RU1535139C - Ultrasonic method of determining thicknese of film articles - Google Patents

Abstract

The invention makes it possible to measure the thickness of film materials with high accuracy. The aim of the invention is to improve the accuracy of measurement. Create a reference and measuring electro-acoustic channels. A controlled product is introduced between the emitter and the receiver of the measuring channel, the acoustic vibrations passed through the controlled product are received, and the ratio of the amplitudes of the received and radiated acoustic vibrations is determined. The phase difference of the oscillations of the reference and measuring channels is also measured. The thickness of the controlled product is determined from the expression h (arctgijl-w2 / W) - Л If c / 2 "T, where W is the ratio of the amplitudes of the transmitted product and the emitted oscillations; & q is the phase difference of the oscillations of the reference and measuring canlop caused by the introduction of a controlled product; c is the speed of propagation of acoustic vibrations in air; f is the frequency of acoustic vibrations. In order to increase the amplitude of the acoustic vibrations transmitted through the controlled article, their frequency is selected from the ratio f 0.01 (c0 / h max), where c0 is the propagation velocity of acoustic vibrations in the material of the controlled product; h max the maximum possible thickness of the controlled product. 1 s.p. f-ly, 1 ill. o (L ate ate

Description

The invention relates to measuring technique and can be used for non-contact measurement and control of the thickness of film materials.

The aim of the invention is to increase the accuracy of measuring the thickness of film materials by eliminating the influence of the physicomechanical characteristics of the material of the product on the measurement result, as well as eliminating the diffraction distortion of acoustic vibrations.

The drawing shows a structural diagram of a device that implements the proposed method.

The device comprises a stable frequency generator 1, a power amplifier 2, radiating 3 and receiving electro-acoustic transducers of the measuring channel, radiating 5 and receiving 6 electro-acoustic transducers of the reference channel, amplifier 7 with automatic gain control (AGC), phase Converter 8, adjustable phase shifter 9,

3 1535

an adjustable attenuator 10, a ratio block 11, an analog-to-digital converter (ADC) 12, micro-EVI 13, an ADC And a digital indicator 15.

The proposed method is as follows.

A monitored article 16 is inserted between the emitter and the receiver of the electro-acoustic measurement channel. In this case, the phase difference between the measuring and reference (similar to the measuring, in whose acoustic channel there is only air) electro-acoustic channels does not depend on the parameters of the air medium (temperature, humidity) and can be represented as

Alf - kh-farctg | (+ |) tgk0h, (1)

, 2CHGЈ. 27f. where k "; kBe - f coefficients;

 c0 c is the velocity of propagation of acoustic vibrations t in the material of the controlled product and in the medium, respectively;

 p - the density of the material of the controlled product and environment, respectively;

- the ratio of the acoustic impedance of the controlled product and the medium, respectively; h is the thickness of the controlled product; , Ј - acoustics frequency

fluctuations

Since the environment is air, which has a significantly lower acoustic resistance than the controlled material (grew - () s), we can assume. Then

DC -kh + arctgj ftglc0hi (2)

The amplitude of the acoustically received vibrations that have passed the air gaps and the product being monitored can be represented as

Ry9a RS

H

1IChL

4cos8k hVi $ sin k h

Determine the ratio of the amplitudes of the received and emitted acoustic vibrations 1

TO

H

(AND)

cos2k0h + r 2 sin

k0h

Since the amplitude of the acoustic vibrations that passed the controlled product is much smaller than the amplitude of the emitted acoustic vibrations, to increase it (increase the signal to noise ratio), taking into account that, choose

sin or

k.

f

G.

Usually choose k0hgO, 02-,

, t

c0

(5)

(6)

then

(7)

where does the frequency of acoustic vibrations

f Ј0.0lЈ.

(3)

When expressing (5), expressions (2) and (k) can be represented as

5

0

u “f -kh + arctg | fkeh,

f + | F (kIhp Expressing from the expression

Well, substituting it (9) we get

T - w UCf -kh + arctg ----,

where from

(arctg

- ulf) s

 Iw

(9) (10)

(10) in the expression

(11) (12)

35

.

x SS

45

From the expression (12) it follows that the thickness of the controlled product does not depend on the physicomechanical characteristics of the material of the product. Determination of the ratio of the amplitudes of the transmitted test article and the emitted acoustic vibrations can significantly increase their frequency. So, for film materials9 having a thickness of μm, according to expression (B), the frequency of acoustic vibrations should not exceed 60-120 kHz (the propagation velocity of acoustic vibrations in the material of the controlled product is assumed to be m / s), which is almost two orders of magnitude higher than the maximum possible frequency

in the prototype method. This allows us to increase the value of the first term - kh of the right-hand side of expression (3} also by two orders of magnitude and take it into account when determining the thickness of the controlled product, which eliminates the influence of the physicomechanical characteristics of the material of the controlled product on the measurement results. the phase difference of the received oscillations of the reference and measuring channels eliminates the influence of the variability of the parameters of the air

10

microcomputer 13 is sent to the data bus, which calculates the thickness of the controlled product by expression (12). Using the digital indicator 15, the calculation result is displayed — the thickness b of the item being monitored 16. In the memory of the microcomputer 13, the frequency f of acoustic vibrations and the speed with propagation of acoustic vibrations in the air are entered into the amp & constant. In the absence of the controlled product 16 in the measuring channel (before measurements) with

media (temperature, humidity) on a cutting adjustable phase shifter 9

thickness measurement result.

The device operates as follows.

Electric vibrations of frequency f

equalization of phase incursions s of the reference and measuring channels () j is performed, and with the help of an adjustable attenuator 10, equalization of the output AMS of the generator 1 of the stable 2 O-plate at the inputs of block 11 () is performed. At

Claims (2)

this according to expression (12). The claims the heats are amplified by the power amplifier 2 and fed to the first electrode of the radiating transducer 3. Acoustic waves emitted by the transducer 3 are received by the receiving transducer C. Electrical frequency vibrations f are also supplied to the radiating transducer 5 emitting acoustic vibrations, this according to expression (12). The claims 25 1. An ultrasonic method for determining the thickness of film products, which involves the emission and reception of sound signals in the reference radiation channel and the acquisition of ultrasound 35 signals received by the receiving transducer 6 through the controlled Oscillation from the output of the converter k through the amplifier 7 with the AGC are fed to the first input of the phase converter 8, the second input of which is fed from the electrical oscillations of the output of the converter 6 through an adjustable phase shifter 9. Electrical vibrations taken from the second electrode of the transducer 3, the amplitude of which is proportional to the amplitude of the acoustic oscillations emitted by the transducer 3, through an adjustable attenuator 10 are fed to one input Single ratio of 11, the other input of which receives the electrical waveform from the output transducer, the amplitude of which is proportional to the amplitude of received acoustic oscillations. The output voltage of block 11, equal to the ratio of the amplitudes of the received and emitted acoustic vibrations, is converted into a digital code using the ADC 12 and fed to the data bus of the microcomputer 13. The output voltage of the phase transducer 8 is equal to the phase difference of the pressed acoustic vibrations of the reference and measuring channels, is also converted into a digital code using the 1 k ADC and the input item: c. measuring khale, on the determination of the ratio of the amg. /. or d received and radiated kspsbynmm, measuring the phase difference i ole5ach.m.; op redele - n. and thickness ;; ontrol |. of the other product, taking into account the measured phase difference and the amplitude ratio, which requires that, in order to improve the measurement accuracy, the ratio of the amplitudes of the tested product and the emitted oscillations is determined, the difference oscillation phases in the reference and measuring channels, and the thickness of the controlled l products are determined from the expression (arctan b-i (f) .c and if h 27f. fifty 55 where W is the ratio of the amplitudes of the transmitted controlled product and the emitted oscillations; D (. | - the phase difference of the oscillations in  reference and measuring channels; the speed of propagation of acoustic vibrations in the yoz spirit; frequency of acoustic vibrations. with f 5139 10 microcomputer 13, which calculates the thickness of the controlled product by expression (12), onto the data bus. Using the digital indicator 15, the calculation result is displayed - the thickness b of the item being monitored 16. In the memory of the microcomputer 13, in the & id Ј constants are entered the frequency f of acoustic vibrations and the velocity from the propagation of acoustic vibrations in the air. In the absence of the monitored product 16 in the measuring channel (before measurements) with equalization of phase incursions s of the reference and measuring channels () j is performed, and with the help of an adjustable attenuator 10, equalization of am2O plates at the inputs of block 11 () is performed. At this according to expression (12). The claims 25 1. Ultrasonic method for determining the thickness of film products, which consists in the emission and reception of ultrasonic signals in the reference channel, the emission and reception of ultrasound 5 about signals that passed controlled product .: c. measuring khale, determining the ratio of amg. /. or d received and radiated kspsbynmm, measuring the phase difference i ole5ach.m.; defined - n. and thickness ;; ontrol |. of the other product, taking into account the measured phase difference and the ratio of amplitudes, which means that, in order to improve the accuracy of measurement, the ratio of the amplitudes of the tested product and the emitted oscillations is determined, the difference phases of oscillations in the reference and measuring channels, and the thickness of the controlled zo signals that passed control l products are determined from the expression (arctan b-i (f) .c and if h 27f. zo signals that passed controlled 0 5 where W is the ratio of the amplitudes of the transmitted controlled product and the emitted oscillations; D (. | - the phase difference of the oscillations in  reference and measuring channels; the speed of propagation of acoustic vibrations in yozdush; frequency of acoustic vibrations. with f 1535139 2. The method according to p. 1, about t l and h and more and with the fact that the frequency of acoustic vibrations is chosen from the ratio .0lrЈa, Mac propagation speed acoustic vibrations in the material of the controlled product; maximum possible thickness of the controlled product.