Abstract: RF energy provided by electrodes positioned between a product is used to heat a product that exhibits a variable impedance during the heating process. As the product's impedance changes during the heating process, RF heating system impedance can be maintained constant by adjusting the distance between the electrodes, adjusting the impedance of a variable impedance device connected between the RF power source and an electrode, or a combination of electrode distance adjustment and impedance adjustment of the variable impedance device. The system is particularly applicable to the heating or pasteurization of bulk food products with multiple heating zones.

Abstract: An RF plasma power monitor that monitor voltage, current and DC bias adjacent the plasma load and processes the sensed data in a digital data processor to provide true power at the load. Provision is also made for the control of an RF power source to maintain power at the load at a preset level irrespective on impedance fluctuations and reflections.