Multiple-frequency permittivity tester

An electrical testing system having an output that is a function of the permittivity of materials for determining qualities of the materials, comprising:

• generating means for exciting periodic electrical waves at a plurality of frequencies, said generating means having signal selective circuits for supplying said waves at respective predetermined ones of said frequencies, a capacitive cell to receive materials for testing, the capacitive impedance of said cell being dependent on the complex permittivity of material placed therein, said signal selective circuits of said generating means connected to said capacitive cell to apply thereto said periodic electrical waves at said predetermined frequencies, output selective circuits connected to said capacitive cell for receiving voltages developed thereacross, said output selective circuits having different output circuits responsive to application of voltages at different ones of said predetermined frequencies for developing different output voltages therein in response to application thereto of said voltages developed across said capacitive cell, the magnitudes of said different output voltages varying systematically in accordance with different impedances of said cell at different ones of said predetermined frequencies, computing means connected to said output circuits of said output selective circuits, said output circuits applying said different output voltages to said computing means, and said computing means being programmed to provide in response to application thereto of said different output voltages an output indicative of the amount of a particular quality associated with the material being tested.