| 摘要 |
The present invention relates to a programmable current or voltage sensing circuit for use in measuring concentration levels of combustible gases. Generally, the present invention provides an electrical apparatus for detecting the concentration level of a combustible gas comprising a pair of sensor elements each having an electrical output which is compared to the other for measuring the amount of the gas undergoing combustion. The apparatus also generally comprises a first pair of electrical circuits each connected to one sensor element for controlling the amount of electrical current or voltage at that element, a second electrical circuit connected to both elements for comparing the electrical outputs of the sensor elements to measure the amount of gas undergoing combustion, and a third electrical circuit having a reference output signal for individually controlling the amount of electrical current or voltage generated by each of the first electrical circuits. Preferably, the sensor elements are comprised of electrical resistors coated with a heat conducting material wherein one of the elements is further coated with a chemical substance for catalyzing combustion of the gas, such that the combustion will cause the resistance of the catalytically coated sensor element to increase relative to the resistance of the other sensor element.
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