Abstract: A heating unit includes a bridge having an arm in which there is located a heating element, and a circuit for directing a sensing current through the heating element. The circuit of the present invention reduces the duty cycle of the sensing current, thus reducing the average sensing current and allowing the use of higher peak sensing currents. In one embodiment, a set of zener diodes determines the start and stop points of the sensing current pulses. In another embodiment, the start and stop points are determined by electronic logic performed by a quad comparator. In another embodiment, one of the zener diodes is replaced by a SIDAC. The invention allows sensing of heating elements having very small temperature coefficients. The circuits of the invention produce a sensing current which is relatively unaffected by variations in supply voltage.

Abstract: A heating unit includes a bridge having an arm in which there is located a heating element, and a circuit for directing a sensing current through the heating element. The circuit of the present invention reduces the duty cycle of the sensing current, thus reducing the average sensing current and allowing the use of higher peak sensing currents. In one embodiment, a set of zener diodes determines the start and stop points of the sensing current pulses. In another embodiment, the start and stop points are determined by electronic logic performed by a quad comparator. In another embodiment, one of the zener diodes is replaced by a SIDAC. The invention allows sensing of heating elements having very small temperature coefficients. The circuits of the invention produce a sensing current which is relatively unaffected by variations in supply voltage.

Abstract: The present invention is an image intensifier assembly that includes a Generation III image intensifier tube coupled to a single piece fiber optic inverter expander element. The single optical couple to the fiber optic expander element greatly enhances the overall performance parameters of the Gen III tube, as compared to traditional relay lens assemblies. The present invention image intensifier assembly can be directly substituted for a Generation II image intensifier tube assembly in a given application.