Abstract: A constant temperature catalytic gas detection instrument (10) has a gas sensor (14) whose operating temperature is maintained within a predetermined range by a novel control circuit. The gas sensor includes a reference element (16) and an active element (18) on which a metal oxide catalyst reacts with the combustible gas. First and second driver circuits (30 and 36) are provided for presenting operating voltages to the active element (18) and the reference element (16), respectively, of the gas sensor (14). The first driver (30) controls the power to the active element (18), to maintain its temperature within a predetermined operating range. The second driver (36) responds to changes in the power through the active element (18) with respect to the current through the active element (18), causing the current in the reference element (16) to track the current in the active element (18).

Abstract: A reference element for a catalytic gas sensor with improved life in the presence of combustible gases is described. The sensor comprises a filament such as a platinum-iridium alloy coated with a layer of titanium dioxide. The coating typically contains a high temperature stable inorganic binder such as aluminum oxide. The filament can be in coil-form pre-encased in a glass bead. Such sensor has long term stability in the presence of combustible organic gases such as alkenes, alkadienes, alkynes, and epoxide containing hydrocarbon gases, for example. Sensors containing such elements have particular utility in the area of mining and oil drilling environments, as well as industrial, safety, and commercial applications.

Abstract: The volumetric output of fuel injectors is rapidly and accurately measured y accumulating in first and second counters respectively, a count of pulses generated as a function of the strokes made by the injector, and a count of pulses generated by an optical encoder attached to the piston of a positive displacement flow meter through which the output of the injector is directed. When the first counter reaches a count representative of a preset number of injector strokes, the accumulated count in the second counter representative of injector output for the preset number of strokes is stored and displayed continuously while the counters are reset and the test cycle is automatically repeated. The direction of movement of the reciprocating piston of the positive displacement flow meter is automatically reversed by the control system as either end of travel is reached through coordinated operation of a pair of solenoid valves.