METHOD FOR MEASURING OF ALTERATION OF SURFACE POTENTIAL Russian patent published in 2000 - IPC

FIELD: electric instruments. SUBSTANCE: modified Kelvin method for measuring contact difference of potentials provides possibility to observe alteration of surface electrostatic potential of metal or semiconductor on oscilloscope screen. Goal of invention is achieved by simultaneous application of direct voltage and sine-shaped modulation voltage to plates of dynamic capacitor, which is formed by tested sample and vibrating reference electrode. AM signal, which is excited in capacitor circuit is amplified and applied to Y-input of oscilloscope, which X-input receives voltage from modulation voltage generator. Screen of oscilloscope displays AM signal, which envelopes represent two intersecting straight lines. Movement of intersection point of envelopes describe alteration of surface potential. Potential alteration value ΔV conforms to equation ΔV = U_mX/X_m, where U_v is modulation voltage amplitude, X is alteration of coordinate of intersection point of envelopes, when surface potential variation is ΔV, X_m is maximal deviation of beam with respect to horizontal line. EFFECT: increased precision. 5 dwg