| 摘要 |
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.
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