Four Probe Conductivity

Four probe conductivity measurement gives the in-plane conductivity by the way of sheet resistance and in some cases, volumetric (bulk) resistivity of the samples. Difference in the sheet resistance of bare and coated samples, gives an estimate about the in-plane conductivity of the coating alone. Constant current is applied automatically, through two outer probes and the voltage developed with the other two probes is measured. The direction of the current flow can be reversed. The surface of the sample should be flat, for accurate measurements.