ELECTROMAGNETIC THICKNESS GAUGE Russian patent published in 1996 - IPC

FIELD: nondestructive testing. SUBSTANCE: invention refers to nondestructive eddy-current method of testing, specifically to measurement of thickness of dielectric coatings on conductive nonmagnetic base. Electromagnetic thickness gauge has self-excited oscillator, emitter follower, measurement circuit with eddy current converter, constant current amplifier, indicator. It is fitted with reference voltage circuit manufactured in the form of diode and resistor connected in series and placed between output of emitter follower and input of constant current amplifier which is built on balance circuit. Second diode and indicator connected in series are inserted into output diagonal of amplifier. Eddy current converter is manufactured in the form of rod ferrite core and magnetized shell located close to its working butt. Optimum dimensions of converter are chosen from relations l_fz/h_w≈ 18÷20,; d_w/d_fz≈4,5÷5,; where l_fz is length of ferrite rod; h_w is height of application of winding; d_w is medium diameter of winding; d_fz is diameter of ferrite rod. EFFECT: increased precision due to tuning away from effects of charges of electric conductivity of metal nonmagnetic base. 2 dwg