SU542134A1 - Device for measuring ultrasonic absorption coefficient - Google Patents

Description

DEVICE FOR MEASUREMENT OF COEFFICIENT

(54) ULTRASOUND ABSORPTION

This invention relates to ultrasound absorption meters and can be used to study the properties or analysis of liquids or gases.

Acoustic interferometers 1 are widely used to measure the absorption coefficient of ultrasound. The absorption coefficient is determined by the measured value of a set of maximum and minimum voltages at the output of the electro-acoustic path of the interferometer.

The closest to the invention in its technical essence is a device for measuring the absorption coefficient of ultrasound, containing the electroacoustic path of the interferometer, consisting of a generator of electrical oscillations of stable frequency and an acoustic chamber of variable length, the output of which is connected in series with an amplifier-detector and recording unit 2.

However, measurement using the specified device requires a large number of manual operations and calculations, which reduces the speed of measurements.

The purpose of the invention is to automate the measurement process.

This goal is achieved by the fact that the registering unit is implemented in the form of a unipolar peak positive polarity detector, a unipolar peak negative polarity detector with a positive bias and a two-polar peak detector, between the outputs of a single polar detector and at the output of the bipolar detector with a division ratio of 1: 2, the outputs of the voltage dividers are connected to the inputs of the DC ratio meter, the common input of which is connected to the output of the unipolar peak negative polarity detector with a positive bias.

FIG. 1 shows a block diagram of the device, and FIG. 2 - stress diagrams for his work.

A stable frequency electrical oscillation generator 1 is connected to a piezo-emitter 2 located in the chamber of interferometer 3. Piezo receiver 4, moved by displacement unit 5, is connected to the input of amplifier-detector 6. Elements 1-5 constitute the electroacoustic path of a variable length interferometer. The output of the amplifier - detector 6 is connected to a unipolar peak detector 7 of positive polarity, also to a unipolar peak detector 8 of negative polarity, connected to the source 9 of a positive mixing voltage. To the melody, the outputs of the detectors 7 and 8 are connected to a divider 10 with a division ratio of 1: 2. The output of amplifier - detector 6 is also connected to a two-pole peak detector 11, loaded by a divider 12 with a division factor of 1: 2. The outputs of dividers 10 and 12 are connected to separate inputs of the meter 13 of the ratio of direct voltages, for example, a ratiometric measuring device. The output of the detector 8 is connected to the common ungrounded input of the ratio meter 13.

The device works as follows.

The device is powered on, after which the generator 1 begins to output the high frequency voltage applied to the piezo emitter 2. The piezoelectric generator 2 emits ultrasonic waves propagating in the test substance placed in the chamber of the interferometer 3. Ultrasound is partially reflected from the piezoelectric receiver 4 and is partially converted by it into electrical oscillations amplified and detected by the amplifier-detector b. With the start of measurement, a displacement unit is started, which begins to bring together piezotransducers 2 and 4. An alternating voltage develops on the plates of piezopath receiver 4; The minima are obtained with the length of the medium column, departing from a quarter-wavelength ultrasound. A variable voltage envelope is made by a detector constituting a bip block of positive polarity at the output of block b. The output voltage of the amplifier-detector b is shown in FIG. 2a

At the output of the peak detector 7, a positive voltage is proportional to the maximum voltage module of the piezo receiver 4 (Fig. 26). At the output of the peak detector 8, since it is connected to the source 9 of the bias voltage, the magnitude of which is greater than the maximum minimum of the output voltage of the block b and one polarity with the ladies. positive voltage is allocated, proportional to the minimum voltage Umi and piezo receiver 4 (Fig. 26). At the same time, the voltage between the outputs of the divider 10 and the detector 8 is equal to Umax-mm. At the output of the two-pole detector 1

2

there is a negative voltage proportional to the difference of the maximum and minimum voltages

wives - (Umax - Umin). The output voltage dc itel 12 is equal to JZma. - 2 c). The voltage between the outputs of the detector 8 and the divider 12 is equal to:

-Tg J: -

mtn a: m.a / 7

(Fig. 2). The meter 13 of the ratio of direct voltages with I-grounded inputs will show the ratio of both input voltages, i.e. max - Unxin

to.h tp1g1

With a decrease in the distance between the transducers, the output voltages of the detectors 7 and 11 increase in absolute value, and the output voltage of the detector 8 relative to the housing slightly increases. The ultrasound absorption is determined by the increment of the logarithm of the readings of the ratio meter 13, corresponding to a given change in the distance between transducers 2 and 4.

In the case of negative polarity of the output voltage of the amplifier-detector b, the polarities of the detectors 7, 8, 11 and the source 9 of the bias must be reversed.

Claims (2)

1.A. E. Kolesnikov Ultrasonic Measurement Ed. Standards M. 1970, pp. 96-97. 2.U. Mason per. from English .. Methods and devices for ultrasound research. Ed. World 1966, T. L Ch.A., pp. 339-343. L :: C3 fu.