EDDY-CURRENT INSTRUMENT FOR QUALITY CONTROL OF METAL ALLOYING Russian patent published in 1994 - IPC

FIELD: nondestructive eddy-current testing of complete alloy formation in mechanically alloyed powders. SUBSTANCE: quality control of mechanical alloying of metal powders is performed by eddy-current instrument containing eddy-current converter, self-excited oscillator and connected in series measuring unit, d. c. amplifier and indicator, due to the fact that it is provided with emitter follower with load in form of adjustable resistor and regulated capacitor. Eddy-current converter is of through-type. Measuring unit is four-arm bridge circuit, whose one arm is eddy-current converter with fixed resistor cut in series and second arm is capacitor. Two other arms form halves of transformer secondary winding cut in counter to each other. Instrument also includes connected in series transformer primary winding, second capacitor, diode and adjustable load resistor whose adjustable output is connected with d.c. amplifier input, second load is grounded and adjustable resistor, regulated capacitor and transformer primary winding form series oscillatory circuit whose Q-factor is lower than that of eddy-current converter. EFFECT: higher efficiency. 2 dwg