SU1465828A1 - Device for locating a dynamically unstable contact - Google Patents

Abstract

The invention relates to the field of instrumentation technology. - The device contains a receiving sensor 1, a high-frequency amplifier 2, a detector 3 and a low-frequency amplifier 4, recording the radio frequency signal of a defective contact. The reference signal is generated by an acoustic transducer 5, a low-frequency amplifier 6 and a phase shifter 7. Correlation processing of the signal using a multiplier 8 and an integrator 9 makes it possible to increase the detection accuracy of a dynamically unstable contact. 1 il.

Description

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The invention relates to instrumentation engineering and can be used to create devices for monitoring the integrity of electrical circuits.

The purpose of the invention is to increase the reliability of determining the location of dynamically unstable contact i by increasing the noise immunity.

The drawing shows a functional diagram of the proposed device for determining the location of a dynamically unstable contact.

Device -determining the location of a dynamically unstable contact i contains a receiving sensor 1, for example, an inductive transducer, a high-frequency amplifier 2, a detector 3, a first low-frequency amplifier 4, an acoustic transducer 5, a second low-frequency amplifier 6, a phase shifter 7, a multiplier 8. integrator 9 , threshold element 10 and indicator 11.

The receiving sensor I is located in the f near zone of radiation of the control object 12 (at a distance of 1-10 mm above its elements). The output of the receiving sensor 1 is connected to the input of a series-connected amplifier 2 high frequency, detector 3 and the first amplifier 4 low frequency. The acoustic transducer 5 is mechanically secured (for example, using a miniature clamp) on the edge of the control object 12 (printed circuit board), free from the elements. Dp this requires a plot of 15x5 mm. The output of the acoustic transducer 5 is connected to the input of a serially connected second amplifier 6 1 CLUTCH frequency and phase shifter 7. The output of the phase shifter 7 and the output of the first amplifier 4 of low frequency are connected to the corresponding powers of multiplier 8, and the output of the multiplier is connected to the series-connected integrator 9, element 10 and indicator 11.

The device works as follows.

The control object 12 (printed circuit board) is in working condition (power supply voltage is applied) and is subjected to mechanical action with the help of a device that creates a normalized impact. At the same time, the mechanical vibrations propagating along the monitored board are created in the acoustic transducer 5 signal and at the same time, if there is a dynamically unstable vyntakt in the control object, they stimulate electromagnetic radiation into the ether. This radiation is perceived by the receiving sensor 1, amplified by the high frequency amplifier 2, amplitude detected by the detector 3 and amplified by the low frequency amplifier 4. From the output of the low-frequency amplifier 4, a signal is fed to one of the inputs of the multiplier 8, to the second input of which comes an amplified and phase-out signal from the acoustic transducer 5. Thus, the multiplier 8 performs the analog multiplication operation of the high-frequency signal induced in the receiving sensor 1 ( amplified and detected), and the acoustic signal received at the input of the acoustic transducer 5 (amplified and phase-shifted). The product of these signals from the output of multiplication 8 is fed to the input of the integrator 9, which serves to smooth out the noise and accumulate useful information. From the output of the integrator 9 signal is fed to the threshold device, which serves to limit the level of interference. From the output of the threshold device 10, a signal is applied to the indicator 11.

In the general case, a signal is received at the input of the receiving sensor 1, which consists of an additive mixture of the useful signal u (t) and a random noise (t). Therefore, there is a signal at the integrator output, which is determined by the expression

i

and K j u (t) +2 (t) -v (t) dt, (1)

where K is a coefficient that takes into account the transformation of each of the signals arriving at the inputs of the multiplier due to passing through the circuits of the device;

V (t) is the signal of the acoustic transducer;

t is the correlation time, which is determined by the duration of the own continuous oscillations of the printed circuit board.

Expression (1) decomposes into sumd two integrals

t v

and K ((U (t) V (t) dt + j (t) X

. (/

t-l

e-X V (t) dt | .

(2)

Since the signal at the output of the acoustic transducer 5 is correlated with the useful signal emitted on the air by a dynamically unstable contact and is not correlated with interference, and the second integral in expression (2) is zero, only the useful signal is present at the integrator output. Since the correlation time is determined by the duration of the mechanical oscillations of the printed circuit board, the signal in the pause mode between shock effects is practically absent and determines only its own noise

devices that

I

Phaser 7, included in the channel component of the acoustic signal processing, serves to obtain the maximum: correlation coefficient. The phase angle of the acoustic signal, carried out by the phase shifter 7, is chosen so that in the presence of a useful signal and random interference at the input of the receiving sensor

Claims (1)

to obtain the maximum signal-to-noise ratio at the output of the integrator 9. Formula of the invention A device for determining the location of a dynamically unstable contact, containing an indicator, a receiving sensor connected to the input of a high-frequency amplifier, the output of which is connected through a detector to the input of a low-frequency amplifier, that, in order to increase the accuracy of determining the location of dynamically unstable contact by increasing noise immunity, an acoustic transform is introduced into it spruce, a second low-frequency amplifier, the Optional zovraschatel, multiplier, integration. A 20 torus and a threshold element, an acoustic transducer is installed at the control object, the output of the acoustic transducer is connected to the inputs of a series-connected second 25 low-frequency amplifier and phase shifter, the output of the phase-shifter and the output of the first low-frequency amplifier are connected respectively to the first and second multiplier inputs, and the output 30 is connected to the input of the integrator, the output of which is connected in series with a threshold element and an indicator.