Abstract: A method and apparatus for detecting the end point of a plasma etching process comprising the use of an optical technique in which light is beamed on the layer to be etched and the resulting beam that is reflected and refracted is detected. Sharply different values of light intensity can be detected when the desired layer is etched and the next layer receives the light beam. A laser is preferably used to obtain an intense and substantially uniform frequency light source.

Abstract: A strain gauge element having an elastic beam with field effect transistors deposited on one surface arranged in a Wheatstone bridge so that deformation of the beam produces a proportional imbalance signal across the bridge, and means for applying a gate biasing voltage to the transistors with at least one such voltage being adjustable so that the bridge can be electrically balanced for a null or no load condition.

Abstract: A chart recorder writing pen of the kind in which the oscillating shaft of a motor drives an arm in a plane perpendicular to the shaft through a linkage causing the writing tip of the arm to move in a straight line; the writing device of the pen being an ink jet supplied with ink through a substantially rigid conduit having substantial portions on opposite sides of the axis of the shaft and being journaled on an axis colinear with the motor shaft axis.

Abstract: A sensor developing a digital output in response to force induced deflection in which the deflection is of a beam formed to have, under stress, a surface undulate in both compression and tension. The signal is developed from piezoelectric transducers connected in a pair of oscillator circuits utilizing surface acoustic wave paths through, respectively, the tension and the compression portions of the beam surface. The frequencies of the oscillators are compared and the frequency difference resulting from beam deflection is sent as a signal to a counter to give a digital read out of the force causing the deflection. The beam is formed of steel and the piezoelectric surface for the surface waves and the interdigitated conductors forming the transducers are deposited by thin film techniques on the beam.