Electrodeless Measurement of Resistivities over a Very Wide Range

Abstract

Resistivity of electronic conductors, from metals to semi‐insulators, is determined from the change in grid current of a high frequency oscillator owing to the loading resulting from eddy currents in the sample. The signal appears as a pulse when the sample is dropped through the oscillator tank coil; greater amplification can be used than in previous eddy current methods where the sample was stationary during measurement; thus, higher resistivities can be measured. The samples can be sealed in ampoules and measured at high temperatures and pressures, limited only by the ampoule material. A typical calibration curve, made at 14 Mc and covering the range 10⁻⁶ Ω‐cm to 10⁸ Ω‐cm is given; application to the estimation of sample homogeneity is discussed.