JPS6033005A - Ultrasonic thickness gauge - Google Patents

Abstract

PURPOSE:To measure the thickness of a body to be measured accurately through simple operation by using angle information which is obtained by a reflected wave from the body and the difference in reception time between waves from the top surface and bottom surface of the body for arithmetic. CONSTITUTION:An ultrasonic wave having a predetermined amplitude is projected 5 upon the body 3 to be measured and a reflected wave from the body 3 is received 6. The amplitude of the receive wave is discriminated 8 on the basis of a predetermined threshold value and the angle of the ultrasonic wave to the body 3 is measured by the discrimination output when the receive wave amplitude exceeds the threshold value to store 10 the angle measurement output as the angle information. Further, the difference in the receive wave time between when a reflected wave from the top surface 3a of the body 3 is received and when a reflected wave from the bottom surface 3b is received is measured 11, and the thickness of the body 3 is calculated 15 on the basis of this measurement output and the stored angle information.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an ultrasonic technology that projects ultrasonic waves onto an object to be measured and measures the thickness of the object based on the reflected waves of the ultrasonic waves from the object. Regarding sonic thickness gauge.

<Prior art and its problems> In such an ultrasonic thickness gage, the reflected waves generally include a first reflected wave that is reflected from the surface of the object to be measured, and a first reflected wave that is not reflected from the surface of the object to be measured but inside the object. There is a second reflected wave that passes through the 1. The thickness of the object to be measured is measured based on the difference Δt between the times when the second reflected waves are received by the wave receiving means arranged at specific positions and the speed of sound C in the object to be measured. It has become. By the way, some conventional ultrasonic thickness gauges use the sound velocity in a test piece separate from the measured object as the sound speed C in the measured object. However, determining the sound velocity in advance using a test piece has the problem of complicating the operation of measuring the thickness of the object to be measured. In addition, the actual object to be measured and the test piece must have completely the same structure, and the conditions for measuring the speed of sound in the test piece must completely match the conditions for measuring the thickness of the object to be measured. Although it cannot be said that the speed of sound is accurately determined,
It is very difficult to accurately determine the speed of sound in this way.

Therefore, no matter how accurately the time difference Δt necessary for determining the thickness of the object to be measured can be obtained, it is difficult to accurately determine the speed of sound C in the object to be measured. As mentioned above, there are difficulties in accurately measuring the thickness.

<Objective of the Invention> An object of the present invention is to enable accurate measurement of the thickness of an object to be measured with simple operation.

<Configuration and Effects of the Invention> In order to achieve the above object, the present invention provides a means for projecting ultrasonic waves having a predetermined amplitude toward an object to be measured, and a means for projecting ultrasonic waves having a predetermined amplitude toward an object to be measured, and a means for projecting ultrasonic waves having a predetermined amplitude toward an object to be measured, and a means for receiving the waves;
means for discriminating the received wave amplitude of the wave receiving means using a predetermined threshold; and means for discriminating the received wave amplitude of the wave receiving means based on the output of the discriminating means when the received wave amplitude exceeds the threshold; means for measuring an angle with respect to the object to be measured; means for storing the output of the angle measuring means as angle information;
means for measuring the difference in reception time when a reflected wave from the surface of the object to be measured and a reflected wave from the bottom thereof are received by the wave receiving means, respectively; and means for calculating the thickness of the object to be measured based on the angle information stored in the storage means.

With this configuration, the present invention obtains information regarding the angles of incidence, reflection, and refraction of the ultrasonic wave on the object to be measured from the output of the discrimination means, and uses the calculation means to determine the angles of incidence, reflection, and refraction in the object to be measured based on the angle information. The speed of sound is calculated, and the thickness of the object to be measured is further calculated by the calculating means from this speed of sound and the difference between the times. Therefore, according to the present invention, in order to determine the speed of sound in the object to be measured,
f.

There is no need to first determine the sound velocity in the test piece, and the sound velocity in the object to be measured can be directly determined, which simplifies the measurement operation. Furthermore, since the speed of sound in the object to be measured can be determined using the object to be measured, the speed of sound can be determined accurately, and therefore the thickness of the object to be measured can be accurately measured.

<Description of Embodiment> The present invention will be described in detail below based on an embodiment shown in the drawings.

FIG. 1 is a circuit diagram of an ultrasonic thickness gauge according to this embodiment. In FIG. 1, reference numeral 1 denotes means for projecting an ultrasonic wave 2 having a predetermined amplitude onto an object to be measured 3. As shown in FIG.

The projection means 1 includes a pulser 4 and an ultrasonic transmitter 5 that transmits ultrasonic waves having a certain high frequency in the form of a beam. 6
8 is an ultrasonic receiver as a means for receiving the reflected wave 7 from the object to be measured 3, and 8 is the received wave amplitude of the ultrasonic receiver 6, taking into consideration detection efficiency and attenuation of the ultrasonic wave in the propagation path. A power detector 9 serves as a means for discriminating based on a predetermined threshold value, and a power detector 9 detects the reflected wave 7 by the output of the power detector 8 when the received fIIi amplitude of the reflected wave 7 exceeds the 1° threshold value. This is an angle measuring device as a means for measuring the reflection angle of the wave 7 with respect to the object to be measured 3.Here, the ultrasonic transmitter 5 and the ultrasonic receiver 6 are composed of, for example, an ultrasonic transducer. They always face at the same angles θi and θr (-θi) with respect to the normal n made on the surface 3a of the object to be measured 3.The ultrasonic wave 2 incident on the object to be measured 3 The reflected wave 7 reflected on the surface 3a of is the first reflected wave, and the bottom 1117 of
The reflected wave 7' reflected by 3b is the second reflected wave, and the second reflected wave is
The refraction angle of the reflected wave 7' is assumed to be θt. In addition, the object to be measured 3
Let the sound speed outside be C and the sound speed inside the object to be measured 3 be 02. Then, the following formula +11[2+ holds true for each of the above.

sin OL =: sinθr = 0) sinθt
/s 1nθ' = "z/"s... (21 Therefore, when sinθt-1, that is, θj, = 9QO, and the ultrasonic wave 2 is totally reflected on the surface 3a of the object to be measured 3, the object to be measured 3 The sound speed C2 in the equation (3) is given by the following equation (3).

C2=C,/sinθr”!3) In this equation (3), C1 is assumed to be the value of the medium in which the ultrasonic wave propagates, such as water or oil, whose value is determined accurately. The speed of sound can be determined by setting the angle θr. Therefore, the angle at which the ultrasonic transmitter 5 and the ultrasonic receiver 6 face each other is, for example, θi-t・, θr
-1i 7) When the received wave amplitude P1 of the power detector 8 is smaller than the threshold value, the ultrasonic transmitter 5 and the ultrasonic receiver 6
Increase the angle at which they face each other by a small angle Δθ, and the angle at which they face each other becomes θi−θi−1 1,000Δθ, θr=θr−1
+Δθ. Such facing angle θ1. The received wave amplitude Pi of the power detector 8 when θr exceeds the threshold value. Next, when the received wave amplitude becomes larger than the threshold value, and even if the small angle Δθ is further increased, the received wave amplitude Pi does not increase any more, and when it matches the previous received wave amplitude Pi, the ultrasonic The ultrasonic waves 2 from the transmitter 5 strike the surface 3 of the object to be measured 3.
It shows that there is total internal reflection at point a. The angle θr in the equation (3) is measured based on the discrimination output of the power detector 8 at this time. Note that the power detector 8 is a detector that uses magnetostriction or electrostriction phenomena, and if it can be angularly displaced together with the ultrasonic receiver 6, the normal n of the object to be measured 3 of the ultrasonic receiver 6 An output corresponding to the angle θr relative to the angle θr can be given to the angle measuring device 9. Reference numeral 10 denotes a program/data memory as means for storing the output of the angle measuring device 9 as angle information.

Reference numeral 11 denotes a first waveform of the ultrasonic wave 2 projected from the projection means 1 to the object to be measured 3. This is a means for measuring the difference Δt between the times at which the second reflected waves 7 and 7' are received by the ultrasonic receiver 6. This measuring means 11 is a gate circuit in which the gate is opened by the first detection output corresponding to the first reflected wave 7 from the power detector 8, and the gate is closed by the second detection output corresponding to the second reflected wave 7'. 12, clock oscillator 13, and gate circuit 1
The counter 14 counts the clock from the clock oscillator 13 only while the gate output from the clock oscillator 2 is being applied. 15 is a CPU that controls the overall operation and also has the function of 1 calculation means;
5 is given angle information from the angle measuring device 9 via the first A/D converter 16. The CPU 15 stores this angle information in the program/data memory 10. In addition to angle information, the program/data memory 10 also contains information about the CPU 1.
It also stores a program that defines the operation of step 5.

Further, the output of the measuring means 11 is given to the CPU 15 via the second A/D converter 17. The CPU 15 calculates the thickness of the object to be measured 3 based on the output of the opening side means 11 and the angle information stored in the program/data memory 10.

18 is a thickness display unit that displays the thickness of the object to be measured 3 which is the output of cpulH, and 19 is an interface.

Next, the operation will be described with reference to the time chart in FIG. 2 and the flowchart for measuring the speed of sound in FIG. 3. FIG. 2(a) shows the pulse waveform of the mackerel sound wave 2 from the ultrasonic transmitter 5, and FIG. 2(b) shows the pulse waveform of the 1° second reflected wave 7, 7.
' indicates the first and second outputs of the power detector 8 corresponding to
Figure 2 (C) is the first. A gate pulse output from the gate circuit 12 is shown by the second output. FIG. 2(d) shows the clock pulse from the clock oscillator 13, and FIG.
e) shows a clock pulse from the clock oscillator 13 that can be input to the counter 14 for counting. First, in step n1, the output Pi of the power detector 8 is normalized in order to measure the speed of sound in the object to be measured 3. Ultrasonic waves 2 shown in FIG. 2(a) are projected from an ultrasonic transmitter 5 onto an object 3 to be measured. When the incident angle θi of the ultrasonic wave 2 with respect to the object to be measured 3 is small, the ultrasonic wave 2 is not only reflected by the surface 3a of the object to be measured 3, but also is refracted and enters the object to be measured 3. Once, the output P1 of the power detector 8 was the ultrasonic wave 2
is smaller than a predetermined threshold value FT)I when total reflection occurs on the surface 3a of the object to be measured 30. Therefore, in step n2, it is determined that Pi) is not PTH, and step n2 is performed.

Proceed to. Next, the mutual facing angle of the ultrasonic transmitter 5 and the ultrasonic receiver 6 is 01. The output P1→ of the power detector 8 after increasing θr by Δθ is measured in step n3. In this way, the output P1 of the power detector 8 becomes Pi)P
When it becomes ro, it is determined as Y]IcS in step n2, and in the next step n4, it is determined whether the output Pi matches the previous output Pi of the power detector 8.

If it is determined that they do not match because the ultrasonic wave 2 has not yet been totally reflected on the surface 3a of the object to be measured 30, the process proceeds to step n5. In step n5, the same processing as in step - is performed. In this way, when the angles θi and θr are reached until the ultrasonic wave 2 is totally reflected on the surface 3a of the object to be measured 30, the output P1 matches the previous output Pi, so it is determined YES in step n4. The CPU 5 stores the output of the angle measuring device 9 at this time in the program/data memory 10 as angle information θC in step n. Next, in the step book, the CPU 15 calculates the speed of sound C2 in the object to be measured 3 by calculating the equation (3) based on this angle information θC. In this way, the speed of sound C2
measurement is completed.

Next, calculate the difference Δt between the reception times of the reflected waves 7 and 7'.

First, the measuring means 11 detects the first output of the power detector 8 corresponding to the first reflected wave 7 on the surface 3a of the reflected waves of the ultrasonic wave 2 on the object 3 to be measured, and the first output on the bottom surface 3b thereof. The second output of the power detector 8 corresponding to the second reflected wave 7' of
As shown in FIG. 2(C), a gate pulse is output from the gate circuit 12 between times t1 and t2. The counter 14 counts the clock of the clock oscillator 13 shown in FIG. 2<e) by the gate pulse from the gate circuit 12. This count output is sent to the CP via the A/D converter 17.
Given to U15. The CPU 15 calculates the difference Δt between the reception times of the first reflected wave 7 and the second reflected wave 7' based on the A/D converted count output. In this way, C
The PU 15 calculates the thickness d of the object to be measured 3 as follows based on the sound velocity c2 in the object to be measured and the difference Δt between the reception times.
Calculate.

First, if the clock frequency is f megahertz, the clock pulse interval is 1. is (1/f)x l O' seconds. When the number of clock pulses counted by the counter 14 is n during the period 'ra (2 Δt) shown in FIG. 2, the difference Δt in the reception time is given by n×10′/f seconds. Therefore, the thickness d of the object to be measured 3 is calculated by the following formula (
4) is given by

d=(nX10/f)XC2X100-[4] Here, as a specific example, f230 MHz, n=509
2 = 5900 me) le/s are given respectively,
Further, when given as the calculation result, the CPU 18 performs calculation based on this numerical value according to the above equation (4), and displays the thickness d as approximately 5'0.0 knee 17 meters on the thickness display section 18.

[Brief explanation of the drawing]

The drawings relate to an embodiment of the present invention; FIG. 1 is an overall circuit diagram, and FIG. 2 is a measuring means 1 for measuring the difference in reception time of each reflected wave.
FIG. 3 is a timing chart for explaining the operation of step 1, and FIG. 3 is a program flowchart for determining the speed of sound in the object to be measured 3. 1. Projection means, 2. Ultrasonic waves, 3. Object to be measured, 3
a...Surface, 3b...Bottom, 5...Ultrasonic transmitter, 6...
・Ultrasonic receiver, 7.. First reflected wave, 7'.. Second reflected wave, 8.. Power detector, 9.. Angle measuring device, 10..
Program/data memory, 11...Measuring means, 15.
・CPU. Figure 2 Figure 3

Claims (1)

[Claims] (1) A means for projecting an ultrasonic wave having a predetermined amplitude toward an object to be measured, a means for receiving a reflected wave from the object to be measured, and a receiving amplitude of the receiving means, means for discriminating based on a predetermined threshold; and the received wave amplitude is
means for measuring the angle of the ultrasonic wave with respect to the object to be measured based on the output of the discriminating means when the threshold value is exceeded;
means for storing the output of the angle measuring means as angle information; and of the reflected waves of the ultrasonic waves projected from the projection means on the object to be measured, the waves reflected from the surface of the object to be measured and the waves reflected from the bottom surface thereof; means for measuring the difference in reception time when each wave is received by the wave receiving means; An ultrasonic thickness gauge comprising means for calculating thickness.