JPS5832336B2 - ultrasonic current meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention monitors on the receiving side situations where the = part of the ultrasound does not reach the receiving section or is greatly attenuated due to bubbles or drifting occurring in the propagation path in the fluid. The present invention also relates to an ultrasonic current meter that performs measurement under conditions of normal attenuation.

An ultrasonic current meter measures the flow velocity by utilizing the fact that when ultrasonic waves propagate through a fluid, the time it takes to pass between two points changes depending on the flow.

The disadvantages of this flow meter are: (1) If bubbles or foreign objects are present in the fluid in the ultrasonic propagation path, the ultrasonic waveform will be disrupted or disappear; If there is a drift in the flow, an error may occur in the transit time of the ultrasonic waves, resulting in poor measurement accuracy.

An object of the present invention is to provide an ultrasonic current meter that eliminates the above-mentioned drawbacks.For this purpose, the present invention amplifies and rectifies the received ultrasonic waves and converts them into analog values. The device was configured to perform the function of measuring the propagation time when the signal is within a predetermined level range for a predetermined amount of time, thereby achieving the intended purpose.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, on the pipe wall of the pipe line 1 through which the fluid to be measured flows,
Ultrasonic transmitter/receivers 2 and 3 face each other across the flow path,
They are installed on the upstream and downstream sides, respectively.

The transmitter/receiver 2 and 3 are each connected to a transmission switching unit 4, and the transmission/reception switching unit allows each to function as a transmitting side or a receiving side.

An analog conversion section 5, a transmission drive section 8, and a switching control section 9 are connected to the transmission/reception switching section 4, respectively.

A level determination section 6A and an edge detection section 10 are connected to the analog conversion section 5.

The level determination section 6 is connected to a sampling control section 7, a transmission driving section 8.1==, and a switching control section 9, respectively.

The transmission driving section 8 and the edge detection section 10 are each connected to a transmission time detection section 11.
and the switching control section 9 are each connected to an instruction recording section (not shown).

Next, the operation and effects of this embodiment configured as described above will be explained with reference to FIG. 1 and FIG. 2.

It is assumed that the transmission/reception switching unit 4 switches the transceiver 2 to transmit and the transceiver 3 to reception based on a signal from the switching control unit 9.

The drive signal of the transmitter 2 and the transmission drive unit 8 is 2 in Fig. 2a.
1 indicates the waveform of the peak value of the wave height of 1 drive unit signal).Continuous ultrasonic waves are transmitted.

This ultrasonic wave propagates through the fluid, and when received by the receiver 3, enters the analog conversion section 5 through the transmission/reception switching section 4.

The analog converter 5 amplifies the input ultrasonic wave, performs full-wave rectification, and converts the peak value of the wave height into an extracted analog value.

This analog value is shown at 30 in FIG.

A determining means comprising a level determining section 6 and a sampling control section 7 determines whether this analog value is within a reference level.

That is, the level determination section 6 has an upper limit value H1 and a lower limit value set in advance around the reception level when there are no bubbles, drifting, etc., and when the analog value 30 falls within the range, a signal is sent to the sampling control section 7. send.

When the sampling control unit 7 detects that the signal from the level determination unit 6 continues for a certain predetermined period of time, the sampling control unit 7 outputs a control signal to stop the transmission drive unit 8 via the level determination unit 6. It is sent to the transmission driver 8.

FIG. 2 Already, Wl has insufficient time within the reference level range, and W2. Since W3 is within the reference level range for a certain period of time or more, the control signal is output from the sampling control section 7 via the level determination section 6.

This signal is input to the transmission drive unit 8, and the transmission drive unit 8 temporarily stops the drive signal and stops the transmission of the transmitter 2 for a certain period of time.

This condition is indicated at 2-2 in FIG. 2a.

The change in the received signal caused by the stoppage of the transmission drive section 8 is detected by the transmission time detection means consisting of the edge detection section 10 and the transmission time detection section 11, and the time delay of the above-mentioned double conversion, that is, the transmission time is determined as follows. Detected.

That is, the edge 22ab at which the drive signal stops and the rising edge 22b at which the drive starts after a certain period of time are already 23a and 2 in FIG. 2, respectively, in the analog value of the received ultrasound.
It will look like 3b.

This stop edge 23at or the rising edge 2 of the start of transmission
3b is detected by the edge detection section 10, and upon receiving its timing output and the timing output of the 22al tab 22b from the transmission 7 drive section 8, the transmission time detection section 11 detects the stop edge 22.
The time difference Ati between a and 23a or the time difference Jt' between the rising edges 22b and 23b at the start of transmission is detected.

Since this time difference represents the time required for the ultrasonic wave to propagate in the flow direction in the fluid, the propagation time detection unit 1
The transmission time of the ultrasonic wave in a normal flow state in the direction of flow can be obtained by the time signal from 1 and the signal from the switching control unit 9 indicating that the transmission is from the transceiver 2.

The transmission time in the opposite direction to the flow direction is determined by the switching control section 9.
It is clear that the signal can be obtained in exactly the same manner as above by switching the transmitter/receiver 3 to transmit and the transmitter/receiver 2 to receive by the transmit/receive switching unit 4.

As detailed above, according to the present invention, the attenuation of ultrasonic waves propagated through a fluid and received is monitored, and if the attenuation becomes too strong due to air bubbles, foreign objects, etc., the measurement mode cannot be entered, and the ultrasonic waves are Since the measurement is performed only when the attenuation is in a normal state, it is possible to provide a highly accurate positional sonic current meter that is not wasted in measurement and can obtain a transmission time without error.

However, in the above embodiment, the ultrasonic waves from the pair of transceivers were used to monitor attenuation and measure the propagation time, but a pair of transceivers dedicated to each may be provided separately. It is best to monitor the attenuation with a pair of transceivers located slightly upstream.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the ultrasonic current meter according to the present invention → the embodiment, Fig. 2a is a time chart of the peak value of the wave height of the drive signal of the transmitter 1 drive section in Fig. 1, and Fig. 2 1 is a time chart of a received ultrasonic wave which is amplified and full-wave rectified by the analog converter shown in FIG. 1 and converted into an analog value by extracting the peak value of the wave height. 1... Conduit, 2, 3... Ultrasonic transceiver, 4...
Transmission/reception switching section, 5... Analog conversion section, 6... Level determination section, 7... Sampling control section, 8... Transmission driving section, 9... Switching control section, 10... Edge detection section ,1
1...Transmission time detection section.

Claims (1)

[Claims] 1. Ultrasonic transceivers are attached to the upstream and downstream sides of the fluid to be measured, with the flow path sandwiched between the pipe walls, and the ultrasonic transceivers transmit signals alternately according to commands from the switching control unit! a transmitter/receiver switching unit that switches to or receives continuous ultrasonic waves; a stone transmitter drive unit that causes one of the transmitters and receivers to transmit continuous ultrasonic waves; and amplifies and full-wave rectifies the ultrasonic waves received by the other of the transmitters and receivers to obtain the peak of the wave height. an analog conversion unit that converts the extracted value into an analog value; a determination unit that detects that the output of the analog conversion unit is within a predetermined range for a certain period of time and stops the transmission drive unit; and the determination unit detecting a change in the received signal caused by the stoppage of the transmitter 7 drive unit,
An ultrasonic current meter characterized by comprising: transmission time detection means for detecting a time delay from a change in the signal of the transmission drive unit that caused the change.