EDDY-CURRENT MEASURING DEVICE Russian patent published in 1995 - IPC

FIELD: instrumentation. SUBSTANCE: eddy-current measuring device has generator 1 of rectangular pulses with control by frequency, power amplifier 2, eddy-current converter 3, synchronous detector 4 and differential amplifier 5 connected in series. Eddy-current converter includes measurement and compensation inductance coils 6,7 and test inductance coil 8 connected differentially, the latter being inductively coupled with compensation coil 7. Leads of test coil 8 are interconnected through controlling key 9 which controlling input is linked through flip-flop 10 to output of generator 1. Amplifier 2 is built on key version and incorporates source 11 of constant voltage, two controlling keys 12, 13 and two resistors 14, 15 coupled to coils 6, 7 of eddy-current converter 3 in compliance with bridge circuit. Controlling inputs of keys 12 and 13 are connected to counterphase outputs of generator. Device is also fitted with differential amplifier 16, subtracter 17 and three reservoir capacitors 18-20. Synchronous detector 4 is produced on base of four-channel commutator 21 which first and second outputs are connected to common wire through capacitors 18, 19 and to inputs of differential amplifier 5. Third output of commutator 21 is not used and fourth one is connected to common wire through capacitor 20. Reference voltage source 22 is linked to second input of subtracter 17. EFFECT: increased reliability of device with simultaneous reduction of mass and dimensions. 2 dwg