SU862063A1 - Method and device for measuring resistance of thin conductive coatings - Google Patents

Description

(54) A METHOD FOR MEASURING THE RESISTANCE OF THIN CONDUCTING COATINGS AND A DEVICE FOR HIM The invention fires to non-destructive testing and can be used for non-destructive testing of a coating applied to a non-conductive substrate. A known method of controlling the resistance and thickness of the conductive films and the device for its realization. The essence of the method is that eddy currents are induced by an eddy current transducer in the film, while simultaneously measuring the gap between the product and the current transducer by means of a capacitive transducer, they are removed and summed algebraically: the transducer signals and the measured parameter U. The disadvantage of this method is its dependence on the influence of the gap, which is explained by the nonlinear characteristic of the capacitive transducer. IMPLEMENTATION The closest to the technical essence of the present invention is a device that implements a method of measuring the resistance of race conducting coatings based on the use of two eddy current parametric, inductively coupled transducers powered by a single generator, which means that the transducers are placed above the measured coating , the magnitude of the differential signal of the converters is determined, and the value of the measured resistance is judged from it. A device for implementing the method comprises a series-connected generator, a four-shouldered measuring bridge, on the adjacent arms of which are included progressively resonant circuits, each of a eddy current transducer and condensate, an amplifier, an amplitude detector and an indicator. The disadvantage of the known method is the moisture dependent L. measured parameter og value.

The aim of the invention is to limit the influence of the size of the gap on the measured parameter,

The goal is achieved by installing transducers over a sample with a coating M having the smallest resistance value from a predetermined range, measuring the reactive impedance component of each preophaser, changing the frequency of the supply generator, while for each of the transducers the difference between the measured value and the value of the reactive component of the impedance of the unloaded transducer will not be 1-3%, set the transducer over the measured coating, determine 1 The magnitudes of the transducer signals, the projection components of the active input co-properties, depending on the influence of the coating, and determine the magnitude of the difference signal. In the device, the goal is achieved by the fact that the two other adjacent terminals of the device are made in the form of two standard capacitors, and the resonators circuits are variable, the transducers are located at the same direction, kx radii have a ratio of 1: 4, and the magnitude of exemplary capacitors is chosen from the ratio

-)with

.CS4M44

2

where a is the radius of the larger converter; Rd - radix smaller converter;

fj is the number of turns of the converter of a larger radius; W is the number of turns of the transducer of a smaller radius; Co - exemplary capacitor of the opposite type of k) ilech}

Sz - ofaztsovy condensate opposite shoulder Converter,

The drawing shows a block diagram of a device implementing the present method. The device contains a series-connected generator 1, a four-meter measuring bridge 2, an amplitude detector 3, an amplifier 4 and an indicator 5, Bridge 2 is made in the form of two sequences X of the resistive circuits from the first (C / J) variable capacitor 6 and the first eddy current converter 7, second (04) variable capacitor

8, vsrc th eddy current transducer

9 included in the adjacent shoulders of the bridge, in series with the converter 9 MCW, the adjusted resistor is turned on

10, Paremetra converter 7: radiusC, number of turns -W. . Transducer parameters 9: radius - szd. / number of turns W4. . The two adjacent arms of bridge 2 are made in the form of exemplary cabinets 11 and 12 (Cj and Cj); capacitor 11 (Cj) is opposite the shoulder with converter 9, and capacitor 12 (C is the shoulder with converter 7, Equal condensation points 6.8

and 11.12 are the power diagonal and connected to the output of the generator 1, the common points of the sensor 11, the converter 7 and the capacitor 12, the converter 9 are the measuring diagonal and connected to the input of the detector 3,

The transducer coil radius 7 is four times the transducer radius 9,

The device works as follows.

Claims (2)

The signal from generator 1 is fed to the diagonal power supply of bridge 2, the unbalance voltage of bridge 2 with a measurement diagonal is fed to the input of detector 3, where it is detected and fed to amplifier 4, indicator 5 connected to the output of amplifier 4, records the value of the output voltage. The initial frequency of the generator 1 is set based on the resonant parameters of circuits 6.7 and 8.9. With the aid of capacitors 6 and 8, the shoulders of bridge 2 are adjusted to resonance (with non-loaded pre-phonazovels 7, 9). With balance, the bridge 2 is balanced by zero indications on iDicagora 5; Note the value of the capacitance of the condensate 6; On the transducer 7, install samples of the coating OZ range O range. When capacitor 6 is in resistor 10, bridge 2 is balanced for each sample, the value of condenser is 6 n of the cutter 10, the frequency of re & amparpa 1 is changed, followed by the maximum difference between the extreme values of x 6 capacitor for each of samples from the specified diaoassic were no higher than 3–4%. The frequency is changed until the maximum value of the change, the value of resistor Y, is reached, which ensures maximum clearance from the gap for this range of coatings. The frequency set in this way will be the operating frequency of the generator 1. Then the former 9 is concentrically fixed inside the core 7 at the same distance from the measured coating (working field). The value of the capacitor 11 is chosen, and the ratio of the capacitors 11, 12 in modulus should be much greater than the resistance modules of the tuned resonant circuits. After setting the parameters of the capacitors 11, 12 and adjusting the bridge, the converters 7, 9, mounted concentrically, bring the sample from the hopper. eat. When adjusting the bridge on the scale of indicator 5 to zero in the absence of a sample, the readings on the scale of indicator 5 will be directly proportional to the conductivity of the square of the surface of the coating being measured or inversely proportional to its resistance. The advantage of this method is the possibility of detuning from the gap when it changes significantly. x and Obtaining a linear dependence of the output voltage variation on the change in the conductivity of the coating being measured. 1. Method for measuring resistive conductive coatings based on the use of two eddy current parametric, inductively coupled transducers powered from a single generator, aa that the transducers are placed above the measured coating, determine the magnitude of the difference signal transducers and it is judged on the magnitude of the measured resistance, characterized in that, in order to detuning from the influence of the size of the gap on the measured parameter, transducers are set over the sample with the coating having the smallest resistance value from the specified range, the reactive impedance component of each pre-phase generator is measured, the frequency of the thawing generator is changed until for each of the converters the difference between the measured value and the value of the reactive impedance component of the non-flexible transducer will not be 1-3%, install the transducers over the measured coating, determine the values of the transducer signals, proportional to the components m active insertion resistances, depending on the effect of the coating, and determine the magnitude of the difference signal. 2. A device for implementing the method of claim 1, comprising a series-connected generator, a four-shouldered measuring bridge, the adjacent arms of which include series-resonant X-ray tours, each of a vortex-converter and a capacitor, an amplifier, an amplitude Detector and an indicator, characterized in that other adjacent shoulders of the bridge are made in the form of two exemplary capacitors, and the capacitors of the resonant circuits are variable, the converters are mounted concentric, their radii have a 1: 4 ratio, and Other model capacitors are selected from the relation where C (is the radius of the larger converter; Q is the pafljiyc of the smaller converter; W is the number of turns of the converter of a larger radius} C. Z. is the number of turns of the converter of a smaller radius | shoulder; Ca-oxidizer of opposite shoulder a-iW converter Sources of information taken into account during examination 1.US Patent Ms 30778S8, cl. 118-7, 1958, 2. Avtorskoe: certificate of the USSR 246868, kl.v O1 In 7/02, 1967 (prototype).