Abstract: An apparatus and method for sensing liquids, vapors and gases, which includes a conventional detection device operated in its non-linear region so that it is sensitive not only to substances having a Van der Waals' constant of greater than 9, but it is also sensitive to substances having a Van der Waals' constant of 9 or less. The device is driven by a constant current source, and a change in the level of the voltage across the detection device occurs upon exposure of the device to the substance being sensed. This voltage change is then detected to indicate the presence of the sensed substance. The relatively small voltage change associated with the detection device may be easily sensed by placing the detection device in a balanced bridge circuit. Further, the bridge circuit enables easy, accurate normalization of the apparatus in a reference environment. The non-linear characteristics of the detector allow it to be employed as a regulator for supplying a constant current to a power consuming device.

Abstract: An adsorbing type sensor of the type having electrically conductive adsorbent particles resiliently embedded in a surface and forming an electrical conductive path through the sensor, the resistance of which or in one embodiment current through which varies in response to the presence of an adsorbate medium exposed to the particles and in which the adsorbent particles are of varying sizes interspersed among one another and a method of increasing the sensitivity and range of an adsorbing type sensor by interspersing various sized abutting adsorbent particles.

Abstract: A sensing apparatus and method, for sensing liquids, vapors and gases, which includes a detection device constructed in accordance with the disclosures contained in U.S. Pat. No. 3,045,198, issued July 17, 1962, to Dolan et al. When the detection device is operated in a current saturated condition it becomes sensitive even to substances having a Van der Waals' "a" constant of nine or less. A change in the level of the current through the detection device occurs upon exposure of the device to the substance being sensed. This current level change is then detected to indicate the presence of the sensed substance. The relatively small current level change through the detection device may be easily discerned despite the fact that the base current is on the order of milliamperes by placing the detection device in a balanced bridge circuit. Further, the bridge circuit enables easy, accurate normalization of the apparatus in a reference environment.