JPS6367512A - Reflected wave processing method for ultrasonic wall thickness meter - Google Patents

Abstract

PURPOSE:To eliminate the preset time required for correcting a phase inversion error in the reception of ultrasonic waves reflected at the rear surface by inverting the current polarity of the reception part when either one of alternate waves reflected at the front- and rear surfaces is expected to be received. CONSTITUTION:An ultrasonic signal source 6, of which the output timing is controlled by a timing circuit 7, emits T waves for every prescribed time via a transmitter-receiver 4. The S wave and B wave reflected by a pipe 8 are impressed on a comparator 9 via an amplifier 8. An analog switch 19 impresses the output of a first output terminal 13 on the comparator 9 until the prescribed time t1 elapses after the comparator 9 detects the incoming of the S wave and impresses the output of a terminal 14 on the comparator 9 after the time t1 elapses.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an ultrasonic wall thickness meter that measures the wall thickness of an object to be measured using ultrasonic waves.

Conventional technology Ultrasonic wall thickness gauges are used in two ways: contact type, in which the transducer is pressed against the object to be measured; It can be classified as a water immersion type, in which the llq constant is submerged in a water tank and ultrasonic waves are transmitted and received through the water in the tank.

Since the operating principle is the same in both the contact type and the water immersion type, the water immersion type will be explained here as an example.

Figure 5 shows the usage of the water immersion type, in which a pipe 1 as an object to be measured is submerged in a water tank 2, and a transducer 4 with a transmitting/receiving port inserted under the water surface 3 emits ultrasonic waves toward the pipe 1. death〔
A surface reflected wave reflected from the surface of pipe 1 [hereinafter referred to as B wave], and a back surface reflected wave reflected from the back surface of pipe 1 [hereinafter referred to as B wave]. The wave is received by the transducer 4, and the thickness d of the pipe 1 is calculated based on the time difference between the B wave and the arrival time of the B wave to the transducer 4.

FIG. 6 shows the transmission and reception times of the T wave, B wave, and B wave and their waveform diagrams. The wall thickness d is calculated based on the time difference between the reception of the B wave and the B wave and the transmission speed of the ultrasonic wave inside the pipe 1. However, as you can see by comparing the B wave and the B wave, the phase of the B wave is shifted by π, so it is necessary to compare the received reflected waves using the judgment level v1 as a reference, or to judge the peak and distinguish between the B wave and the B wave. When it is determined that the B wave has arrived, the detection time of the B wave is delayed by a certain amount of time. Conventionally, the time τ is preset, and the wall thickness d is calculated by correcting the time difference using this preset time.

Problems to be Solved by the Invention In such a conventional configuration, it is necessary to preset the time τ, and the time τ changes depending on the ultrasonic frequency. Therefore, if the setting of time τ is not changed when the ultrasonic frequency changes from 3.0 (Ml(Z) to 5.0 [MIIz), the propagation velocity inside the pipe 1 will change to 3.0 [MIIz].
000 (s/sl), an error of 0.2 (m) will occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a reflected wave processing method that does not require a presetting operation of the time τ and can obtain accurate wall thickness without adjustment even when the ultrasonic frequency changes.

Means for Solving the Problems The reflected wave processing method in the ultrasonic wall thickness gauge of the present invention is based on the time difference between the front reflected wave and the back reflected wave that are reflected from the front and back surfaces of the object to be measured and arrive at the receiving section. When calculating the wall thickness of the object to be measured based on It is characterized by inverting the polarity of the signal and detecting the arrival of each reflected wave from the output signal of the receiving section from time to time.

Effect: According to this configuration, the output signal of the receiver has the same phase when receiving the front reflected wave and when receiving the back reflected wave, so there is no need to preset the time τ as in the conventional case.

EXAMPLES Hereinafter, the reflected wave processing method of the present invention will be explained based on specific examples.

FIG. 1 shows an ultrasonic wall thickness meter employing the reflected wave processing method of the present invention, in which the drawing controller 5 is operated based on the calculated wall thickness to increase the drawing speed of the pipe 1 during pultrusion forming. is used to control.

In the ultrasonic signal source 6, the output timing of the ultrasonic signal is controlled by a timing circuit 7, and the output timing of the ultrasonic signal is controlled by a timing circuit 7.
), it emits T waves at regular intervals. The B wave and the B wave reflected from the pipe 1 with a time difference as shown in FIG. 2(b) are applied to a comparator 9 via an amplifier 8. The comparator 9 compares the reference level v1 with the output signal v0 of the amplifier 8 as the output signal of the receiving section, and every time it detects ■1≦■o, the output level increases to the fifth level.
It changes as shown in figure (d).

The integrator 10 receives the signal from the timing circuit 7 [Fig.
)] at a constant time of 1tll from the T-wave emission time.
t, the integration of the reference voltage 7 is started later, and when the comparator 9 detects the arrival of the B wave, the wall thickness calculation unit 11
takes in the output value of the A/D converter 12 which digitally converts the integral value of the integrator 10 at that time as the first sample hold value 5H1 (see FIG. 2(g)).

The amplifier 8 is constituted by an operational amplifier OP of the equivalent circuit shown in FIG. This operational amplifier oP has a first output terminal 13 and a second output terminal 14, and if the gain is A and the input signal level is El, then between the first output terminal 13 and the ground 15 ( A/EI) signal is generated,
At the same time, a -(A-EI) signal is generated between the second output terminal 14 and the ground 15. 16 is an input impedance, and 17.18 is an output impedance.

The analog switch 19 provided at the output of the amplifier 8 is
The comparator 9 detects the arrival of the B wave and waits for a certain period of time t.
1 elapses, the first output terminal 13 (A-EI
) is applied to the input of the comparator 9, and after the above-mentioned fixed time t1 has elapsed, the signal of the timing circuit 7 [Fig. 2 (
e)] and the - of the second output terminal 14 is switched.
(A-EI) is applied to the input of comparator 9.

Since the analog switch 19 is switched in this way, the B wave is applied to the input of the comparator 9 as a waveform with the polarity reversed from that in FIG. 2(b), as shown in FIG. 2(c). Therefore, the arrival of the B wave can be detected without a phase difference of π unlike the conventional method.

When the comparator 9 detects the arrival of the B wave, the wall thickness calculation unit 11 takes in the output value of the A/D converter 12 at that time as the second sample hold value SH, and (SHl-5
R2) is the data corresponding to the time difference t between the B wave and the B wave, and the wall thickness of the pipe 1 (
d) is calculated and outputted to the wall thickness display section 20 and the drawing control section 5 as an actual measurement value.

In the above embodiment, the analog switch 19 is switched at a certain time t1 after the detection of the arrival of the B wave.

This time t can be set to any time before the start of the expected reception period of the B wave.

In the above embodiment, during the expected reception period of the B wave, the polarity of the output signal of the amplifier 8 applied to the comparator 9 is -(A-Et
), but this is -(A-E) during the expected reception period of B wave.
t) and (A-Et) during the expected reception period of the B wave.

In the above embodiment, the output signal of the receiving section is compared at the reference level v0, but it is also possible to detect the arrival of the B wave and the B wave even if the inflection point of the output signal of the receiving section is detected.

In FIG. 3, the wall thickness was measured only at one location in the circumferential direction of the pipe 1, but as shown in FIG. The transducers 48 to 4d are connected to the ultrasonic signal source 6 and the amplifier 8 via the scan circuit 21, and the scan circuit 21, which is controlled by the control signal 22, selects one of the transducers 4a to 4d to be used. By configuring it to select sequentially in time division,
Can measure wall thickness at multiple locations.

As described in detail, in the present invention, the expected reception period of one of the front reflected wave and the back reflected wave is different from the expected reception period of the other reflected wave. Reverse 1
Since the arrival of each reflected wave is detected from the output signal of the receiving section from time to time, the phase of the front reflected wave and the back reflected wave are aligned in the output signal of the receiving section. It does not require a preset time for correction, and can accurately measure wall thickness without adjustment even if the ultrasonic frequency changes.

[Brief explanation of drawings]

1 to 3 show a specific embodiment of the present invention, FIG. 1 is a configuration diagram of the main parts of a pultruded pipe manufacturing apparatus, FIG. 2 is a waveform diagram of the main parts of FIG. 1, and FIG. 3 is an equivalent circuit diagram of the amplifier in FIG. 1, FIG. 4 is a main part configuration diagram of another embodiment,
FIG. 5 is an explanatory diagram of the operating principle of the ultrasonic wall thickness meter, and FIG. 6 is a waveform diagram of transmitted and received waves illustrating a conventional reflected wave processing method. 1... Pipe [object to be measured], 4... Transducer/receiver, 6...
... Ultrasonic signal source, 7... Timing circuit, 8...
Amplifier, 9... Comparator, 11... Thickness calculation unit, 13.14... First of the amplifier. second output terminal, 1
9...Analog switch, S...Surface reflected wave, B...
...Back surface reflected wave, V, ...Amplifier output signal [receiver output signal]. Agent Yoshihiro Morimoto Figure 2 Figure S Figure

Claims (1)

[Claims] 1. When calculating the wall thickness of the object to be measured based on the time difference between the front reflected wave and the back reflected wave that are reflected from the front and back surfaces of the object and arrive at the receiver, The expected reception period of one of the reflected waves is different from the expected reception period of the other reflected wave.The polarity of the output signal of the receiving section is inverted, and the arrival of each reflected wave is determined from the output signal of the receiving section from time to time. A method for processing reflected waves in an ultrasonic wall thickness meter that detects