SU444105A1 - Method for measuring the absorption coefficient of an acoustic signal - Google Patents

Description

The invention relates to the field of measurement technology and is intended to measure the absorption coefficient of an acoustic pulse in a test substance. The invention can be applied in the chemical, petrochemical, food and other industries.

A known method for determining the absorption coefficient of an acoustic signal by comparing the amplitudes of two pulses that passed acoustic paths of different lengths from the transmitting transducer to two receiving transducers and transformed into a periodic sequence of two pulses shifted in time. The magnitude of the absorption coefficient is determined from the measurement results by subsequent calculation.

However, the need to pre-measure amplitudes to calculate the absorption coefficient complicates the process.

The purpose of the invention is to automate the process of measuring the absorption coefficient of an acoustic signal.

This is achieved by the fact that pulses taken from receiving transducers are converted into constant voltages equal to the peak values of the amplitudes of the pulses, comparing these voltages with the reference exponentially varying voltage, and B is the moment of equality of the exponential voltage 2

Constant voltages produce short pulses for each of the voltages, the time interval between which is proportional to the absorption coefficient of the acoustic signal in the substance under study.

FIG. 1 shows a functional diagram of the implementation of the proposed method; in fig. 2 illustrates the principle of converting the ratio between the amplitudes of two pulses, which have passed the different acoustic path lengths from the transmitting transducer to the two receiving transducers, into a periodic sequence of two pulses shifted in time.

The device works as follows. Generator 1 generates a periodic sequence of short rectangular pulses that are fed to transmitting transducer 2, where they are converted into mechanical vibrations propagating in the test substance 3.

With the help of receiving converters 4 and 5, the energy of elastic oscillations is converted into electric pulses, which, after amplification by amplifiers 6 and 7, receive peak peak detectors 8 and 9. Constant voltages from the output of peak detectors equal to the peak values of the amplitudes of the pulses at the output of the amplifiers 6 and 7, the two inputs of the matching circuit 10 are supplied. An exponentially varying reference voltage from the exponential voltage generator 11 is supplied to the third output of the matching circuit. At the moment of equality of the exponential and each of the constant voltages, the coincidence circuit 10 produces short pulses, the time interval between which is proportional to the absorption coefficient of the acoustic pulse in the substance under study. The value of the time interval can be measured using any standard time interval meter 12. The voltage at the output of the generator 11 exponentially varying voltage can be written in the form - source e) where t /, cT. - voltage of the charging source; t is the time constant of the charge-discharge circuit RC. The stresses / - and Uz can be written respectively. "MI Ae-- and" 2 Aa-, where A is a coefficient proportional to - I n L - the distance between the receiving and transmitting transducers 4 and 5, respectively; a is the absorption coefficient. when, e - u, A. g-, t - n u, t / ist e - “, Ke - When t G, i.e. Logarithm of expression (1) and (2), we get: In A - a / In (Uist - In - pA.-L Subtracting expression (3) from expression (4) and designating T2-Ti as T, we have: - () - const, and a const t. Since T (Le) t. E. The absorption coefficient is permeable to the time interval between the pulses generated at times TI and Tg. Thus, the described amplitude-time conversion simplifies and automates the measurement process a, without requiring the use of either logarithmic amplifiers or limiting attenuators. Transformation facilitates the use of a computer to measure the absorption coefficient. Object of the Invention characterized in that in order to automate the process of measuring the absorption coefficient of an acoustic signal The pulses taken from the receiving transducers are converted into DC voltages equal to the peak values of the amplitudes of the pulses; these voltages are compared with the reference exponentially varying voltages, and at the instant that the exponential voltages are equal, each of the bare voltages is generated short pulses, the time interval between which is corona-directional, the absorption coefficient of the acoustic signal in the substance under study.