SU577452A1 - Digital device for checking ultrasonic wave propagation rate - Google Patents

Description

(54) DIGITAL DEVICE TO CONTROL THE SPEED OF SPREADING ULTRASOUND

selector, averaging unit and clock generator.

The drawing shows the structural scheme of the proposed device.

The device contains an automation unit 1, switch 2, generator 3, emitter 4, switch 5, amplifier 6, adjustable gain, receiver 7, trigger of duration 8, peak detector 9, comparing device Yu, emitter U amplifier 12, receiver 13, peak a detector 14, a clock pulse generator 15, a reversible counter 16, an averaging block 17, a coincidence circuit 18, a selector 19 and a reference oscillator 2O,

The device operates as follows: At the moment of switching on, the automation unit 1 generates a signal that sets the device nodes to their initial state. In this switch 2 to the output of the generator 3 under. emitter 4 is turned on, and the switch ohm 5 to the input of amplifier 6 with adjustable gain (receiver 7, trigger): duration 8 is set to the initial state, disconnecting the counting part of the device, and the information is reset to O,

Further operation of the device can be divided into two cycles: calibration of the amplification circuits and measurement of the propagation time of ultrasound.

Calibration of amplification circuits; The signal from the automation unit triggers generator 3. Thanks to a better-connected circuit, the output of amplifier 6 with an adjustable gain factor causes a signal to appear, the distance going through the sample {in direction: emitter 4 - receiver 7. This signal is converted by peak detector 9 and sent one of the inputs of the comparing device 10. The second signal of the automation unit connects the emitter 11 to the generator, and the input of the amplifier 12 - the receiver 13. The signal of the second peak detector 14 receives the signal that has passed the discussion -rj Ej (from The sensor 11 to the receiver 13 Since the distance 6 P. The amplitude of the sieve screens from the output of the amplifier b will be less than the amplitude of the signal from the amplifier 12. Thus, from the outputs of peak detectors, two voltages are applied to the inputs of the comparison device (Uj Ug), and at its output A control voltage appears, which, when applied to amplifier 6, increases its gain. The calibration process lasts until the amplitudes of the signals at the outputs of both amplifiers are balanced.

Measurement of the propagation time of ulch. At the moment of equality of stresses,

arriving from peak detectors, a pulse is output at the output of the comparison circuit. This pulse triggers the clock pulse generator 15, which sets the reversible counter 16 to the add mode and acts on the averaging block 17 The averaging block opens the element 18 and also, via the automatic block, connects the emitter 4 and the receiver 7. The first signal following the block the automation starts the generator, enters the averaging block and overturns the duration trigger, plugging in the measuring part of the device. Through the selector 19, the frequency of the filling frequency of the reference oscillator 20 begins to arrive at the input of the reversible counter. The signal passed through the sample and the amplified signal returns the trigger of duration to the initial state. With such a cutout, measurement and recording of the time of passage of the ultrasonic distance 2 ij into the counter take place. With the end of the tenth pulse, the averaging unit converts the reversible counter into the subtraction mode, and the automation unit connects to the output of the radiator generator 11, and 12 of the receiver 13. The time is measured for the passage of t2 by ultrasound of the distance E2. The tenth pulse of this series of ten measurements ensures the formation of the averaging signal of the result obtained .

As a result of the performed cycle of measurements of the reversible counter's display, the difference between the measured values tj and tj

-tii3M (ti ut) - (t.2-f ut) ti-t2.

The measurement result is characterized by a reduced magnitude of the systematic error. The magnitude of the random error is reduced by La by pre-processing the measurement results (averaging operation).

The calculation of the distance to determine the speed of ultrasound propagation is performed similarly (by the difference of two sample sizes - the length and width)

ism (e1 ± de) - (e2 ± le) e1-e2.

The value of ultrasound velocity determined by the well-known formula

V- ISM

  meas

Claims (2)

1. Author's certificate number 391466, cl. G 01 N 29/00, 1973. 2. Author's certificate number 317968, cl. G 01 N 29/00, 1971.