SU757974A1 - Automatic meter of reflection coefficient of acoustic signals from piezotransducer - Google Patents

Description

The invention relates to the technical acoustics and can be used to determine the acoustic characteristics of the equipment with! the development of electro-acoustic paths of ultrasonic instrumentation.

Known meter reflectance of ultrasonic waves from. 1 piezoelectric transducer [1], contains _;

ultrasonic signal emitter, a piezotransducer under study, a reflector, an indicator, a radio pulse generator, a modulator, and {a switch. The device does not allow to automate the measurement process in a wide range of frequencies "

The closest to the technical 2 entity is an automatic meter of the reflection coefficient of acoustic signals from a piezoelectric transducer ^ 2 ^, containing a series-connected pulse 2 \ oscillator ?, oscillating frequency generator, a switch, a selector of reflected pulses, a peak detector, a voltage ratio meter and an indicator; scanner, outputs 3,

2

They are connected to other inputs of the oscillating frequency generator and the indicator, a delay circuit connected between the output of the pulse generator and another input of the selector switch of the reflected pulses, a piezo emitter connected to the output of the oscillating frequency generator, and the piezoelectric generator under study.

The disadvantages of the meter are low performance and measurement accuracy. This is because in order to achieve a sufficiently high

5 measurement accuracy requires adjustment of the electroacoustic system consisting of a reflector, a two-way piezo emitter and a piezoelectric transducer under investigation, which is

θ difficult and time consuming process. Due to the unequal absorption of acoustic signals in two channels of the electro-acoustic path, a measurement error appears. This error increases when working in

highly absorbing media and radio pulses with a long duration, i.e.

at long distances reflector and

the piezoelectric transducer from

η piezo emitter.

3

757974

four

The aim of the invention is to improve the accuracy and simplify the measurement process.

This goal is achieved by the fact that a second peak detector and a low frequency filter are inserted into the meter, the second peak detector and a low frequency filter are connected in series, the input of the second peak detector is connected to the output of the first peak detector, and the output of the low frequency filter is connected to the second input of the meter stress relationship

The invention is illustrated in the drawing, which shows a block diagram of the meter.

The meter contains a pulse generator 1, the output of which is connected to the input of the oscillating frequency generator 2, another input of which is connected to the output of the sweep unit 3, the output of which is connected to the switch 4, delay circuit 5 connected between the output of the pulse generator 1 and the input of the pulse reflection selector b, another input of which is connected to the output of the switch 4, the output of which is connected to a circuit of the first peak detector 7, the second peak detector 8 and the low-frequency filter 9 connected in series, the ratio meter 10 voltage, the inputs of which are connected to the outputs of the first peak detector 7 and low-frequency filter 9, the output of which is connected to the input of the indicator 11, another input connected to the output of the sweep unit 3, studied by a piezoelectric transducer 12 installed in parallel to the radiating surface of the piezo-emitter 13 in the acoustic pool 14, the output of the oscillator 2 oscillating frequency is connected to the radiating piezo emitter 13.

The meter works as follows. Radio pulses from the output of the oscillating frequency generator 2 are fed to a piezo emitter 13, with which an acoustic signal is emitted towards the piezo transducer 12, which, after being reflected from the piezo transducer 12, is received again by the piezo emitter 13. The reflected signal through the switch 4, the select switch b and the reflected pulses the first peak detector 7 enters the first input of the voltage ratio meter 10, and the 8th low-frequency filter 9 through the second peak detector to the second input of the voltage ratio meter 10 . The time constant of the second peak detector 8 is significantly greater than that of the first. Therefore, at its output, the signal is proportional to the maximum value of the reflected signal during the time during which the frequency of the oscillator 2 of the sweeping frequency changes from minimum to maximum. Since the reflection coefficient from the piezoelectric transducer 12 in the field of even harmonics is equal to one, the voltage at the output of the low-frequency filter 9 is equal to the magnitude of the signal reflected from the ideal reflector. The voltage at the output of the first peak detector 7, which has a small time constant, at each time instant corresponds to the magnitude of the signal reflected from the piezoelectric transducer 12 being investigated. Therefore, the voltage at the output of the voltage ratio meter 10 is proportional to the reflection coefficient. The sweep of the indicator 11 is carried out synchronously with the modulation voltage of the oscillator 2 oscillating frequency. On the screens of indicator 11, a curve of the dependence of the reflection coefficient on the frequency is obtained.

Claims (1)

Claim An automatic reflector meter for acoustic signals from a piezoelectric transducer, containing a series-connected pulse generator, a sweeping frequency generator, a switch, a reflected pulse selector, a peak detector, a voltage ratio meter and an indicator, a sweep unit, whose outputs are connected to other inputs of the sweeping frequency generator and indicator, a delay circuit connected between the output of the pulse generator and another input of the selector of reflected pulses, a piezoelectric transducer, to the output of the oscillating frequency generator, and the piezotransducer under investigation, which differs from me by the fact that, in order to improve the accuracy and simplify the measurement process, a second peak detector and a low frequency filter are inserted into it, while the second peak detector and a low frequency filter are connected in series, the input of the second peak detector is connected to the output of the first peak detector, and the output of the low-pass filter is connected to the second input of the voltage ratio meter.