reflections having two different beam directivities from the transducers of the same ultrasonic transducer group, and a plurality of receiving circuits receive outputs from the first and second receiving circuits. an amplitude value sampling circuit; a cross-correlation peak time difference detection circuit that calculates the time difference at which the cross-correlation peaks of each amplitude data string output from each of the amplitude value sampling circuits; and an output of the cross-correlation peak time difference detection circuit; What is claimed is: 1. An ultrasonic pulse current meter characterized by comprising a velocity calculation circuit, thereby determining velocity in a beam direction and in a direction different from the beam direction.