JP2803192B2 - Ultrasonic measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention radiates a burst wave from a ultrasonic oscillation circuit to an object to be measured via an ultrasonic transducer by a trigger pulse applied at a predetermined cycle. The present invention relates to an ultrasonic measurement device that receives a reflected wave reflected by an object to be measured, and measures a distance to the object to be measured from a time difference between the transmission of a trigger pulse and the reception of the reflected wave. The present invention relates to an improved ultrasonic measuring device capable of effectively distinguishing a regular reflected wave.

<Prior Art> Japanese Patent Application Laid-Open No. 57-100362 discloses this type of ultrasonic measuring apparatus.
(Japanese Patent Application No. 55-177553).

This technique compares the output level of an amplifier that amplifies a received ultrasonic signal with a reference level and a comparator, and measures a time when the output level of the amplifier becomes larger than the reference level based on the output of the comparator. A normal ultrasonic signal to be received is detected based on the measurement result.

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

FIG. 6 shows the time t on the horizontal axis and the amplified output V _{o1 of the} amplifier on the vertical axis.
Is shown.

V _th is a reference level, and the waveform portion exceeding this is a regular reflected wave A, a spike noise B ₁ ,
B ₂ and noise C. The time width during which the reflected wave A crosses the reference level is t _a , and the time widths of the spike noises B ₁ , B ₂ and noise C are t _b1 , t _b2 , and t _c , respectively. These waveforms have _a relationship of t _a ≪ (t _b1 , t _b2 ) and t _c t _a .

When spike noise B _1, B ₂ of the time width t _b1, t _b2 is extremely small for the time width t _a of the thus normalized reflected waves A, removal is possible spike pulse noise such as this However, there is a problem that a noise wave whose time when it becomes larger than the reference level _Vth approximates the normal reflected wave A, for example, a waveform having a waveform such as noise C cannot be removed.

<Means for Solving the Problems> In order to solve the problems as described above, the present invention provides a method for measuring an object to be measured from an ultrasonic oscillation circuit via an ultrasonic transducer using a trigger pulse applied at a predetermined cycle. In an ultrasonic measurement device that radiates a burst wave and receives a reflected wave reflected by the measurement object and measures a distance to the measurement object from a time difference from transmission of a trigger pulse to reception of the reflected wave, Amplifying means for amplifying a wave to a predetermined magnitude; comparing means for comparing an output voltage of the amplifying means with a reference voltage having a preset reference level, and outputting a comparison signal when the reference level is exceeded. Using this comparison signal, the waveform of the output voltage at the portion exceeding the reference level is approximated by a rectangular wave, the area of the rectangular wave is calculated, and the waveform portion of the output voltage having the largest rectangular wave is measured. Stuff And an area calculating means for calculating a distance from the ultrasonic transducer to the object to be measured by detecting the reflected wave as a regular reflected wave.

<Operation> The amplifying means amplifies the reflected wave reflected from the object to be measured to a predetermined magnitude, compares the amplified output voltage with a reference voltage having a preset reference level, and compares the reference level with this reference level. The area of the output voltage waveform at the portion exceeding the area is calculated by the area calculating means, and the waveform portion of the output voltage having the maximum area is detected as a regular reflected wave to the object to be measured.

<Example> Hereinafter, an example of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention.

An arithmetic circuit 10 outputs a trigger pulse _TP to the ultrasonic oscillation circuit 11 at a predetermined cycle. Ultrasonic oscillation circuit 11 is a burst wave V _b is applied through the switching circuit 12 in synchronism with the trigger pulse T _P to the ultrasonic transducer 13 to drive the ultrasonic transducer 13.

The ultrasonic pulse radiated from the ultrasonic transducer 13 is reflected by the measurement target 14 such as a liquid surface, and is again returned to the ultrasonic transducer 13.
Is received, it is input to the amplifier 16 as a reception signal V _R through the switching circuit 12. In the amplifier 16 is output as an amplified output V ₀₁ amplifies the received signal V _R to a detectable size.

The amplified output _Vo1 of the amplifier 16 is output to the arithmetic circuit 10 and the comparator 18 to which a reference voltage _Er having a reference level _Vth input from a reference power supply via a resistor 17 is applied to one end of the input. It is input to the other input terminal.

Comparator 18 amplifies the output V _o1 outputs a comparison output V _C to the decision whether or not exceeded the reference level V _th to the arithmetic circuit 10.

Calculation circuit 10 calculates the time until receiving the amplified output V _o1 seen the regular reflected waves from the delivery of the trigger pulse T _P, now calculates the distance from the ultrasonic transducer 13 to the measurement target 14 , To the output circuit 19.

The output circuit 19 outputs to the output terminal 20 in terms of the distance signal V _l corresponding to the distance data in the set span.

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

FIG. 2 shows a change in the amplified output _Vo1 generated as time t elapses after the transmission of the ultrasonic pulse (t = 0).

D ₁ , D ₂ , and D ₃ are, for example, spike noise, E ₁ , E ₂
Represents a pseudo reflected wave, and A represents a regular reflected wave. A ₁ , ~
A ₅ represents a respective wave element respectively contained in the regular reflected wave A.
Amplified output V _o1, such this will be determined whether exceeds the reference level V _th at the comparator 18, if it exceeds the V _th | V _o1 -E _r | by accumulating the values, the upper part of this Waveform area S _d1 , S _e1 , S
_d2 , S _e2 , (S _{a1 to} S _a5 ), and S _d3 are each calculated by the arithmetic circuit 10, and the amplified output V ₀₁ having the largest area among them is calculated.
(Reflected wave A in this case) is regarded as a regular reflected wave, and is calculated as the distance between the ultrasonic transducer 13 and the measuring object 14 from the time t ₁ up to the time Z intersecting the reference level V _th, and this distance is calculated. data in terms of the distance signal V _l corresponding to the set span in the output circuit 19 is output to the output terminal 20.

FIG. 3 is a block diagram showing the configuration of the 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 at a stage subsequent to the amplifier 16. Amplifier 16
Spike noise _{D 1, D 2, D 3} , pseudo reflected wave E _1, E _2, and an amplified output V _o1 consisting reflected waves A regular input to the envelope detection circuit 21 detects the envelope here waveform And spike noises D ₁ ′, D ₂ ′, D ₃ ′, pseudo reflected waves E ₁ ′, E ₂ ′,
Then, an amplified output _Vo2 is output as a regular reflected wave A 'in the form shown in FIG.

Comparator 18 whether exceeds the reference level V _th by comparing the amplified output V _o2 and the reference voltage E _r is determined, in FIG. 1 and outputs the comparison output V _C 'to the arithmetic circuit 10 As in the case shown, when V _th exceeds V _th , the value of | V _o2 −E _r | is integrated to calculate the area of the waveform portion _exceeding V _th of each waveform. This calculation result is output to the output terminal 20 via the output circuit 19 as a distance signal V _l '.

However, the exact area of each waveform of the amplified output V _o2 Σ |
To obtain V _o1 −E _r | and Σ | V _o2 −E _r | requires a complicated circuit configuration or a large memory capacity.

Therefore, an improved calculation of this point will be described with reference to the waveform diagram shown in FIG.

The amplified output V _o1 (or V _o2 ) is compared with the reference voltage _Er by the comparator 18 and based on the comparison output V _C (or V _C ′), the arithmetic circuit 10
The maximum value of the portion exceeding this value is obtained, and the spike noises D _R1 , D _R2 , D _R3 , the pseudo reflection waves E _R1 , E _R2 , and the square part of the regular reflection wave A _R approximated by a square wave, respectively. An area is obtained, and a waveform portion having the largest area among them is regarded as a normal reflected wave, and an operation for _obtaining the time tl up to this is executed.

When such a calculation is adopted, the noise wave is likely to be observed as a superposition of several reflected waves, so the envelope expands and becomes close to a rectangle, and the detection area ratio between the regular reflected wave and the noise reflected wave is larger than the actual area. It becomes larger and reliable determination becomes possible.

<Effects of the Invention> As described above in detail with the embodiments, according to the present invention, the reflected wave reflected from the object to be measured is amplified to a predetermined magnitude by the amplifying means, and the amplified output voltage is set in advance. The comparison means compares the reference voltage having the reference level obtained by the comparison means, calculates the area of the output voltage waveform exceeding the reference level by the area calculation means, and measures the waveform portion of the output voltage having the largest area to be measured. Since it is detected as a normal reflected wave to the object, both the received amplitude is large but the electrical spike noise, and the acoustic noise that is likely to be observed for a long duration is smaller than the reflected wave. can do.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention, FIG. 2 is a waveform diagram illustrating the operation of the embodiment shown in FIG. 1, and FIG. 3 is the configuration of another embodiment of the present invention. 4 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 3, and FIG. 5 is a diagram for explaining the operation when the operation method is changed in the embodiment shown in FIG. 1 or FIG. FIG. 6 is a waveform diagram for explaining a problem of the conventional ultrasonic measuring device. 10 arithmetic circuit, 11 ultrasonic oscillation circuit, 12 switching circuit, 13 ultrasonic transducer, 14 measuring object, 18 comparator, 19 output circuit, 21 Envelope detection circuit.

Claims (1)

(57) [Claims] 1. An ultrasonic oscillation circuit emits a burst wave to an object to be measured via an ultrasonic transducer by a trigger pulse applied at a predetermined cycle, and receives a reflected wave reflected by the object to be measured. An ultrasonic measuring apparatus for measuring a distance to the object from a time difference between the transmission of the trigger pulse and the reception of the reflected wave, wherein amplifying means for amplifying the reflected wave to a predetermined size; Comparing means for comparing the output voltage of the means with a reference voltage having a preset reference level and outputting a comparison signal when the reference level is exceeded; and The waveform of the output voltage is approximated by a rectangular wave, the area of the rectangular wave is calculated, and the waveform portion of the output voltage having the maximum area of the rectangular wave is detected as a regular reflected wave to the object to be measured. Ultrasonic measuring apparatus is characterized by comprising the area calculation means for calculating the distance from the ultrasonic transducer to the measurement object.