Abstract: A position sensing device having an insulating board, a first conductive sensing element, a second conductive sensing element, an oscillator, conductive material, a differential amplifier, and a processor. The first and second spaced conductive sensing elements are on the insulating board. The oscillator generates an oscillating signals and the conductive material is spaced from the sensing elements. The conductive material receives the oscillating signal to create an electric field between the conductive material and the first and second sensing elements. The differential amplifier includes differential inputs that are connected to the conductive sensing elements. The signal levels at the differential inputs vary based on the position of a pointing object of a user relative to the first and second conductive sensing elements. The processor generates a position signal based on an output of the differential amplifier.

Abstract: Method and apparatus for monitoring and maintaining the geometry of plasma in a plasma chamber is disclosed wherein the plasma density and plasma temperature in the chamber are monitored to calculate an initial sample dc voltage which is applied to the sample or first probe in or adjacent to the temperature. The current to the sample or first probe is then measured, a new sample voltage for the sample or first probe is then calculated and applied and these latter steps of measuring, calculating and applying are repeated. Different wire and flat probe structures and positions are disclosed.