JPS61104276A - System for transmitting and receiving ultrasonic pulse - Google Patents

Abstract

PURPOSE:To remote the effect of an interference wave by the averaging effect of propagation time difference, by selectively outputting either one of positive and negative polarity transmission signals and setting the point of time when a receiving signal arrived a predetermined change point as the arrival time of an ultrasonic signal. CONSTITUTION:A transmission signal output means 10 is constituted of a pulse generation circuit 11, a drive circuit 12, a transmitting and amplifying circuit 13 consisting of transistors 13A, 13B and a transmission terminal 14 connected to ultrasonic transmitter receivers 2, 3 through a transmission and reception change-over circuit 4. This ultrasonic signal output means 10 selectively outputs either one of positive and negative polarity ultrasonic signals taking the relation of mutually inverse polarity according to preset sequence or random sequence and allows said signal to propagate through the medium to be measured of a flow pipe 1 to selectively output the same to ultrasonic signal detection means 20 and the point of time, when the ultrasonic signal arrived a predetermined change point, is set as the arrival time of the ultrasonic time regardless of the polarity of the ultrasonic wave propagated through the medium to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a transmission/reception signal system for ultrasonic pulse signals in ultrasonic flowmeters, level meters, thickness meters, and the like.

[Technique of promoting rice]

FIG. 5 is a block diagram of a conventional external wall transmission type ultrasonic flow meter. In Fig. 5, 1 is a flow tube through which fluid flows in the direction of the arrow ■, 2.3 is an ultrasonic transducer that converts the ultrasonic signal into electricity-sound 9 and acoustic-electricity, and 4 is the ultrasonic signal that converts the ultrasonic signal into an ultrasonic wave. Transducer 2 to 3 or ultrasonic transducer 5 to 2
, that is, a transmitting/receiving switching circuit that switches the ultrasonic signal to propagate in the forward direction along the fluid flow or in the reverse direction against the fluid flow; 5 is a transmitting circuit; 6 is a receiving circuit; 7 is an ultrasonic signal and A signal processing circuit 8 measures the time of one cycle in which the corresponding electric signal propagates to the transmitting circuit 5 or the receiving circuit 6 multiple times, and outputs a signal corresponding to the fluid flow velocity based on the measured propagation time. A display 9 displays the results, and a timer 9 outputs a 1 minute pulse to control the operation of each part of this ultrasonic flowmeter. Note that the output of the transmitting circuit 5 and the input of the receiving circuit B are electrical signals, and the signals propagating within the flow tube 1 are ultrasonic signals.

To explain the operation of such a conventional external wall transmission type ultrasonic flowmeter, first, a signal output as a transmission wave from the transmission circuit 5 is input to the ultrasonic transducer 3 via the transmission/reception switching circuit 4, and is reversely transmitted through the fluid. propagates in the direction and reaches the ultrasonic receiver 2,
Further, the signal is input to the receiving circuit 6 as a received wave via the transmission/reception switching circuit 4. After this ultrasonic signal propagates in the opposite direction multiple times, when the transmission/reception switching circuit 4 is switched, the signal output from the transmission circuit 5 is input to the ultrasonic transducer 2 via the transmission/reception switching circuit 4. It propagates in the fluid in the forward direction, reaches the ultrasonic transducer 6, and is further input to the transmission/reception switching circuit 4 and the receiving circuit B. The propagation of the ultrasound signal wave in the head direction is also performed multiple times.

The signal processing circuit 7 detects the flow rate, number, amount, etc. of the fluid using a sing-around method, a PLL method, a time difference method, etc., based on the forward and reverse propagation times of the ultrasonic signal waves.

Next, FIG. 6 is a diagram showing an example of the waveforms of the above-mentioned transmitted waves and received waves. The transmission wave output from the transmission circuit 5 has a waveform as shown in FIG. 6(&) or FIG. 6(b)K. On the other hand, the received wave ri input to the receiving circuit B
The waveform becomes as shown in FIG. 6(c) K.

The ultrasonic signal is repeatedly reflected, refracted and diffused at each boundary between the ultrasonic transducer 2 or 3 and the tube wall, and between the tube wall and the fluid.
Since the ultrasonic signal reaches the ultrasonic transducer 2 or 6 through a complicated propagation path, K also disappears immediately after the ultrasonic signal reaches the ultrasonic transducer 2 or 7 through the complicated propagation path. The receiving circuit 6 is superimposed on the transmitted wave that is sent out next.
The received wave that is input to the transmitter is superimposed on the signal wave that should originally be received through the complicated propagation path as described above, and on the transmitted wave that is sent out next. This will cause an error in the signal propagation time, but
The received wave is a composite wave that is composed of a signal wave whose generation time is almost the same as that of the signal wave, and which has almost the same frequency band as the interference wave (hereinafter referred to as the interference wave). cannot be removed. The degree of influence of this interference wave varies depending on the S/N ratio between the signal wave and the interference wave, the phase difference between the forward and reverse ultrasonic signals, and the like. For example, if the frequency of the ultrasonic temporary signal is IMHz% and the phase difference is 0. The diameter of tube 1 is 5
In the case of 0 deafness and the fluid flow velocity of im/s, the propagation time difference when ultrasonic signals are propagated in both directions is approximately 40 nS. Here, if the S/N ratio between the signal wave and the interference wave is 40 dB, an error of 0.8 nS will occur, so 0.8/40=0.
02, resulting in a measurement error of approximately 2%. Further, it is extremely difficult to set the signal wave to interference wave O8N ratio to 40 dB, and the measurement error becomes 2% or more. Furthermore, when the diameter of the flow tube 1 is small or when the flow rate of the fluid is slow, measurement errors will increase.

[Problem that the invention attempts to solve]

In order to avoid the shadow 9 of such interference waves, conventionally, the interval at which the transmitted waves are outputted, that is, 1-! By making the period of the 7° cycle sufficiently long9, the interference waves generated in the cycles before the cycle in which the transmitted wave dies out are extinguished.

However, by lengthening the period of one cycle, the number of times the propagation time is measured per unit time is reduced, and it becomes time-consuming to measure the flow velocity of the fluid.

The present invention was made for the purpose of solving the above problems.
The present invention provides an ultrasonic pulse transmission/reception method that can eliminate the influence of interference waves without increasing the period of one cycle.

[Means for solving problems]

Therefore, in the present invention, one of the positive polarity ultrasonic signal and the negative polarity ultrasonic signal, which have opposite polarity to each other, is selectively outputted according to a preset sequence or a random sequence. Regardless of the polarity of the ultrasonic signal selectively outputted from the ultrasonic signal output means and the ultrasonic signal output means and propagated in the medium to be measured, it is determined that the ultrasonic signal has reached a predetermined change point. Ultrasonic signal detection means is provided to detect the ultrasonic signal.

[For Western]

In the ultrasonic pulse transmission and reception method of the above configuration, the ultrasonic signal output means transmits either a positive polarity ultrasonic signal or a negative polarity ultrasonic signal having opposite polarities to each other in a preset sequence or randomly. The ultrasonic signal is selectively outputted according to the sequence, propagated into the medium to be measured, and the ultrasonic signal detection means is selectively outputted, and the ultrasonic signal reaches a predetermined change point regardless of the polarity of the ultrasonic signal propagated in the medium to be measured. The time when the ultrasonic signal reaches the ultrasonic signal is defined as the arrival time of the ultrasonic signal.

〔Example〕

Hereinafter, embodiments of the present invention will be explained in detail with reference to the accompanying drawings. Fig. 1 is a block circuit diagram of the main parts of an ultrasonic flowmeter to which the ultrasonic pulse signal transmission/reception method according to the present invention is applied. be. In FIG. 1, 10 selects either a positive polarity signal tube or a negative polarity signal, which have opposite polarities to each other, according to a preset sequence or a random sequence, and outputs it as a transmission wave. Transmission signal output means includes a pulse generation circuit 11, a drive circuit 12,
Transmission amplifier circuit 15 consisting of transistors 13A and 15B
and a transmission terminal 14 connected to the ultrasonic transducer 2.3 via the transmission/reception switching circuit 4 shown in FIG. 20 is output from the transmission signal output means 10 and propagates in the fluid (measured medium) of the flow tube 1 shown in FIG.
The reception signal detecting means detects the arrival time of a signal input as a reception wave, and the reception terminal 21 and the terminals 0UT1 and 0UT1 output signals of the same polarity and opposite polarity (opposite phase) with respect to the input reception wave. 0UT2, a received wave polarity switching circuit 26 consisting of analog switches 23A and 23B, which selects and outputs one of the received waves of opposite polarity output from the amplifier circuit 22, and an input terminal INI. and IN2, and a comparison circuit 25 whose comparison reference level is set to OVK and which detects the zero-crossing point of the received wave. Reference numeral 60 controls the drive circuit 12 and the received wave polarity switching circuit 26 to select transmitted waves of opposite polarity from the ultrasonic signal output means 10 according to a predetermined sequence, and changes the polarity of the received wave according to the polarity of the transmitted waves. This is a controller that switches the 40 is a signal processing circuit which calculates the rise time t of the transmission wave output from the transmission signal output means 10 - the sending time of the transmission signal, and the zero loss point passing time of the reception wave input to the reception signal detection means 20. The propagation time is the arrival time of the received signal, and the difference between the arrival time and the sending time, and the propagation time is when the ultrasonic signal is propagated multiple times in the backward and forward directions! Time difference Δt between Bltu and td (Δt=tu−td
), a signal corresponding to the fluid flow velocity is output using the sing-around method, PLL method, or time difference method. 9 is a timer that controls the operation timing of each part.

The transmission signal output means 10 turns on the transistor 13A and turns off the transistor 13B to output a positive transmission signal, turns off the transistor 13A, and turns off the transistor 1.
3B is turned off and a negative polarity transmission signal is output. Further, the received signal detection means 20 connects the analog switch 26A to terminal 0.
On the UTi side, switch the analog switch 23B to the terminal 0UT2 side, apply the received ultrasonic signal to the amplifier circuit 24, and switch the analog switch 23A to the terminal OUT Z side, switch the analog switch 23Bti to the terminal 0UTI (11, 11). The received signal is inverted and applied to the amplifier circuit 24.

By the way, as described above, regardless of whether the transmitted wave is propagated in the forward or reverse direction, the received wave inputted to the received signal detection means 20 is different from the transmitted wave T as shown in FIG. A composite wave R is obtained by superimposing the signal wave S and the interference wave N. The effect of the interference wave N is, for example, when the transmitted wave propagates in the opposite direction, the propagation time is delayed by a time α compared to the propagation time tu when there is no influence of the interference wave N (see Fig. 2 (λ)). ).

Also, if the transmitted wave is propagated in the forward direction &, the propagation time is made faster by α compared to the propagation time tdK when there is no influence of the interference wave N (see FIG. 2(b)). Therefore, the propagation time difference Δt, which is the difference between the propagation time tu when the ultrasound is propagated in the reverse direction and the propagation time td when the ultrasound is propagated in the forward direction, is (tu - td + 2α). This causes an error of only 2α.

Therefore, in the present invention, the transmission signal output means 10 selects and transmits either a positive polarity transmission signal or a negative polarity transmission signal, which have opposite polarities to each other, according to a preset sequence or a random sequence. Output as a wave. The received signal detection means 20 switches the received wave polarity switching circuit 23 according to the polarity of the transmitted wave, and detects a specific point of the received wave, for example, a zero crossing point when the received wave changes from positive to negative. Further, the signal processing circuit 40 measures the propagation time difference obtained by propagating the ultrasonic signals transmitted and received in the reverse direction and the forward direction multiple times as described above, and averages the measurements. Obtain the propagation time difference with wave effects removed.

Assume that the disturbance is due to the residual image of the transmitted wave from the previous cycle, and either a positive ultrasonic signal or a negative ultrasonic signal, which have a positive polarity relationship that is opposite to each other. , shows the propagation time difference and the average of the propagation time difference when selectively outputting according to various 7-cases.

Fist Conventional Sequence In Table 1, the first sequence is the conventional one.9
, the propagation time difference is Δt+2α, and the average thereof is Δt+2α, so the error time 2α is not removed. In addition, the second sequence has positive polarity and
The polarity of the transmitted wave is alternately changed such as negative polarity, positive polarity, etc., the propagation time difference is Δt-2α, the average thereof is Δt-2α, and the error time -2α remains without being removed. Furthermore, the third sequence is positive polarity, positive polarity, negative polarity, negative polarity,
The polarity of the transmitted wave is changed every two times, such as positive polarity, positive polarity, etc., and the propagation time difference is Δt±2a, the average thereof is Δt, and the error time is removed.

The polarity of the transmitted wave in the third sequence is appropriately selected. By doing so, it is possible to eliminate the influence of interference waves caused not only by the previous transmission but also by the previous transmission. However, by randomly selecting the polarity of the transmitted waves, the influence of interference waves caused by various causes can be removed by an averaging effect.

Next, FIG. 3 is a block circuit diagram showing another embodiment of an ultrasonic flowmeter to which the ultrasonic pulse signal transmission/reception method according to the invention is applied, and only the main parts are shown.

In FIG. 3, parts that perform the same functions as those in FIGS. 1 and 5 are designated by the same reference numerals, and their explanations will be omitted. 15 is a switching circuit that switches the polarity of the transmitted wave according to a signal from the controller 50, and 26 is a switching circuit that switches the @note of the received wave. Both of the switching circuits 15 and 26 use DPDT type semiconductor switches.

In this embodiment, polarity switching circuits 15 and 26 using DPDT-type semiconductor switches switch the polarity of the transmitted wave and the receiving section, and the transmitting circuit 5 and There is an advantage that the receiving circuit 6 can be used.

Further, FIG. 4 is a block circuit diagram showing another embodiment of an ultrasonic flowmeter to which the ultrasonic pulse signal transmission/reception method according to the invention is applied, and only the receiving portion is shown.

Note that in FIG. 4, parts that perform the same functions as those in FIG.

In this embodiment, the polarity of the received wave is not reversed, and the polarity of the received wave is not reversed.
A comparison circuit 27 is used to detect the cross point when the received wave of negative polarity changes from negative to positive, and a comparison circuit 28 is used to detect the cross point when the received wave of negative polarity changes from negative to positive. There is. Strobe terminals 5TBi and 5TB2 are connected to comparator circuits 27 and 28U, respectively.
The voltage comparison operation is performed only when the -p signal is applied.

〔Effect of the invention〕

As explained above, according to the present invention, either one of the transmission signals of positive polarity or negative polarity having opposite polarity to each other is selectively outputted according to a preset sequence or a random sequence, and the selectively outputted transmission signal is transmitted. Regardless of the signal note, if the arrival time of the ultrasonic signal is the time when the received signal reaches a predetermined change point, it is possible to eliminate the influence of interference waves by the average effect of the n propagation time differences. can.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of the main parts of an ultrasonic flowmeter to which the ultrasonic pulse signal transmission/reception method according to the invention is applied, and FIG. 2 is a waveform diagram showing an example of the waveforms of transmitted waves and received waves.
Figures 6 and 4 (1) are block circuit diagrams showing other embodiments of the ultrasonic flow meter to which the ultrasonic pulse signal transmission/reception method according to the invention is applied; 6 is a waveform diagram showing an example of the waveforms of the transmitted wave and the received wave. 10... Transmission signal output means, 11... Pulse generation circuit, 12. ...Drive circuit, 13 Transmission amplifier circuit, 1
4... Transmission terminal, 20... Received signal aspect ratio means, 2
1... Receiving terminal, 22... Receiving power increase circuit, 23.2
6...Polarity switching circuit, 24...Amplification circuit, 25,2
7.28--Comparison road, 29...-Or gate, 60
...Controller, 40...Signal processing circuit. Representative Patent Attorney Sanro Kimura Figure 3, Figure 4, Figure 5! Figure 6 1, Indication of cattle Patent Application No. 1982-225668 2, Name of the invention Ultrasonic pulse transmission/reception method・1 Ya (338) Tokyo Keiki Co., Ltd. (Name i 4.1 (Embedded 7, Contents of the amendment (1) The "Claims" of the specification will be amended as shown in the attached sheet. (2) "1st" in the fourth line from the bottom of page 12 of the specification will be corrected to "". (3) Figures 1 and 4 of the drawings are corrected according to the attached drawings.Claims: Ultrasonic signals of positive polarity and ultrasonic signals of negative polarity, which have opposite polarity to each other, are arranged in a preset manner. An ultrasonic signal output means for selectively outputting and propagating in a measured medium according to a sequence/sequence random sequence, regardless of the polarity of the ultrasonic signal selectively output and propagated in the measured medium,
An ultrasonic pulse transmitting/receiving method comprising ultrasonic signal detection means that determines the arrival time when the ultrasonic signal reaches a predetermined change point.

Claims (1)

[Claims] selectively outputting either a positive polarity ultrasonic signal or a negative polarity ultrasonic signal having opposite polarities according to a preset sequence or a random sequence;
an ultrasonic signal output means for propagating into a medium to be measured; and a point at which the ultrasonic signal reaches a predetermined change point, regardless of the polarity of the ultrasonic signal selectively output and propagated in the medium to be measured. 1. An ultrasonic pulse transmission/reception method characterized by comprising: ultrasonic signal detection means for detecting time.