SU1640625A1 - Device for pulsed eddy current testing - Google Patents

Abstract

The invention relates to non-destructive testing and can be used to measure the electrophysical parameters of electrically conductive products. The purpose of the invention is to increase the reliability by suppressing the influence of the variation of the gap between the test object and the transducer of a pulsed eddy current device at all possible values of the specific electrical conductivity of the material of the test object. Under the influence of the excitation pulse generator, useful signals are generated at the output of the converter. They are fed to the subtraction unit, which forms the resulting signal. The shape of the resulting signal is compared to a given waveform for a given material. The series of measurements are statistically processed and the average value of the time interval for this series of measurements is recorded on the indicator, according to which the controlled parameter is judged. 3 il.

Description

The invention relates to non-destructive testing and can be used to measure the electrophysical parameters of electrically conductive products.

The aim of the invention is to increase the reliability by reducing the influence of the variation of the gap between the test object and the transducer of a pulsed eddy current device for all possible values of the specific electrical conductivity of the material of the control volume.

FIG. 1 is a block diagram of a device for pulsed eddy current testing; in fig. 2 and 3 are diagrams explaining the principle of operation of the device.

The device contains (Fig. 1) a pulse generator 1, the first output of which is connected to the input of the vortex converter 2, and the second output with a synchronizer, the outputs of the converter 2 are connected to the inputs of the subtracting unit 3, the output of which is connected to the input of the amplifier 4, generator 5

clock pulses, coincidence circuit 6, pulse counter 7, indicator 8, memory block 9, digital-to-analog converter 10, comparator 11, useful signal extraction circuit 12, synchronizer 13, pulse driver 14, register 15 and microcomputer 16.

The amplifier output is connected to the second input of a controlled comparator 11, the output of which is connected to the first input of the useful signal extraction circuit 12, the first output of which is connected to the second output of the synchronizer 13, the fourth and first outputs of which are connected to the first and second inputs of the pulse former 14, the output of which connected to the second input of the matching circuit 6, the output of the clock pulse generator 5 is connected to the first input of the matching circuit 6, the output of which is connected to the first input of the pulse counter 7, the third synchronizer output 13 is connected to the second input of the counter.J

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pulses, the first output of which is connected to the input of a programmable memory device 9, the output of which is connected to the input of a high-speed digital-analog converter 10, the output of which is connected to the first input of the comparator 11 of the control, the second output of the counter of pulses 7 is connected to the first input of the register 15, the fifth output of the synchronizer 13 connected to the second input of the register 15, the output of which is connected to the first input of the microcomputer 16, the sixth output of the synchronizer 13 is connected to the second input of the register 15, the output of which is connected to the first the input of the microcomputer 16, the sixth output of the synchronizer 13 is connected to the second input of the microcomputer 16, the output of which is connected to the input of the indicator 8.

The device works as follows.

The excitation pulse generator 1 produces rectangular voltage pulses {Fig. 2, plot 17). They are fed to the exciting winding of the converter 2 and the second input of the synchronizer 13. With the voltage pulse supplied to the exciting winding of the converter 2, a current flows through it (Fig. 2, plot 18). If the eddy current transducer 2 does not interact with the control object, the emf induced on its windings are equal to each other (Fig. 2, plots 19a and 20a). In this case, the signals at the outputs of the subtractive unit 3 and the amplifier 4 are missing (Fig. 2, plot 21a). When the eddy current transducer 2 is installed on the control object, the equality between the EMF of the measuring windings under the influence of the field of the eddy currents induced in the object material (Fig. 2, plots 196 and 206) and the outputs of the subtracting unit 3 and amplifier 4 receive a difference signal ( Fig. 2, plot 216), which is fed to the second input of the comparator 11.

Upon completion of the impact of the voltage pulse from the generator 1, the synchronization unit 13 begins to generate control pulses that synchronize the operation of the measuring and indicator parts of the device. The first two control signals produced by the synchronizer 13 are a square gating pulse (Fig. 3, plot 29) supplied to the second input of the useful signal extraction circuit 12, as well as a pulse (Fig. 2, plot 22). at the first input shaper 14 pulses.

With the arrival of a pulse at the first input of the driver 14, the last one, which is a trigger, goes into a state when a voltage appears at its output. This voltage (Fig. 2, plot 24) is applied to the second input of coincidence circuit 6. Since clock pulses (Fig. 2, plot 23) constantly go to the first input of circuit 6 from a quartz oscillator 5 clocks operating in the continuous generation mode, then counting pulses begin to enter to the first input of pulse counter 7 (Fig. 2, plot 25).

In accordance with the counted count of 7 pulses, the number of counting pulses of a programmable storage device 9 through a high-speed

5, a digital-to-analog converter 10 forms the law of change of the reference voltage at the first input required for measuring the time values of the nodal points introduced into the converter 2 signals.

0 controlled comparator 11 (Fig. 2, plot 26).

When converter 2 interacts with the metal of the control object, from amplifier 4 to the second input of comparator 11

5, a differential signal is applied (Fig. 2, plot 216). Depending on the parameters of the differential signal at the second input and the level of the reference voltage at the first input (Fig. 3, plot 276), the output of the comparator 11 causes one or more square pulses (Fig. 3, plot 286) to enter to the first input of the useful signal extraction circuit 12. Of these pulses (Fig. 3, plot 296) by circuit 12 to the first input

5, the synchronizer 13 transmits only that one (FIG. 3, plot 306) coincides in time with the gating (FIG. 3, plot 29). The temporal position of the trailing edge of the pulse transmitted by the circuit 12 (Fig. 3, plot 306) is determined by the temporal position of the nodal point of the signal of the transducer 2.

Starting from the temporary position of the falling edge selected by the pulse 12 circuit 5, the synchronizer 13 forms a new series of three control pulses. The first control pulse (Fig. 3, plot 316) is supplied from the fourth output of the synchronizer 13 to the second input of the driver 14. With its arrival, the voltage at the output of the driver 14, and therefore, at the second input of the coincidence circuit 6, becomes zero (FIG 3, plot 326). The clock pulses from the generator 5 cease to flow through the coincidence circuit 6 to the first input of the counter 7 (Fig. 3, plot 336).

The second (Fig. 3, plot 346) and the third (Fig. 3, plot 366) of the series control pulses come from the fifth and sixth outputs

synchronizer 13, respectively, to the second inputs of the register 15 and the microcomputer 16. With their arrival, information is overwritten from the second output of the counter 7 to the register 15 and from the last to the microcomputer 16. The counter is reset by a pulse applied to its second input (FIG. 3, plot 35) generated by the synchronizer 13 along the trailing edge of the strobe pulse (Fig. 3, plot 29). With each new pulse produced by the generator 1, the device’s cycle of measuring the time of the signal nodal point is repeated.

In the absence of a signal at the output of the amplifier 4, i.e. when transducer 2 does not interact with the control object, the pulse duration at the output of shaper 14 (Fig. 3, plot 32a) is determined by the duration of the gating pulse. Formed by the synchronizer 13 along the falling edge of the strobe control reset impulse of the counter 7 (Fig. 3, plot 35) is simultaneously applied to the second input of the driver 14 (Fig, 3, plot 31a). The control pulses for rewriting information from the output of the counter 7 pulses into the register 15 and from the latter into the microcomputer 16 in the absence of a differential signal from the converter 2 by the synchronizer 13 are not generated (Fig. 3, plots 34a and Zba).

In the microcomputer 16, the incoming measurement results are accumulated in a series, which are statistically processed. For each of the series of measurements, the average value of the time of the nodal point in the counting pulses is found. This average value with the use of a graded characteristic stored in the microcomputer 6 is converted into units of the monitored parameter and presented on the light display of the digital indicator 8.

Claims (1)

Apparatus for pulsed eddy current monitoring comprising a pulse generator, an input connected to it a eddy current converter, a subtracting unit connected to the outputs of the eddy current converter, and an amplifier input connected to the output of the subtracting unit, serially connected clock generator, a matching circuit and a pulse counter and an indicator, characterized in that, in order to increase the reliability of the control by reducing the influence of the gap variation in a wide range, the specific electrical conductivity of the material, it is equipped with a serially-connected memory unit, a digital-to-analog converter, a comparator, and a useful signal extraction circuit, sequentially connected by a synchronizer and a pulse shaper, the output of which is connected to the second input of the coincidence circuit, and serially connected by a register and microcomputer whose output is connected with an indicator, the amplifier output is connected to the second input of the comparator, the output and the second input of the useful signal extraction circuit are connected respectively, the first input and the second output of the synchronizer, the first and second outputs of the pulse sensor are connected respectively to the first input of the register and the input of the memory unit, the second output of the pulse generator is connected to the second input of the synchronizer, the third output of the synchronizer is connected to the second input of the pulse counter, the fourth output the synchronizer is connected to the second input of the pulse generator, the fifth output of the synchronizer is connected to the second input of the register, and the sixth output of the synchronizer is connected to the second input of the microcomputer . GB