Importance

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Abstract

This invention discloses a method and apparatus for accurately measuring and controlling the amount of power being absorbed by a load within the irradiating region of a diathermy applicator head. A desired power setting is initially preset into the diathermy apparatus. Thereafter, the diathermy apparatus is keyed on for a predetermined duty cycle causing RF energy to be generated within the applicator head during this time period. The level of power being absorbed by the load is then ascertained by measuring voltage and current flow in the head during the duty cycle. In the preferred embodiment of the invention, the electrostatic energy generated in the applicator head is attenuated by an electrostatic shield. Attenuation of the electrostatic energy improves the stability of the diathermy apparatus by significantly reducing electrostatic coupling between the applicator head and its attendant load. Once the electrostatic field is eliminated, the level of power being applied to the applicator head accurately represents the level of power being absorbed by the load within the irradiating region of the head. The diathermy apparatus is also provided with circuitry for keeping the applicator head in electrical resonance thereby improving the power measurement by ensuring that the voltage and current are locked in phase. The measured level of power is then multiplied by the duration of the duty cycle to provide a figure representative of the total amount of power being absorbed by the load. This figure is compared with the preset level and the duty cycle is adjusted accordingly.

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First Claim