SU1320731A1 - Eddy current flow detector - Google Patents

Abstract

This invention relates to the inspection of electrically conductive products by an electromagnetic method. The goal is to increase the reliability of controls by better tuning the effect of the gap and electromagnetic fields, which is achieved due to the automatic maintenance of the operating mode of the measuring oscillator (AG), which is close to the generation failure mode. Automatic adjustment of the sensitivity to the gap is determined by changing the voltage on the control unit in the measuring AG with the MOULbro value, which includes the comparison unit 1, the counter 14 and the digital-analog converter 16. The frequency of adjustment of the measuring AG determines the clock generator 15. The power of measuring AG is carried out from a controlled voltage regulator 2. The flaw detector uses a pulsed excitation method of measuring AG, the oscillating circuit of which includes an eddy current transducer 4; the sampling frequency of the measuring AG generates a wired generator 1. The information parameter about the state of the test object is the time interval for establishing high-frequency oscillations of the measuring AG. The amnite detector 5, the comparator 6, the coincidence unit 7, the pulse generator 8, the counter 9 and the one-oscillator 10 convert the duration of the establishment of high-frequency oscillations of the measuring AG into a binary code. The information is reflected in the indicator 13. 1 Il. OS

Description

The invention relates to instrumentation technology and can be used for the inspection of electrically conductive products by an electromagnetic method.

The aim of the invention is to increase the reliability of control due to the best detuning of the effect on the control result of the gap between the transducer and the product and electromagnetic interference.

The drawing shows a block diagram of a vortex flaw detector.

The flaw detector consists of a master oscillator 1, a controlled voltage regulator 2, a measuring oscillator 3, an eddy current transducer 4, an amplitude detector 5, a comparator 6, a coincidence unit 7, a second counter generator 9, a single-oscillator 10, a comparator unit 11, a code generator 12 indicator 13, the first counter 14, the clock generator 15, a digital-to-analog converter 16.

The master oscillator 1 is connected in parallel to the third input of the coincidence unit 7, to the input of the one-vibrator 10, the third input of the comparison unit 11 and the control input of the voltage regulator 2, the output of which is connected to the second input (power supply) of the measuring auto-oscillator 3, to the oscillating circuit which includes an eddy current transducer 4. To the output of the measuring oscillator 3, connected in series are an amplitude detector 5 and a comparator 6, the output of which is connected to the first input of the coincidence unit 7. The pulse generator 8 is connected to the second input of the coincidence unit 7, the output of the coincidence unit 7 to the second input of the second counter 9, to the first input of which the output of the one-vibrator 10 is connected. The output of the counter 9 is connected to the first input of the comparator 11, the second input of which is the connection} ; en with the shaper 12 code. The output of the comparison unit i1 is connected to the indicator 13 and to the first input of the first counter 14, to the second input of which the clock generator 15 is connected. The output of the counter 14 is connected to the input of the digital-to-analog converter 16, the output of which is connected to the control input of the measuring auto-generator 3.

In the eddy current detector, a pulse excitation method is implemented for the measuring oscillator 3, in the oscillatory circuit of which is a pair. A metric eddy current transducer 4 interacting with an object of control (not shown). P} as the ip formatization parameter about the state of the object being monitored, the duration of establishment of the oscillation of the oscillator oscillator by the KOMacTOTiibix is used. In the flaw detector, the operating mode of the measuring autogenerator is 1 ora. close to the generation stall mode.

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The flaw detector works in the following way.

The required operating mode of the measuring autogenerator 3 is established by varying the amplitude of the power-supply pulses and the measuring auto-oscillator, coming from the controlled voltage regulator 2. The sampling frequency of the measuring autogenerator is determined by the master oscillator I, which during the operation of the measuring autogenerator 3 locks the comparison unit 11 and opens the matching unit 7. At this time, the second counter 9 receives signals from the generator 8 pulses. At the same time, the one-shot 10 generates a short pulse setting the second counter 9 to zero. The process of measuring the time interval for establishing high-frequency oscillations begins. After the amplitude of the high-frequency signal has reached the threshold level, the comparator 6 is triggered and at its output it is set as "O, which closes the coincidence unit 7. Information about the number of pulses transmitted to the second counter 9 in a binary-parallel code is fed to the comparison unit 11. The second counter 9 stores information until the next reset pulse. After the measurement process is completed, the master oscillator 1 closes the coincidence unit 7 and opens the comparison unit 11, which matches the information supplied to the second counter 9, with information from the code generator 12. Depending on the ratio of the codes stored in the counter 9 and the shaper 12 of the code, various signals appear on the three outputs of the comparison unit 11, which control the indicator 13.

In the absence of defects on the test surface and the minimum gap between the transducer of the control object from the second counter 9, a code is received that corresponds to the code received from the driver 12 of the code. At the output of the comparison unit P, an impulse appears, and the LED "NORM of the indicator 13 lights up.

The appearance of a crack under the converter m 4 leads to an increase in the active insertion resistance of the eddy current probe, a decrease in the equivalent resistance of the resonant circuit, a decrease in amplitude, and an increase in the time for establishing high-frequency oscillations. The code at the output of the second counter 9 is greater than the code of the driver of the 12 code. A pulse appears at the output of the comparator unit 11, the LED DEFECT of the indicator 13 lights up. From this output of the comparator unit 11, pulses can also be fed to any sorting device or defectometer.

Increasing the gap between the transducer and the controlled surface reduces the active insertion resistance, which leads to a reduction in the time for establishing high-frequency oscillations of the measuring oscillator 3. The code of the second counter 9 becomes less than the code of the driver 12, and the output of the comparison unit 11 has an impulse the first input of the first counter 14 and the indicator 13, in which the LED "CLEAR. At the output of the digital-to-analog converter 16, a negative polarity voltage appears, which is supplied to the control input of the measuring oscillator 3.

The volt-ampere characteristic of the active element of the autogenerator 3 is chosen such that as the voltage increases from the digital-to-analog converter, its negative resistance decreases, which leads to a decrease in the amplitude of oscillations and an increase in the time for establishing oscillations. This preserves the duration of the establishment of oscillations.

The increase in the number of pulses in the first counter 14 occurs until the code at the output of the second counter 9 becomes equal to the code of the driver 12 codes. The flaw detector is reset to its initial state at the command of the clock generator 15. After this, the process of automatic adjustment of the flaw detector sensitivity is resumed. Thus, the sensitivity of the eddy-current flaw detector is adjusted when the gap between the transducer 2 and the test object changes randomly.

Thus, in the flaw detector, the likelihood of detecting defects when the gap between the transducer and the test object changes is increased by bringing the measuring oscillator to maximum sensitivity, close to the generation breakdown mode, the probability of an eddy current flaw detector failing due to industrial noise, by converting the duration of the establishment of oscillations (associated with the parameters of the defect) into a code.

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Claims (1)

Invention Formula five An eddy current flaw detector containing a measuring autogenerator in series with an eddy current transducer included in its oscillating circuit, an amplitude detector and a comparator, a pulse generator, an indicator and a serially connected first counter and a digital-to-analog converter connected to the control input of the measuring autogenerator, differing from , in order to increase the reliability of control, it is equipped with series-connected master oscillator, single vibrator, second circuit with a pick and a comparison unit, the output of which is connected to the indicator and the first input of the first counter, a coincidence unit, the first input of which is connected to the output of the comparator, the second input is connected to the pulse generator, and the output to the second input of the second counter, Q shaper code, the output of which is connected to the second input of the comparator unit, a clock generator connected to the second input of the first counter, controlled by a voltage regulator, connected between the output of the master oscillator and 5 with the power bus of the measuring autogenerator, and the output of the master oscillator is connected to the third inputs of the comparator unit and the coincidence unit, respectively.