PURPOSE: To enable measurement of changes in the conductivity and dielectric constant of a substance to be measured in a non-contact manner by employing a sensor comprising an excitation electrode led from a high frequency oscillator and a receiving detection coil.

CONSTITUTION: An oscillator 4 having a dry battery 2 as power source is incorporated into an aluminum cylinder 3 with the diameter of about 40mm and connected to a disc-shaped electrode 7 0.5mm thick via a lead 5 from the oscillator 4. An excitation electrode 7 is set on an insulation plate 8 and a flat spiral detection coil 10 is stuck the back thereof while the coil 10 is separated from a sample to be measured so as not to contact it. In this manner, the measurement of voltage changes by switching operation of the frequency enables the measurement of relative changes in the conductivity and dielectric constant of the sample being measured thereby assuring the measurement of changes in the conductivity and dielectric constant of a substance being measured in a non- contact manner.