SU828060A1 - Eddy current device for non-destructive testing - Google Patents

Description

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The invention relates to destructive testing and to be used for eddy current testing of electrically conducting objects.

Eddy current devices for non-destructive testing are known, comprising a series-connected generator, eddy current transducer, compensator, signal processing unit and display unit.

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A disadvantage of the known device is that it does not have the necessary endowment of control due to the presence of a change in the level of undercompensation in the course of its operation when the external conditions, such as temperature, vary.

Closest to the invention to the technical essence is an eddy current device for non-destructive testing, containing a series-connected generator, eddy current transducer, selective amplifier, phase-sensitive detector, the first input of which is connected to the output of the selective amplifier, and the second input is connected to the output of the generator, switch, first input which is connected to the output of the selective amplifier, two memory circuits, the first inputs of which are connected to the outputs of the switch, the differential Amplifier, the inputs of which are connected to the outputs of the memory circuits, the signal processing unit, the control and indication unit 2. This device does not provide the necessary reliability of control, as it does not have the ability to suppress the influence of the under-compensation level on the results of the control. The purpose of the invention is to increase the reliability of the control.

The goal is achieved due to the fact that the device is equipped with two gated blocks, connected by the first inputs to the generator, the second inputs to the output of the selective amplifier, the third inputs to the output of the control and display unit, the first outputs to the first input of the switch and the second outputs to the control the inputs of the switch and the inputs of both memory circuits. The gating unit may consist of a phase-shifting circuit, the input of which is connected to the output of the selective amplifier, a switch, the first input

The first group of contacts is connected to the output of the phase-shifting circuit, and the second input is to the generator, the first input of the second group of switch contacts is connected to the output of the selective amplifier, and the output to the first input of the switch, a comparator connected by its inputs to the output of the first group of switch contacts, and output - to the input of a frequency divider with an adjustable division coefficient, the output of which is connected to the first input of the synchronization circuit, connected by its second input to the output of the control unit and indication and, with its output, with the control inputs of the switch and the memory circuit.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 is a block diagram of the gating unit.

The eddy current nondestructive testing device contains a series-connected generator 1, an eddy current converter 2, a selective amplifier 3, a phase-sensitive detector 4, the first input of which is connected to the output of the selective amplifier 3, and the second input is connected to the output of the generator 1, the switch 5, the first and second circuits 6, 7 memories, the first inputs of which are respectively connected to the first and second outputs of the switch 5, differential amplifier 8, whose inputs are connected to the outputs of the memory circuits 6, 7, processing unit 9 signals, control and indication unit 10, first and second blocks 11 and 12 are gated, and for the first time their inputs are connected to the output of generator 1, the second inputs are connected to the output of selective amplifier 3, the third inputs are respectively connected to the first and second outputs of control and display unit 10 . The first outputs are connected to the first input of the switch 5, the second output of the gating unit 11 is connected with the second inputs of the switch 5 and the memory circuit 6, and the second output of the gating unit 12 is connected to the third input of the switch 5 and the second input of the memory circuit 7.

Each gating unit contains a phase-sensitive circuit 13 with a phase shift of 90 °, connected to the output of the selective amplifier 3, a switch 14, the first input of which is connected to the output of the generator 1, the second input is connected to the output of the selective amplifier 3, the third input is connected to the output of the phase-sensitive circuit 13 , the first output is connected to the first input of the switch 5, and the second output is connected to the input of the comparator 15, which registers the input voltage zero transitions, the frequency divider 16 with an adjustable division factor to, the input of which is connected to the output of the comparator 15, a synchronization circuit, based on D-triggers 17, 18, and a conjunction circuit 19 (double-buffered synchronizer), the clock input of which (trigger 17) is connected to the output of divider 16, preset input (trigger 18 ) is connected to the output of the control and display unit 10, and the output to the control inputs of the switch 5 and the memory circuit 6 (7). The device works as follows. Generator 1 with a siiusoidal current. It excites converter 2, which interacts with the control object (not shown). The output signal of the Converter is fed to the input of the selective amplifier 3, amplifying the first harmonic signal,

II is detected by a phase-sensitive detector 4. The high-frequency oscillation envelopes the PA input of the switch 5. The switch channel is selected by the signal of the control unit 10 and indicacin. In the compensation mode, the signal arrives from the first output of control unit 10 and 1I1 and the input of gating unit 11 generates a strobe regular pulse, the duration of which is a multiple of the first period of the generator 1 voltage, and the fronts coincide with the moments of maximum of the first harmonic. The P1 pulse of the gate enters the second input of the switch 5 and the second input of the memory circuit 6 and permits the passage of voltage from the output of the selective amplifier 3 to the first input of the circuit 6, remember the memory. The strobe pulse decays and the UnK- compass voltage is remembered. In the measurement mode, the input of the gating unit 12 receives a signal from the second output of the control and display unit 10, through which the gating unit 12 produces a pulse of the strobe (apalogchnio previous) allowing the voltage to pass through the second channel of the switch 5 and the first input of the supply circuit 7. At the time of the termination of the pulse, the voltage is remembered,

equal amount of information voltage UH and UjiK. At the output of the differential amplifier 8, a voltage appears, directly proportional to U, which enters the signal processing unit 9 and, after processing, is indicated by an indication by the control and indication unit 10.

The control and display unit 10 may be a manual control keypad with analog or digital display and / or a controller software programmer, made, for example, on the base of a microprocessor system.

Depending on the features of the control process, there are two possible ways to connect the gating units. If the informative factor of the non-destructive control is the amplitude of the signals of the eddy-current transducer 2, and compensation and measurement are carried out in the interaction

with the control object, the processing is performed at a high frequency. The detector 4 can be turned off and the output of the selective amplifier 3 is directly connected to the input of the switch 5. Shifts of the initial phases of the undercompensation voltages

and the useful signal relative to the voltage of the generator 1 are equal, i.e., fo r g:: o- In general, pho is a variable value depending on the external conditions and characteristics of the control object, for example, temperature, electrical conductivity, etc. As a reference signal, to synchronize the t / HK and ZK memorization points (Un + UHK, you must use the first signal harmonic. To implement this switching on option, switch 14 (FIG. 2) connects the output of the selective amplifier 3 via closed contacts a, c and b, d with the first entrance m switch output 5 and the phase-shifting circuits 13 - to the input of a threshold device 15. The detector 5 wherein the operation of the device does not affect.

If compensation is to be carried out without a control object, such as with thickness, then the initial phases of the useful signal pho (when interacting with the control object) and the voltage of under-compensation are not equal to each other, and the phase shift between them is variable, depending on external conditions. In addition, often with non-destructive testing, the phase of the eddy-current converter signals serves as an informative factor. Therefore, the processing needs to be done but the envelope of the high-frequency signals of the eddy current transducer after synchronous or phase detection. Synchronization of memorization points is also necessary here, since periodic eddies, such as crosstalk, with multi-frequency monitoring, often act on the eddy current transducer and measuring path. If the stresses are memorized at times that are multiples of the interference period, then its effect on the result is significantly reduced. To do this, the generator strut 1 can be used as the reference signal of the gating blocks, from which a straight strobe pulse is formed, whose duration (by setting the appropriate division factor k) is a multiple of the interference voltage period. For this purpose, the switch 14 closes the contacts c and d, and the contacts a, c and b, d opens.

Claims (2)

1. Eddy current device for a destructive control, containing a series-connected generator, eddy current transducer, selective amplifier, phase-sensitive detector, the first input of which is connected to the output of the selective amplifier, and the second input is connected to the output of the generator, the switch, the first input of which is connected to the output of the selective amplifier, two memory circuits, the first inputs of which are connected to the switch outputs, a differential amplifier whose inputs are connected to the outputs of the memory circuits a signal block, a control and indication unit, characterized in that, with the purpose of improving the reliability of control, it is equipped with two gating units connected by the first inputs to the generator, the second inputs to the output of the selective amplifier, the third inputs to the output of the control unit and indication, the first outputs to the first input of the switch and the second outputs to the control the inputs of the switch and the inputs of both memory circuits. 2. The device according to claim 1, characterized in that the gating unit consists of a phase-shifting circuit, the input of which is connected to the output of the selective amplifier, switch, and the first input of the first group the contacts of which are connected to the output of the phase-shifting circuit, and the second input to the generator, the first input of the second group of contacts of the switch is connected to the output of the selective amplifier, and the output to the first input of the switch, the comparator connected by its inputs to the output of the first group of switch contacts, and its output to the input of a frequency divider with an adjustable division factor, the output of which is connected to the first input of the synchronization circuit connected by its second input to the output of the control and display unit, and its output — with the control inputs of the switch and memory schemes. Sources of information taken in attentive examination 1. Instruments for non-destructive control of materials and products. Directory. Ed. V. V. Klyuev. Prince 2, M., “Maschinostroenie, 1976, p. 2. USSR author's certificate No. 564589, cl. G 01N 27/86, 1975 (prototies).