Also referred to as capacitance, this method relies on the relatively high dielectric of water.

Numerous techniques have been developed to determine dielectric, including radio frequency, microwave, and time domain reflectometry. In order to measure the relative dielectric of a material it is necessary to electrically couple the material to the sensing circuit. This may be done by placing the material between two parallel electrodes, but this does not lend itself readily to online application. If the sensing circuit operates at radio frequency, it is fairly simple to propagate RF energy through the material and thus couple to the product without physical contact. Planar fringe field electrodes provide a single-sided measurement structure less obstructive to the process.

The electrical analogy of a solid product is a capacitor in parallel with a leakage conductance. These components are both influenced by moisture, but whereas dielectric is related in a very predictable manner, the loss factor is not. The combined components represent a complex impedance which can be easily measured, but which may be influenced by variables other than just moisture.

True dielectric moisture instruments are rare, since most of the low cost instruments make no attempt to separate the dielectric and loss components. The lowest cost instruments make little or no attempt to even measure the combined impedance with any long-term stability and repeatability. The Sensortech Systems Dielectric Measurement Technique is refined to the extent where the two components are completely isolated and can be measured independently. The patented resonant frequency principle improves accuracy and repeatability.