SU964525A2

SU964525A2 - Ultrasonic measuring device

Info

Publication number: SU964525A2
Application number: SU792840738A
Authority: SU
Inventors: Видас Антанович Сукацкас; Элигиюс Витауто Станкявичюс
Original assignee: Каунасский Политехнический Институт Им.Антанаса Снечкуса
Priority date: 1979-11-12
Filing date: 1979-11-12
Publication date: 1982-10-07

Description

(54) УЛЬТРАЗВУКОВОЕ ИЗМЕРИТЕЛЬНОЕ УСТРОЙСТВО(54) ULTRASONIC MEASURING DEVICE

Изобретение относитс к измерительной технике.This invention relates to a measurement technique.

По основному авт. св. 757975 известно ультразвуковое измерительное устройство, содержащее последовательно соединенные блок настройки частоты, генератор высокочастотного напр жени , камеру с двум преобразовател ми, усилитель, схему определени уровн 0,707, формирователь импульсов и селектор одиночных импульсов, а также смеситель, входы которого подключены к выходам генератора высокочастотного напр жени и усилител , а выход - к второму входу формировател импульсов, измерительный блок, состо щий из последовательно соединенных ключа, фильтра низкой частоты и схемы сравнени -усилени , и индикатор 1.According to the main author. St. 757975 An ultrasonic measuring device is known that contains a frequency tuner, a high-frequency voltage generator, a two-transducer chamber, an amplifier, a 0.707 level detection circuit, a pulse shaper, and a single pulse selector, as well as a mixer whose inputs are connected to the high-frequency generator outputs. the amplifier and the output to the second input of the pulse former, a measuring unit consisting of a series-connected key, a low-pass filter you -usileni and comparison circuits and LED 1.

Однако устройство обладает недостаточной точностью измерени .However, the device has insufficient measurement accuracy.

Целью изобретени вл етс повышение точнос.ти измерений..The aim of the invention is to improve the accuracy of these measurements.

Поставленна цель достигаетс тем, что.устройство снабжено последовательно соединенными вторым ключом и вторым фильтром низкой частоты , причем выход селектора одиночных импульсов подключен к управл ющемуThe goal is achieved by the fact that the device is equipped with a second key connected in series and a second low frequency filter, with the output of the single pulse selector connected to the control

входу второго ключа, который св зывает вход опорного напр жени схемысравнени -усилени с входом второго фильтра низкой частоты, а входы индикатора подключены к выходам первого и второго фильтров низкой частоты .the input of the second key, which connects the input of the reference voltage of the amplification circuit to the input of the second low-pass filter, and the indicator inputs are connected to the outputs of the first and second low-pass filters.

На фиг. 1 представлена структурна схема устройства; на фиг. 2 10 эпюры напр жений.FIG. 1 shows a block diagram of the device; in fig. 2 10 stress diagrams.

Устройство состоит из генератора 1, камеры 2, заполненной исследуемой средой, с излучающим 3 и приемным 4 пьезопреобразовател ми, усили5 тел 5, схемы 6 определени уровн 0,707, блока 7 настройки частоты, формировател 8 импульсов, селектора 9 одиночных импульсов, смесител 10, схемы 11 совпадени т-усилени , The device consists of a generator 1, a chamber 2 filled with the medium under study, with radiating 3 and receiving 4 piezotransducers, amplification of bodies 5, level 6 circuit 0.707, frequency tuning block 7, pulse generator 8, selector 9 single pulses, mixer 10, circuits 11 matches t-gain,

20 первого ключа 12, первого фильтра 13 низкой частоты,индикатора 14, второго ключа 15 и второго фильтра 16 низкой частоты,20 of the first key 12, the first low frequency filter 13, the indicator 14, the second key 15 and the second low frequency filter 16,

Claims

25 In FIG. 2, graph 17 shows the output voltage U of the reference-amplification circuit 11, the input voltage of the filter 13 (flashed) and its output voltage Uj. , Graph 18 shows the image-bearing voltage Ug, the input voltage of the filter 16 (shaded) and its output voltage U The device operates as follows 06 times. The high-frequency electrical signal produced by the generator I is converted by the converter 3 into ultrasonic waves propagating into the substance under study. in the chamber

2. Waves that have passed through the medium are transformed by a receiving transducer of gel 4 into an electrical signal amplified by an amplifier 5. Receiving transducer 4 is made wide-band and, if a comparator is studied, but a absorbing medium, is equipped with the necessary matching layers to eliminate a noticeable reverb. ultrasound in the camera. The frequency of the oscillator 1 is constantly changing in one direction or another under the influence of frequency tuning unit 7, due to the broadband nature of the receiving converter 4, its output voltage is modulated according to the law of the resonant characteristic of the best frequency converter 3 when the generator frequency changes near its resonance. The voltage of the converter 4 is maximum, when the frequency is equal to the resonant frequency of the | Emitting converter 3, and decreases when moving in any direction. When the voltage decreases to 0.707 of the maximum value, circuit b is activated and acts on tuning block 7. Through this block, the direction of frequency tuning is reversed. As a result, the frequency of the oscillator 1 is pumped within the band of the pass of the radiating transducer 3 Ultrasonic waves reach the converter 4 with late ut where. - distance between transducers, c - ultrasound velocity in the studied medium. At the output of the mixer 10, a beat signal is extracted, the period T of which is equal to where K is the frequency change rate. The former 8 generates pulses from the beat signal T. The selector 9 of single pulses sends one pulse from the former during each interval between two pulses schemes b. The density of this interval is equal to dR / K, where dP. Is the band of the emitting converter 3. the pulse of the selector 9 closes the keys 12 and 15 for the time T. The constant constituting the sequence of pulses of duration T, selected by the filter 13 (plot 17), is proportional to y - q t and d-; and - 1 4F ilTF where and., is the output detection of the comparison-amplification circuit 11. With a sufficiently large gain of the comparison circuit, the equilibrium Uo and is established. where Uo is the reference voltage, Kl is the constant. and .- and. from where the comparison gain circuit 11 provides a comparison of the input current from the reference voltage source Uo and the output current of the filter 13 and the amplification of a signal proportional to the difference of the currents. On the other hand, the density 3 of the test medium is expressed as where Kj is a constant. Comparison of formulas (2) and (3) implies where K is a constant. The reference voltage Up is also converted by means of a switch 15 to pulses (figure 18), the constant component of which is extracted by filter 16 and, together with the output voltage of filter å 13, is fed to indicator 14, a voltage ratio meter. The constant components of the pulse train with the duration T, selected by the low-frequency filters 13 and 16 are respectively proportional to cr 0 and Ux. Thus, on. The inputs of the DC voltage meter come from the low-frequency filters 13 and 16, and the ratio U (. proportional to the measured density p. As can be seen from the analysis of the graphs 17 and 18, the constant component K of the pulses of duration T formed from the voltage U (shaded in diagram 17, fig. 2), under the action of feedback, is maintained proportional to the reference voltage Uo, i.e. constant. When dP / t changes, the voltage changes accordingly. However, the voltage U undergoes fluctuations whose spectrum is beyond no filter skips 13 (high-frequency) and they are non-eliminated by feedback.In a known device, the indicator measures the voltage directly and, if the indicator is fast-acting (time: the measurements are marked dT), fluctuations lead to error. the most from the carrier and to the indicator with a long measurement time Tg - Fluctuation leads to a variation in the readings. In the proposed device, similar pulses are generated from the reference voltage UQ (Fig. 2, graph 18) and the ratio of the average component Up "with the voltage C; is measured; .. Thus, areas with uncontrolled fluctuations (open shading) are excluded from the measurement process. Moreover, the effect of smoothing filters is eliminated: the pulsations of both voltages have the same percentage, the law is eliminated, which increases the accuracy of measurements. The invention Ultrasonic measuring device according to ed. St. No. 757975, from that, in order to increase the measurement accuracy, it is equipped with serially connected second key and second low-pass filter, with the output of the single pulse selector connected to the control input of the second key, which connects the reference voltage input of the gain comparison circuit with the input of the second low-pass filter, and the indicator inputs are connected to the outputs of the first and second low-pass filters. Sources of information taken into account during the examination 1. USSR Author's Certificate No. 757975, cl. G 01 N 29/00, 1978.