Abstract: An improved apparatus for the "on-line" measurement of the dielectric constant or percent moisture of a material such as tobacco moving within the walls of a pipe or chute is disclosed. A differential capacitive technique is used for the measurement. The apparatus consists of a four electrode device, with two of the electrodes attached to the outside of the walls of the pipe or chute, and two of the electrodes attached to the inside of the walls of the pipe or chute. The two inner electrodes are connected by switches to the two outer electrodes, respectively, so that first and second capacitances appear at the output terminals of the electrode device depending upon the position of the switches. The output terminals of the electrode device are connected to an oscillator which produces an output signal indicative of the frequency of the oscillator's oscillation which is proportional to the capacitance at the terminals of the electrode device.

Abstract: An improved method and apparatus for determining the dielectric constant of materials which flow using capacitive techniques, having an electrode device with at least two output terminals and three or more electrodes spaced at fixed distances from one another. At least two of the electrodes are connected through a switch so that first and second capacitances appear at the output terminals of the electrode device depending upon the position of the switch. The output terminals of the electrode device being connected to an oscillator which produces an output signal indicative of the frequency of the oscillator's oscillation which is proportional to the capacitance at the terminals of the electrode device. The output signal of the oscillator is connected to a bi-directional counter or microprocessor which is used to calculate a value proportional to the change in capacitance of the electrode device when the switch is closed and to thereby determine the dielectric constant of a material being tested.