SU1323943A1 - Digital device for eddy-current check - Google Patents

Abstract

The invention relates to the field of non-destructive quality control of material and products and can be used in the aviation, engineering, metallurgical industries in a number of other areas of national economy. The aim of the invention is to improve the measurement accuracy by linearizing the output characteristic. The device contains an oscillator that feeds an eddy current transducer, the signal from which enters the information processing unit. Next, the linearization of the output characteristic uses an analog-to-digital converter, a fixed voltage block connected to the output of the information processing unit, a multiplexer unit whose analog inputs are connected to the outputs of a fixed voltage block, and the control inputs are connected to the high-end bits of the analog-digital converter. In addition, there is a digital-to-analog converter with information inputs connected to the outputs of the lower-order bits of the analog-to-digital converter and an analog input connected to one of the outputs of the multiplexer unit. An adder is connected to the output of the digital-to-analog converter, the other input of which is connected to the second output of the multiplexer unit. If a block of fixed voltages produces a set of constant voltages, then the output of the adder is connected directly to the digital indicator. To further improve the measurement accuracy by eliminating the effect of drifts in the DC circuits in a fixed voltage block, variable voltages of fixed amplitudes can be generated. In this case, an amplitude detector is turned on between the adder and the indicator. Thus, the device implements an on-line approximation of the output characteristic. 1 3. Clause f-ly. 2 Il. u (O with N3 CO with 4 CO

Description

This invention relates to a technique for non-destructive quality control of materials and products.

The aim of the invention is to improve the accuracy of control due to the linearization of the transfer characteristic.

logical input of DAC 5. Thus, depending on the code h of the lower bits of the A / D converter 4 at the output of DAC 5, the voltage varies linearly from 0 to i / ii / o 5 for the first section, to U, -U for the second section and t This voltage is supplied to one of the inputs of the adder 6, to the other input of which voltage is supplied from the output of the multiplexor unit 9, i.e. UQ for the first region, t / i for the second region, and so on. 1 shows the block diagram of the proposed digital device for eddy current testing, on

o4 P - - I

FIG. 2 is a graph explaining the operation of fU, as a result of the output of the adder, the device voltage b. Linearly depends on the size of the controller (Fig. 1) contains a sequential parameter. If block 8 is fixedly connected by an auto-oscillator 1, the rotating voltages are generated by a constant-current converter 2, and block 3 is the voltage, then at the output of the adder 6

information, ADC 4, D / A converter, 5, the sum will also be a constant voltage, which 6 and digital indicator 7, sequentially goes to the digital indicator 7. connected to each other, fixed voltage block 8 and multiplexer block 9, In block 8, the fixed-control inputs of which are connected to voltages of a constant voltage — to the older bits of the A / D converter 4; one of the outputs in the device may cause additional multiplexer unit 9 to be connected 20 additional error related to the temperature drift displacement audio in adder 6. For precision measurements in block 8 fixed voltage - it is possible to use an alternating voltage output of the adder 6 and the digital input. a fixed amplitude. At the same time, the indicator 7. completely excludes the influence of the temperature drift of the bias voltage of the operational amplifiers on the measurement accuracy. In this case, the output of the adder 5 includes an amplitude detector 10, a second input of the adder 6, and another output to the analog input of the DAC 5.

In addition, the device contains an amplitude detector 10 connected between the cyi output of the indicator

The device works as follows.

The oscillator 1 feeds the eddy current transducer 2, the signal from the output of which enters the information processing unit 3 1i. At the output of the latter, Q appears forming an alternating voltage of 6 V

the constant that is fed to the input of the digital indicator 7.

constant voltage, the value of which depends on the monitored parameter as shown, for example, in FIG. 2. This relationship is broken down into linear sections (Fig. 2). The number of such areas is determined by the required piecewise linear approximation. The voltage from the output of the processing unit 3 is fed to the input of the ADC 4, where it is converted into a binary parallel code. Block 8 of fixed voltages produces a set of constant or alternating voltages with a fixed amplitude, the value of which corresponds to the value of the monitored parameter at the nodal points (Uo, and ..., Uz) n lower-order bits

40

Claims (2)

1. A digital device for eddy current testing, containing a series-connected auto generator, an eddy current converter, and an information processing unit, as well as a digital indicator, characterized in that, in order to improve the control accuracy by means of linearization of the transfer characteristic, it additionally contains an analog-digital converter, multiplexer unit fixed voltages, digital-to-analog ADC 4 are connected to digital inputs, a digital converter and an adder, an input to a DAC 5, and the remaining high-level analog-digital converter is connected to the output of an information processing unit; the lower bits of the analog-to-digital converter output are connected to digital digital-to-analog inputs Dov - to the control inputs of the multiplexer unit 9, the outputs of which are switched depending on the code m of the high bits of the ADC 4 two voltages block 8 fixed voltages. At 50 converters, and the older ones - to the control if the code at the ADC output (), the first output of the multiplexer unit 9 will switch the voltage UQ, and the second - the voltage fy, -ОО, if () (2 -1 ), on the multiplexer unit inputs, the switched inputs of which are connected to the outputs of the fixed voltage block, and the outputs - with the analog input of the digital-to-analog converter and one of the first, the output will be switched to 55 from the inputs of the adder, the other input of which is U it is connected with the output of the digital-analogue preference -t / i, and so on. It supplies voltage from the output generator, and the output from the digital indipultiplexer unit 9 supplies it to an anchor. logical input of the DAC 5. Thus, depending on the code h of the lower bits of the A / D converter 4 at the output of the DAC 5, the voltage varies linearly from 0 to i / ii / o for the first section, to U, -U for the second section, and so on. This voltage is supplied to one of the inputs of the adder 6, to the other input of which voltage is supplied from the output of the multiplexer unit 9, i.e. UQ for the first section, t / i for the second section, etc. B - - I As a result, at the output of the adder, the voltage is linearly dependent on the value of 40 Invention Formula 1. A digital device for eddy current testing, containing a series-connected auto generator, an eddy current converter, and an information processing unit, as well as a digital indicator, characterized in that, in order to improve the control accuracy by means of linearization of the transfer characteristic, it additionally contains an analog-digital converter, multiplexer unit 2. The device according to claim 1, characterized in that it further comprises an amplitude detector, the input of which is connected to the output adder, and the output - to the digital display. 1 four() -ifyn. v // t - / Uo V, FIG. g Compiled by A. M gkov Editor A. LezhninaTehred I. VeresKorrektor V. But ha Order 2959/48 Circulation 776 Subscription VNIIPI USSR State Committee for Inventions and Discoveries 113035, Moscow, Zh-35, Raushsk nab. 4/5 Production and printing company, Uzhgorod, ul. Project, 4