JPH0361892B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic flowmeter, particularly an ultrasonic transducer that is disposed facing a pipe wall forming a flow path at a fixed angle. The present invention relates to an ultrasonic flowmeter that determines the flow velocity or flow rate from the ultrasonic propagation time between the transducer and the transducer.

2. Description of the Related Art So-called ultrasonic flowmeters that measure flow velocity and flow rate using ultrasonic waves are well known and are actually used in water supply and sewage systems, hydroelectric power plants, and the like.

The principle of lateral determination of this ultrasonic flowmeter is based on the fact that when the propagation speed of sound waves in a flowing fluid is propagated in the direction of the flow, the flow velocity becomes apparently faster, and in the opposite direction, it becomes slower. , the flow velocity in the pipe is v, the sound velocity in the stationary fluid is c, and the distance L
When a transducer is placed at _{two points} that are separated by a
Since the time t ₂ for the ultrasonic wave emitted from the point to reach the upstream point A is t ₂ = L(c-v) and c≫v, calculate t ₂ - t ₁ = 2Lv/c ² , the flow velocity v is determined by determining this time difference t ₂ −t ₁ .

Therefore, the above-mentioned time difference t ₂ −t ₁ is very short, and it is very difficult to accurately determine this time difference. That is, in the conventional system, the transducers are a pair, each of which is a vibrating body with its own natural frequency. Therefore, even if an oscillation signal is applied to the transmitter, there is a time delay until the steady state is reached.

However, since ultrasonic waves in a medium attenuate exponentially with distance, in a large-diameter flowmeter where the distance between the transmitter and receiver is large, the sound pressure on the receiver side becomes extremely low. In addition, when the sound pressure-voltage conversion efficiency is taken into consideration, the voltage value becomes several tens of decibels or more, and therefore, the received signal obtained by receiving the signal from the transmitter by the receiver is extremely small. Furthermore, since there is a time delay in the receiver as well as a time delay in the transmitter, the received signal increases slowly, and the detection level of the signal used to calculate t ₁ and t ₂ becomes unstable.

The present invention has been made in view of the above-mentioned circumstances, and is particularly intended to accurately determine the propagation time of ultrasonic waves in an ultrasonic flowmeter, thereby improving measurement accuracy.

Figures 1 and 2 are signal wave diagrams for explaining the measurement principle of the present invention. Figure 1 is a signal waveform diagram of the ultrasound emitted from the ultrasound transmitter, and Figure 2 is
This is a signal waveform diagram of ultrasonic waves received by an ultrasonic receiver. In the illustrated example, there are two pairs of ultrasonic transducers, and the ultrasonic wave shown in FIG. 1a is emitted from the transmitter side. is received by the receiver as an ultrasonic wave with a waveform as shown in Fig. 2a, while the ultrasonic wave shown in Fig. 1b emitted from the transmitter side is received by the receiver as an ultrasonic wave with a waveform as shown in Fig. 2a. It is received as an ultrasonic wave with a waveform as shown in b. Thus, the two ultrasonic waves (FIG. 1 a and b) emitted from the transmitter side have the same rising phase and amplitude, but different frequencies. Note that FIG. 1c shows a waveform when the ultrasonic waves shown in FIGS. 1a and 1b are added. The ultrasonic waves emitted by the transmitter as described above propagate through the fluid to be measured and reach the receiver, but the output signal waveform of each receiver has a time delay at the rise of the receiver. etc., as shown in Figure 2 a and b, respectively, and when these two signals are added together, the result is as shown in Figure 2 c, which reaches a singular level P after a predetermined time has elapsed from the start of reception, but this singular level The time when P appears is always a certain period of time after the start of reception. Therefore, by measuring the time from the time when the ultrasonic wave is emitted on the transmitter side to the time when the singular level appears, it is possible to measure the time that the ultrasonic wave propagates in the fluid to be measured, and it is possible to measure the time during which the ultrasonic wave propagates through the fluid to be measured. Therefore, the ultrasonic propagation time in the fluid to be measured can be accurately determined.

FIG. 3 is a diagram showing an embodiment of an ultrasonic flowmeter according to the present invention constructed based on the measurement principle as described above. In the figure, 1 is a trigger circuit, 2 and 3 are oscillators, and 4 and 5 are ultrasonic flowmeters. Sonic wave transmitter, 6 and 7 are ultrasonic wave receivers, 8 and 9 are amplifiers, 10 is an adder, 11
12 is a waveform shaping circuit, 12 is a flip-flop circuit,
13 is a clock pulse generator, 14 is a gate circuit, 15 is a counter, and 20 is a flow path tube.As shown in the figure, the flow path tube 20 has a wall having a fixed angle with respect to the flow path. Two pairs of ultrasonic transducers 4, 6 and 5, 7 are arranged facing each other,
For example, the ultrasonic signal shown in FIG. 1a is emitted from the transmitter 4, the ultrasonic signal shown in FIG. 1b is emitted from the transmitter 5, and the ultrasonic signal shown in FIG. The ultrasonic wave from the wave transmitter 5 is received by the wave receiver 6, and the ultrasonic wave from the wave transmitter 5 is received by the wave receiver 7. Therefore, in the present invention, the distance L ₁ between the ultrasonic transmitter 4 and the receiver 6 and the distance L 2 between the ultrasonic transmitter 5 and the receiver ₇ are completely equal. These two pairs of ultrasonic transducers are arranged as follows.
Both ultrasonicators 4 and 5 have the same rising phase and amplitude as shown in FIGS. 1a and 1b, and
Ultrasonic waves having different frequencies are emitted, but the rising phases of both ultrasonic waves are kept in the same phase by activating both oscillators 2 and 3 simultaneously by the trigger circuit 1. The trigger circuit 1 simultaneously activates the oscillators 2 and 3 as described above, turns on the SR flip-flop circuit 12, opens the gate circuit 14, and activates the clock pulse generation circuit 1.
3, the counter 15 starts counting clock pulses. On the other hand, the ultrasonic waves emitted from the ultrasonic transmitters 4 and 5 as described above are received by the ultrasonic receivers 6 and 7, respectively, and the adder 10
The signals are added by , and converted into a signal as shown in FIG. 2c. In the output signal of the adder 10, a singular level point as shown by P in FIG.
If it is turned off, the counter 15 will have measured the time from ultrasonic transmission to generation of the singular level. Since the time t from reception to generation of the singular level is constant as described above, the propagation time of the ultrasonic wave in the fluid to be measured can be determined from the count value of the counter 15. In addition, although the embodiment described above measures only the flow of the fluid to be measured in one direction, the present invention is not limited to the above embodiment.
For example, it is possible to further improve the above embodiment to configure a single-around type ultrasonic flowmeter. In that case, the output signal of the waveform shaping circuit 11 can be used to switch the ultrasonic transducer and (In other words, the outputs of the oscillators 2 and 3 are input to the receivers 6 and 7, and the receivers 6 and 7 are used as transmitters, and the transmitters 4 and 5 are used as receivers, and the receivers 6 and 7 are used as transmitters. The outputs of the amplifiers 4 and 5 are input to the amplifiers 8 and 9 respectively), and the trigger circuit 1 is activated.
Measurements can be taken alternately for forward and reverse flows of the fluid to be measured.

As is clear from the above description, according to the present invention, it is possible to provide an ultrasonic flowmeter with a simple configuration and high measurement accuracy.

[Brief explanation of drawings]

1 and 2 are signal waveform diagrams for explaining the operating principle of the present invention, FIG. 1 is a waveform diagram of transmitted ultrasound waves, FIG. 2 is a waveform diagram of received ultrasound waves, Third
The figure is a configuration diagram showing an embodiment of the present invention. 1... Trigger circuit, 2, 3... Burst oscillator, 4, 5... Ultrasonic wave transmitter (receiver) device, 6, 7...
...Ultrasonic wave receiver (transmitter), 8, 9...Amplifier, 1
0... Adder, 11... Waveform shaping circuit, 12...
SR flip-flop circuit, 13... clock pulse generation circuit, 14... gate circuit, 15... counter.

Claims (1)

[Claims] 1. An ultrasonic transducer is provided on a pipe wall that forms a flow path and is disposed facing the flow path at a fixed angle, and a In an ultrasonic flowmeter that measures a flow rate from the propagation time of a propagating ultrasonic wave, a plurality of the ultrasonic transducers are arranged with the same ultrasonic propagation distance, and each of the transmitters has the same rising phase, Ultrasonic waves of the same level and different frequencies are emitted, the detection signals of each receiver are added on the receiver side, the time when the added value reaches a predetermined level is detected, and the predetermined value is determined from the rise time. An ultrasonic flowmeter characterized in that the flow rate of the fluid flowing in the flow path is measured based on the time it takes to reach a level. 2. An ultrasonic transducer is disposed on a pipe wall forming a flow path facing the flow path at a fixed angle, and an ultrasonic burst signal is transmitted between the transducer and the ultrasonic wave transmitter. In an ultrasonic flowmeter that calculates the flow rate from the difference in propagation time of ultrasonic waves in the forward and reverse directions of the flow by transmitting based on these received signals,
A plurality of pairs of the above-mentioned ultrasonic transducers are arranged, the ultrasonic propagation distance and signal level of these transducers are kept constant, and ultrasonic signals of different frequencies with the same phase are applied to each transmitter. An ultrasonic flowmeter characterized in that the ultrasonic flowmeter transmits data using a received beat signal.