JPH0348187A - Ultrasonic measuring apparatus - Google Patents

Abstract

PURPOSE:To enable the removal of an approximate noise wave by a method wherein reflected wave is received to be amplified to a detectable size, compared with a reference voltage to compute a waveform area at a part exceeding a reference level so that a maximum waveform part is detected as normal reflected wave. CONSTITUTION:Reflected wave from an object 14 to be measured is amplified to a detectable size by an amplifier 16 and outputted as amplification output V01. The output V01 is outputted to a computation circuit 10 while being outputted to a comparator 18 to be compared with a voltage of a reference level from a reference voltage source. Then, an area of a waveform at a part exceeding the reference level is computed with the circuit 10 to detect a waveform part having the maximum area as normal reflected wave. Time to the reception from the transmission of the reflected wave is computed and a distance data is converted to a distance signal by an output circuit 19 to be outputted to an output terminal 20. This enables the removal of a noise wave approximating the normal reflected wave.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention emits burst waves from an ultrasonic oscillation circuit to an object to be measured via an ultrasonic transducer using a tri-force pulse applied at a predetermined period. However, this ultrasonic measuring device receives the reflected wave reflected by the measurement object and measures the distance to the measurement object from the time difference between sending the trigger pulse and receiving the reflected wave. The present invention relates to an improved ultrasonic measuring device that can effectively distinguish between normal reflected waves and regular reflected waves.

<Prior art> As this type of ultrasonic measuring device, Japanese Patent Application Laid-Open No. 57-1003
62 (Japanese Patent Application No. 55-177553) is disclosed.

This technology uses a comparator to compare the output level of an amplifier that amplifies the received ultrasound signal with a reference level, and measures the time when the output level of the amplifier becomes higher than the reference level based on the output of this comparator. Based on this measurement result, a regular ultrasound signal to be received is detected.

<Problems to be Solved by the Invention> However, such an ultrasonic measuring device has the following problems. This will be explained with reference to the waveform diagram shown in FIG.

In Figure 6, the horizontal axis is time t, and the II axis is the amplified output of the amplifier.
. 1 is shown.

Vth is a reference level, and the waveform portion that exceeds this level is a normal reflected wave A, spike noise B,
, B2, and noise C, etc.9 The time width during which reflected wave A cuts below the reference level is ta, spike noise B+, B*
and the time width of noise C are tbl, tb2, respectively.
It is tc. And these waveforms are ta” (tb
+, tb 2 ), and tc~ta.

In this way, when the time widths tb1 and tb2 of the spike noises B, , B, are extremely small with respect to the time width ta of the regular reflected wave A, it is possible to remove these spike-like pulse noises, but the standard There is a problem in that a noise wave having a waveform similar to that of the normal reflected wave A, such as noise C, whose time is greater than the level Vth cannot be removed.

Means for Solving the Problems> In order to solve the above problems, the present invention aims to transmit signals to a measurement target from an ultrasonic oscillation circuit via an ultrasonic transducer using a trigger pulse applied at a predetermined period. In an ultrasonic measuring device that emits a burst wave at a target object, receives the reflected wave reflected by the object to be measured, and measures the distance to the object from the time difference between sending the trigger pulse and receiving the reflected wave, the reflection an amplifying means for amplifying the wave to a predetermined size; and a comparing means for comparing the output voltage of the amplifying means with a reference voltage having a preset reference level and outputting a comparison signal when the output voltage exceeds the reference level. , area calculating means for calculating the area of the waveform of the output voltage in the portion exceeding the reference level using this comparison signal, and calculating the area of the waveform of the output voltage with the maximum area to the normal reflection to the object to be measured. It is designed to be detected as a wave.

Function: The amplification means amplifies the reflected wave from the object to be measured to a predetermined size, the comparison means compares the amplified output voltage with a reference voltage having a preset reference level, and this reference level is determined. The area of the waveform of the output voltage exceeding the area is calculated by the area calculation means, and the waveform part of the output voltage with the maximum area is detected as a normal reflected wave to the object to be measured.

<Examples> Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention.

10 is an arithmetic circuit, from which a trigger pulse TP is outputted to the ultrasonic oscillation circuit 11 at a predetermined period. The ultrasonic oscillation circuit 11 applies a burst wave Vb to the ultrasonic transducer 13 via the switching circuit 12 in synchronization with the trigger pulse TP, thereby driving the ultrasonic transducer 13.

The ultrasonic pulse emitted from the ultrasonic transducer 13 is reflected by the measurement target 14 such as the liquid surface, is received by the ultrasonic transducer 13 again, and is sent to the amplifier 16 as a reception signal VR via the switching circuit 12. is input. The amplifier 16 amplifies this received signal vR to a detectable magnitude and outputs the amplified output VOI.
Output as .

The amplified output Vo1 of the amplifier 16 is output to the arithmetic circuit 10, and the other input of the comparator 18 is applied to one end of the input a reference voltage Er having a reference level Vth inputted from the reference power supply via the resistor 17. entered at the end.

The comparator 18 judges whether or not the amplified output o1 exceeds this reference level Vth, and sends the comparison output Vc to the arithmetic circuit 10.
Output to.

The arithmetic circuit 10 calculates the time from sending out the trigger pulse TP to receiving the amplified output vo1, which is considered to be a normal reflected wave, calculates the distance from the ultrasonic transducer 13 to the measurement target 14, and outputs the result. Output to circuit 19.

The output circuit 19 converts this distance data into a distance signal v1 corresponding to the set span and outputs it to the output terminal 2o.

Next, the operation of the embodiment configured as above will be explained with reference to the waveform diagram shown in FIG. 2.

Figure 2 shows the time t after sending out the ultrasonic pulse (t=o).
The amplified output V generated as the time progresses. , indicating a change in .

D, , D2, and D3 are 1, e.g. spike noise, E
, E2 indicates a pseudo reflected wave, and A indicates a normal reflected wave. A4 and A5 are branch elements included in the normal reflected wave A, respectively. These amplified outputs o, are judged by the comparator 18 as to whether or not they exceed the reference level Vth, and if they exceed Vth, the values of Vo+Erl are integrated, and the area of the waveform in the upper part Sdt, Se I, Sd2, Se
2, (Sa1 to 5a5), and Sds to the arithmetic circuit 1.
0, and the amplified output V0.0 has the largest area among these. (Reflected wave A in this case) is regarded as a regular reflected wave, and the time t1 until time Z when it crosses the reference level Vth is
The distance data is calculated as the distance between the ultrasonic transducer 13 and the measurement target 14 from
Output to 0.

FIG. 3 is a block diagram showing the configuration of a second embodiment of the present invention.

This embodiment differs from the embodiment shown in FIG. 1 in that an envelope detection circuit 21 is provided after the amplifier 16. Spike noise DI, D2, D3 of amplifier 16, pseudo reflected wave E
, ,E2. and the amplified output V consisting of the regular reflected wave A
o, is input to the envelope detection circuit 21, where the envelope of the waveform is detected and the spike noises D+ -, D2- are detected.
, D3°-1 pseudo reflected wave E+ -5E2-1 and normal reflected wave A- as shown in Figure 4, amplified output ■
Output o2.

Comparator 18 outputs this amplification ■. 2 and the reference voltage ET, it is determined whether or not the reference level Vth has been exceeded, and the comparison output VC- is outputted to the arithmetic circuit 10, and if the voltage exceeds Vtk as in the case shown in FIG. 1VO2Er
The area of the waveform portion exceeding Vth of each waveform is calculated by integrating the values of l. The result of this calculation is outputted to the output end 20 via the output circuit 19 as a distance signal Vj''.

However, the exact area Σ of each waveform of the amplified output vo2
Determining lVo+Erl and Σ1VO2By requires a complicated circuit configuration or a large memory capacity.

Therefore, an improved calculation in this respect will be explained using the waveform diagram shown in FIG.

The comparator 18 compares the amplified output Vo, (VO2) with the reference voltage Er, and based on the comparison output Vc (or Vc), the arithmetic circuit 10 determines the maximum value of the part exceeding this value, and generates a rectangular wave. Spike noise DRI approximated by
, DR2, DR), find the areas of the rectangular parts of the pseudo reflected waves ER1, DR2, and the regular reflected wave AR, and consider the waveform part with the largest area among these as the regular reflected wave,
An operation is performed to obtain the time t1 up to now.

If such a calculation is adopted, there is a high probability that the noise wave will be observed as a number of overlapping reflected waves, so Envelope 1 will expand and become close to a rectangle, and the detection area ratio of the normal reflected wave and the noise reflected wave will actually be The larger the size, the more reliable discrimination becomes possible.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, the reflected wave reflected from the measurement object is amplified to a predetermined magnitude by the amplification means, and the amplified output voltage and the preset A comparison means is used to compare the voltage with a reference voltage having a reference level of
The area of the output voltage waveform that exceeds this reference level is calculated by the area calculation means, and the part of the output voltage waveform with the largest area is detected as a normal reflected wave to the object to be measured. It is possible to simultaneously remove both electrical spike noise, which has a large reception amplitude, and acoustic noise, which may be observed for a long time but whose amplitude is smaller than the normal reflected wave.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention, FIG. 2 is a waveform diagram explaining the operation of the embodiment shown in FIG. 1, and FIG. 3 is a block diagram showing the configuration of another embodiment of the present invention. 4 is a waveform diagram explaining the operation of the embodiment shown in FIG. 3, and FIG. 5 is a waveform diagram explaining the operation when the calculation method is changed in the embodiment shown in FIG. 1 or 3. Waveform diagram FIG. 6 is a waveform diagram illustrating the problems of the conventional ultrasonic measuring device. 10... Arithmetic circuit, 11... Ultrasonic oscillation circuit, 12
...Switching circuit, 13...Ultrasonic transducer, 14...
・Measurement target, 18... Comparator, 19... Output circuit,
21...Envelope detection circuit.

Claims (1)

[Claims] A trigger pulse applied at a predetermined period causes a burst wave to be emitted from an ultrasonic oscillator circuit to an object to be measured via an ultrasonic transducer, and a reflected wave reflected by the object to be measured is received to generate a burst wave of the trigger pulse. An ultrasonic measuring device that measures the distance to the object to be measured based on the time difference between transmission and reception of the reflected wave, comprising: an amplifying means for amplifying the reflected wave to a predetermined size; and an output voltage of the amplifying means. Comparing means for comparing a reference voltage having a preset reference level and outputting a comparison signal when the reference voltage exceeds the reference level; and a waveform of the output voltage in a portion exceeding the reference level using the comparison signal. An ultrasonic measuring device comprising: area calculating means for calculating an area of the object, and detecting a waveform portion of the output voltage having the largest area as a normal reflected wave to the object to be measured.