SU1428939A1 - Ultrasonic vibration meter - Google Patents

Abstract

The invention relates to a measurement technique, namely, devices for measuring the amplitude of mechanical oscillations of an object, and can be used to measure the relative vibratory transmission of metallic or metallized surfaces of various objects, such as ultrasonic transducers. The aim of the invention is to improve the measurement accuracy by calibrating the device during the measurement process. This goal is achieved by introducing a capacitor, a switch and an amplitude detector. The signal from the oscillator, which includes a parametric displacement sensor and a capacitor, is fed to the discriminator amplifier and then to the frequency detector. The switch periodically shunts condensate p, which causes a modulation of the signal on the input of the frequency detector. At the output of the first amplitude detector, the signal is proportional to the measured oscillation, and at the output of the second amplitude detector, the magnitude of the equivalent change in the gap determined by the capacitance of the capacitor. 1 il. with S (L

Description

The invention relates to a measurement technique, namely, devices for measuring the amplitude of mechanical vibrations of an object, and can be used to measure relative vibration displacements, metal or metallized surfaces of various objects, such as ultrasonic transducers.

The purpose of the invention is to improve the accuracy of measurements.

The drawing shows a structural diagram of an ultrasonic vibrometer

The ultrasonic vibrometer contains a series-connected auto-generator I5 amplifier-discriminator 2, frequency detector 3, high-pass filter 4, first amplitude detector 5, low-pass filter 6, whose input is connected to the output of frequency detector 3, second amplitude detector 7, which input i connected to the output of the low-pass filter 6, a divider 8, the inputs of which are connected to the output of the first detector 5, and the output of the second detector 7, an indicator 9 connected to the output of the divider 8, a capacitor 10 connected to the auto-oscillator 1 The sequence with the parametric displacement sensor 11 and the capacitive type switch 12 connected in parallel with capacitor 10.

. The displacement sensor 11 is a metal plate mounted at a distance from the oscillating surface. Switch 12 periodically at a low frequency) closes the contacts of the capacitor 10. As a result, the sensor is periodically connected either directly to the oscillator circuit, or through the 0o capacitor

Ultrasonic vibrometer works as follows

In accordance with the change in the gap between the sensor 1 and the oscillating surface, the sensor capacitance changes, which leads to a change in the instantaneous frequency value of the signal of the oscillator 1, since the capacitance of the sensor 11 is included in the oscillator circuit of the oscillator.

The frequency-modulated signal from the output of the oscillator 1 is fed to

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the input of the amplifier-discriminator 2, in which it is amplified and the elimination of the accompanying amplitude modulation. From the output of the amplifier-discriminator, the signal is fed to the input of the frequency detector 3, where it is detected. Thus, a change in the capacitance of the sensor 11 is converted into an electrical signal.

The inclusion of a capacitor with capacitance C in series with the sensor is equivalent to increasing the gap between the sensor plate and the object's surface by the Ad value, which is equal to S С

As can be seen from the formula, the magnitude of the equivalent change in the gap does not depend on the size of the gap between the sensor and the surface of the object, nor on the sensitivity of the circuit, but is determined only by the area S of the working surface of the sensor, the capacitance of the capacitor C and the relative dielectric constant of the medium. do not change during the measurement process, the equivalent gap change is used as a reference for measuring the amplitude of ultrasonic vibrations.

When the switch operates, two signals are present at the output of the frequency detector: an alternating voltage of ultrasonic frequency, the amplitude of which is proportional to the amplitude of the ultrasonic oscillations of the object, and rectangular pulses, whose amplitude is proportional to the value of the change in the & d gap.

Ultrasonic signal is detected by high-pass filter 4 and detected by first amplitude detector 5e. Low-frequency square impulses are filtered out by low-pass filter 6 and detected by second amplitude detector 7. From the output of the first amplitude detector 5, the voltage proportional to the amplitude of ultrasonic vibrations is transmitted to the first half of the detector. divider 8. From the output of the second amplitude detector 7, a voltage proportional to the magnitude of the equivalent variation of the clearance Dyo is applied to the second input of the divider.

Thus, the output voltage of the divider, which is fed to the indicator 9, is the result of the comparison of the measured amplitude with the reference and does not depend on the size of the gap between the sensor and the object, nor on the sensitivity of the frequency detector and the entire previous circuit.

Claims (1)

Invention Formula An ultrasonic vibrometer containing a series-connected auto-oscillator, an amplifier-discriminator, a frequency detector, a high-pass filter, the first amplitude detector, a divider, the first input of which is connected to the output of the first amplitude detector, and an indicator, as well as a low-frequency filter, the input of which is connected to the output of the frequency detector, and a parametric displacement sensor, characterized in that, in order to improve measurement accuracy, it is equipped with a capacitor connected between a parametric displacement sensor of capacitive type and an oscillator, a switch connected in parallel to the capacitor, and a second amplitude detector, the input of which is connected to the output of the low-pass filter and the output to the second input of the divider. g / gp LI -J