JPH11148848A - Method for judging pulse skip in measuring ultrasonic wave propagation time - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for judging pulse skip which judges whether a pulse skip has occurred or not. SOLUTION: A transmitter and a receiver are provided with an interval in a medium, and the ultrasonic wave transmitted from the transmitter is detected with the receiver, and the propagation time of ultrasonic wave in a medium is measured based on a time point when the level of a reference pulse P1 in a pulse train forming a reception oscillation wave reaches a threshold value VTH. Here, the measurement is continuously performed by a plurality of times to obtain a maximum value and a minimum value of the propagation time. When the difference between the maximum value and the minimum value corresponds to the oscillation cycle of a ultrasonic wave element, a pulse skip wherein a next pulse P3 skips the reference pulse P12 to reach the threshold value VTH is judged to have occurred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a pulse jump in measuring an ultrasonic propagation time used in an ultrasonic flow velocity measuring method for measuring the flow velocity of a gas or other fluid using ultrasonic waves, for example. More specifically, the present invention relates to a pulse jump determination method for determining whether or not the relationship between a reference pulse for determining an ultrasonic wave propagation time in a pulse train forming a received vibration wave and a threshold value is out of order.

[0002]

2. Description of the Related Art An ultrasonic flow velocity measuring method as described above is arranged such that a transmitter and a receiver are arranged on an upstream side and a downstream side of a measuring medium, respectively, and a driving pulse is applied to an ultrasonic transmitting element of each of the transmitters. To generate and transmit ultrasonic waves to each other, receive the transmitted ultrasonic waves with each other, and measure the flow velocity based on the difference in the propagation time of the ultrasonic waves obtained from the comparison of each received wave How to Such a flow velocity measurement is performed, for example, when obtaining a flow rate of a gas or the like.

Since the ultrasonic element is a secondary vibration system and can be considered as a secondary vibration circuit composed of capacitance and inductance, the vibration waveform of the received wave is shown in FIG.
As shown in (a), the amplitude gradually increases and then attenuates. The time point t1 at which the predetermined reference pulse P1 of the pulse train forming the positive half wave of the received wave reaches the threshold value VTH is regarded as the time point at which the transmitted wave arrives at the receiver, and the propagation of the ultrasonic wave is performed. The time is fixed.

[0004]

In the ultrasonic flow velocity measurement as described above, the reception waveform of the ultrasonic wave may be attenuated due to an increase in the flow velocity or the like. Then, when the degree of attenuation increases, as shown in FIG.
A pulse jump may occur in which the peak voltage value of 1 falls below the threshold value VTH, exceeds the reference pulse P1, and the next pulse P3 reaches the threshold value VTH.

However, in this case, the time point t2 at which the pulse P3 following the reference pulse P1 reaches the threshold value VTH is regarded as the time point at which the transmitted wave reaches the receiver. There is a drawback that an error is generated and, as a result, high-precision flow measurement or the like cannot be performed.

The present invention has been made to solve such a drawback, and a pulse jump for determining whether or not the above-described pulse jump has occurred in the measurement of the ultrasonic propagation time. It is an object to provide a determination method.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to dispose a transmitter and a receiver separately in a medium, receive the ultrasonic wave transmitted from the transmitter by the receiver, and receive the ultrasonic wave. When measuring the propagation time of the ultrasonic wave in the medium based on the time when the level of the reference pulse in the pulse train forming the wave reaches the threshold value, the maximum value of the propagation time by performing the measurement continuously plural times. A minimum value is obtained, and if the difference between the maximum value and the minimum value corresponds to the vibration period of the ultrasonic element, a pulse jump exceeding the reference pulse and reaching the threshold value of the next pulse is generated. This is solved by a method of determining a pulse jump of the ultrasonic wave propagation time, characterized in that

According to the above configuration, the minimum value of the propagation time is a value obtained based on the relationship between the reference pulse and the threshold value, and the maximum value is a pulse which causes a pulse jump and the next pulse of the reference pulse and the threshold value. Is a value obtained based on the relationship with Since the reference pulse and the next pulse are out of phase by an amount corresponding to one oscillation cycle of the received wave, the difference between the maximum value and the minimum value of the propagation time is substantially equal to the cycle of the received wave.
Since the oscillation cycle of the received wave is equal to the oscillation cycle of the ultrasonic element, when the difference between the maximum value and the minimum value of the propagation time is substantially equal to the oscillation cycle of the ultrasonic element, it is determined that a pulse jump has occurred. be able to.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram of an ultrasonic flow velocity measuring device for carrying out an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a conduit through which a fluid such as gas flows in the direction of an arrow. In the pipe 1, the transducers 2 and 3 are arranged at a predetermined distance on the upstream side and the downstream side in the flow direction.

Each of the transducers 2 and 3 serves as both a transducer and a transducer, and includes an ultrasonic transmitting / receiving element (not shown) composed of a vibrator. The ultrasonic transmitting / receiving element is driven and vibrated by the driving pulse from the pulse generation circuit 4 to generate and transmit an ultrasonic wave, while receiving the transmitted ultrasonic wave and transmitting and receiving the ultrasonic wave. The received wave when vibrated is output from the amplifier circuit 5 as an electric signal.

The propagation time until the ultrasonic wave transmitted from the upstream transducer 2 in the forward direction to the flow is received by the downstream transducer 3 and the flow from the downstream transducer 3 to the flow On the other hand, since the difference from the propagation time until the ultrasonic wave transmitted in the opposite direction is received by the upstream transducer 2 is related to the flow velocity, the flow velocity of the fluid is measured by obtaining the propagation time difference. It has been done. In FIG. 1,
Reference numeral 6 denotes a switching circuit for switching the connection between each of the transducers 2 and 3, the pulse generator 4 and the amplifier 5, and firstly, the pulse generator 4 and the upstream transducer 2, the downstream transducer 3 and the amplifier 5 And after measuring the propagation time from the upstream side to the downstream side, the operation of the switching circuit 6 causes the pulse generation circuit 4 and the downstream side transducer 3, and the upstream side transducer 2 and the amplification circuit 5 to connect with each other. The connection time is switched so that the propagation time from the downstream side to the upstream side is measured.

As shown in FIG. 2A, the oscillation waveform of the received wave output from the amplifier circuit 5 has a shape that gradually increases in amplitude and then attenuates. In this embodiment, the amplitude is increased to the fourth wave after reception and then attenuated, and the third pulse of the pulse train composed of the positive half-wave is set as the reference pulse P1.

In FIG. 1, reference numeral 7 denotes a comparison circuit which compares a predetermined threshold value VTH with the voltage level of the reference pulse P1, and outputs a reaching signal when the voltage level of the reference pulse P1 reaches the threshold value. While calculating the propagation time from the transmission of the ultrasound until the arrival signal is output,
This is an arithmetic circuit that calculates the difference between the maximum value and the minimum value and the average value when the measurement of the propagation time is repeated a plurality of times continuously.

The threshold value VTH is set to a predetermined value higher than the peak voltage value of the pulse P2 immediately before the reference pulse P1 in the received wave and lower than the peak voltage value of the reference pulse P1. Therefore, normally, the reference pulse P1 of the received wave crosses the threshold value VTH, and the arrival of the received wave is determined at the crossing timing t1. However, when the flow velocity increases, the reception waveform of the ultrasonic wave is attenuated as shown in FIG. 2 (b), and when the degree of attenuation increases, the pulse jump occurs as described above.

Therefore, the presence or absence of a pulse jump is determined as follows. That is, the arithmetic circuit 8 calculates the minimum value, the maximum value, and the average value of a plurality of continuous (eg, 50) measurement values at a predetermined time during the flow velocity measurement.
Thus, when no pulse jump occurs, the propagation time is obtained based on the timing t1 at which the voltage level of the reference pulse P1 reaches the threshold value VTH, and this is the minimum value. On the other hand, in the state where the pulse jump has occurred, FIG.
As shown in (b), the propagation time is obtained based on the timing t2 when the voltage level of the pulse P3 following the reference pulse P1 reaches the threshold value VTH, and this is the maximum value. The difference between the maximum value and the minimum value is equal to the time T from the time when the reference pulse P1 reaches the threshold value VTH until the time when the next pulse P3 reaches the threshold value VTH, as shown in FIG. The time T is substantially equal to the oscillation period of the received wave.

On the other hand, since the received wave oscillates at a cycle corresponding to the frequency of the ultrasonic element, this cycle can be easily known. For example, in the case of a 40 KHz ultrasonic element, the oscillation period of the received wave is 25 μm.

Therefore, if the difference between the maximum value and the minimum value of the propagation time obtained as described above is substantially equal to the oscillation period of the received wave (25 μm in the above example), it is determined that a pulse jump has occurred. be able to. In addition, since the average value of the propagation time changes according to the magnitude of the frequency of the pulse jump, the frequency of the pulse jump can be estimated based on the average value of the propagation time obtained by the arithmetic circuit 8. it can.

In this way, the presence / absence and frequency of occurrence of a pulse jump can be ascertained, and the measurement data obtained by ordinary measurement can be corrected based on the information, so that a highly accurate ultrasonic flow velocity measurement can be performed. Thus, the flow velocity measurement (flow rate measurement) of the fluid with high accuracy can be performed.

[0020]

As described above, according to the present invention, a transmitter and a receiver are separately arranged in a medium, the ultrasonic wave transmitted from the transmitter is received by the receiver, and the receiving vibration When measuring the propagation time of the ultrasonic wave in the medium based on the time when the level of the reference pulse in the pulse train forming the wave reaches the threshold value, the maximum value of the propagation time by performing the measurement continuously plural times. A minimum value is obtained, and if the difference between the maximum value and the minimum value corresponds to the vibration period of the ultrasonic element, a pulse jump exceeding the reference pulse and reaching the threshold value of the next pulse is generated. Therefore, it is possible to easily determine whether or not a pulse jump has occurred, and it is possible to measure the ultrasonic wave propagation time with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an ultrasonic flow velocity measuring device for explaining an embodiment of the present invention.

FIG. 2A is a waveform diagram of a received wave when a pulse jump does not occur, and FIG. 2B is a waveform diagram of a received wave when a pulse jump occurs.

[Explanation of symbols]

 2, 3 ... transducer 4 ... pulse generation circuit 5 ... amplification circuit 7 ... comparison circuit 8 ... operation circuit P1 ... reference pulse VTH ... threshold

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takaomi Raft 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi Inside Osaka Gas Co., Ltd. Kansai Gas Meter Co., Ltd. (72) Inventor Akio Kono 2-10-16 Higashikobashi, Higashi-Nari-ku, Osaka-shi Kansai Gas Meter Co., Ltd. (72) Inventor Tetsuya Yasuda Kansai Gas Meter Co., Ltd. 2-10-16 Higashiobashi, Higashinari-ku, Osaka

Claims (1)

[Claims] 1. A transmitter and a receiver are spaced apart in a medium,
The ultrasonic wave transmitted from the transmitter is received by the receiver, and the propagation of the ultrasonic wave in the medium based on the point in time when the level of the reference pulse in the pulse train forming the received vibration wave reaches a threshold value When measuring time, the measurement is performed a plurality of times continuously to determine the maximum value and the minimum value of the propagation time, and when the difference between the maximum value and the minimum value corresponds to the vibration cycle of the ultrasonic element, A pulse jump determination method for ultrasonic propagation time, wherein it is determined that a pulse jump exceeding the reference pulse and the next pulse reaches a threshold value has occurred.