SU1569527A1 - Eddy current device for nondestructive inspection of conductive articles - Google Patents

Abstract

The invention relates to non-destructive testing and can be used to control the specific electrical conductivity and thickness of non-ferromagnetic metals. The aim of the invention is to expand the range of the tune away from changes in the gap and increase the accuracy of measurements. The device additionally includes N measuring channels, each of which contains an adder 8, a phase shifter 9 and a shaper 10. In each additional measuring channel, the output voltage is summed with the output voltage of the converter 2 so that the maximum phase of the output voltage of the adders 8 is in the middle of one of N subranges. Phase shifters 9 equalize the maximum phase difference values in all channels. Through the exclusive OR 11 circuits, the OR 12 circuit, and the interval to code converter 13, a larger phase difference between the reference voltage and the output voltage of the measuring channel, i.e. automatically extending the range of detuning from the gap between the transducer 2 and the product being monitored. And the time interval to code converter 13, together with the digital indicator 5, makes it possible to increase the measurement accuracy. 2 Il.

Description

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The actuator 10. In each additional measuring channel, the output voltage is summed with the output voltage of the converter 2 so that the maximum phase of the output voltage of the adders 8 is in the middle of one of the π subranges. Phase shifters 9 equalize the maximum phase difference values in all channels. Through the schemes EXCLUSIVE OR 11, the scheme OR 12 and transform

The invention relates to non-destructive testing; in particular, to control the specific conductivity and thickness of non-ferromagnetic metals.

The aim of the invention is to expand the range of the tune away from changes in the gap and increase the accuracy of measurements.

FIG. 1 shows a block diagram of the device proposed, FIG. 2 - dependence of the indicator readings on the gap between the transducer and the product under test.

The device contains a series-connected generator 1, a converter 2 and a measuring channel (not shown), including an amplifier 3 connected to the converter 2 and a phase detector 4 and a series 5 connected in series, as well as a reference channel 6, a driver 7 connected between the output of the amplifier 3 and the input The base detector 4, n additional measuring channels (not shown), each of which consists of a series-connected adder 8, a phase shifter 9 and a former 10, the first inputs of the adders 8 are connected to the output of amplifier 3, and the second to the output of converter 2, phase detector 4 is made in the form (n -I- 1) EXCLUSIVE OR 11 circuits, the first inputs connected to the outputs of drivers 10, the second input of the first circuit EXCLUSIVE OR 11 is connected to the output of the reference channel 6, and the second inputs of each of the following circuits EXCLUSIVE OR 11 - to the output of the formers 7 and 10 of the previous measuring channel, the circuit OR 12 connected by inputs to the outputs of the circuits EXCLUSIVE OR 11, the converter

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L 13 interval in the code allocates a larger value of the phase difference between the reference voltage and the output voltage of the measuring channel, i.e. automatically extending the range of detuning from the gap between the transducer 2 and the product being monitored. And the time interval to code converter 13, together with the digital indicator 5, makes it possible to increase the measurement accuracy. 2 Il.

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13 time interval in the code connected by the input to the output of the circuit OR 12, and the output - to the indicator 5, while the amplifier 3 is made selective.

The device works as follows.

The voltage from the generator 1 is fed to the exciting winding (not shown) of the converter 2. The voltage from the oppositely connected measuring and compensation windings (not shown) through the selective amplifier 3 and the rectangular voltage driver 7 is fed to the first input of the phase detector 4. The measuring. and the compensation winding of the converter 2 is located on the same axis symmetrically with respect to the exciting winding. The input of the reference channel 6 receives the voltage from the compensation winding remote from the controlled product for a longer distance. From the output of channel 6, the rectangular voltage is applied to the reference input of the detector 4.

To create the extremality of the dependence of the phase of the output voltage of the converter 2, the UK voltage of the compensation winding is chosen greater than the initial voltage U0 of the measuring winding. The magnitude of the initial unbalance of the transducer 2 is chosen such that the phase extremum is near the upper limit of the gap ranges between the transducer 2 and the product under test.

The entire range of variation of the gap is divided into equal subranges. The number of measuring channels (including the main one) is equal to the number of subbands. In additional measuring channels, the magnitude of the additional voltage,

arriving at the inputs of the adders 8 from the output of the converter 2, is chosen such that the maximum of the phase of the output voltages of the adders 8 is in the middle of the corresponding subrange of the gap change. Phase shifters 9 equalize the maximum values of the phase difference of the output voltages of all measuring channels relative to the reference voltage of channel 6. Shapers 7 and 10 convert sinusoidal voltages into rectangular, arriving at the inputs of the EXCLUSIVE OR circuit 11. At the output of the first circuit 11, rectangular pulses are generated, the duration of which depends on the phase difference between the output voltages of the driver 7 and the reference channel 6. In one period, two pulses are generated along the front and. rear fronts of rectangular stresses. This makes it possible to reduce the influence of the change in the amplitude of the output voltage of the converter 2 on the accuracy of the phase measurement.

At the output of each of the following EXCLUSIVE OR 11 circuits, the duration of rectangular pulses depends on the difference between az c between the output voltages of the subsequent and previous measuring channels, while if the phase difference is negative, the output of the OR 12 circuit increases the duration of the output pulses phase difference. With a positive phase difference, the duration of the output pulses of the OR 12 circuit remains the same, depending on the previous measurement channels.

At the output of the OR 12 circuit, at any gap, square-wave pulses are formed with a maximum duration corresponding to the parameter being measured. The interval Converter 13 in the code converts the duration of the pulses into a parallel code supplied to the digital indicator 5.

The number of measuring channels depends on the accuracy of the measurement and the range of variation of the gap. Doubling the number of measuring channels allows the gap range to be doubled at the same accuracy.

FIG. 2 shows the experimentally obtained dependences of the readings of the thickness gauge of alloyed drill pipes on the gap. The dotted line shows the dependence of the same

thickness gauge and gaiter - with

three additional measuring channels. The radius of the exciting winding of the ECP is R. 17 mm, and the measuring radius is 14 mm. The diameter of the test tubes is 147 mm, the specific conductivity is 20 MSn. The construction of a thickness gauge according to the proposed scheme with three additional measuring channels makes it possible to measure the wall thickness of the pipes with an accuracy of J 1% when the gap changes from 2 to 15 mm and the conductivity is constant.

The proposed device allows a several-fold increase in the range of clearance from the gap and can be used to measure the specific conductivity and thickness of non-ferromagnetic metals.

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Claims (1)

Invention Formula An eddy current device for non-destructive testing of electrically conductive products, containing a series-connected generator, a transducer, and a measuring channel, including an amplifier connected to the transducer and a series-connected phase detector and indicator, as well as a reference channel, characterized in that changes in clearance and improved measurement accuracy 5 it is equipped with a driver connected between the amplifier output and the input of the phase detector, additional measuring channels, each of which consists of successively 0 connected adders, a phase shifter and a former, the first inputs of the adders are connected to the output of the amplifier, and the second to the output of the converter, the phase detector is designed as 5 n + 1 EXCLUSIVE OR circuits, the first inputs connected to the shaper outputs, the second input of the first EXCLUSIVE OR circuit is connected to the output of the reference channel, and the second inputs of each of the subsequent EXCLUSIVE OR circuits - to the output of the former measuring channel, OR circuit connected by the inputs with the outputs of the EXCLUSIVE OR circuits, the conversion of the time interval into the code connected by the input to the output of the OR circuit, and the output to the indicator, and the amplifier is made selective. U, 0 t, mm 0.5 V / 5 2 tf "2hlRB V