Combustible gas detector and method for its operation
AssigneeIndustrial Scientific Corporation
InventorsP. Richard Warburton, Chuan-Bao Wang
Life of this patent
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Abstract
A catalytic bead sensor or a semiconductor sensor is operated in a manner in which the power requirement is greatly reduced. The reduction in power is accomplished by operating the sensor at a temperature less than the desired operating temperature in the absence of a combustible gas and increasing to the desired operating temperature when the sensor is exposed to a combustible gas.
Claims24
A method for operating an instrument for detecting a combustible gas comprising a sensor including a heated surface on which the combustible gas reacts to cause a variation in an electrical parameter output, an electrical power supply for the instrument including a connection for heating the heated surface, a measuring unit for measuring gas concentration based on readings from the sensor and an output display for indicating the presence of a combustible gas, comprising the steps of:
- providing means for actuating the power supply based on the electrical parameter measured by the measuring unit;
- determining a first operating temperature T2 for the heated surface at which reaction of all types of combustible gas including methane takes place;
- in the absence of a combustible gas, operating the instrument with the heated surface at a second operating temperature T1 at which combustible gas reacts on the heated surface and which is less than T2;
- and
- determining, with the measuring unit, changes in the electrical parameter output of the sensor, and further supplying power to the sensor such that:
- when the sensor output is less than a predetermined threshold value, continuing to operate the sensor at temperature T1, and
- when the sensor output is at least equal to the threshold value indicating the presence of a combustible gas, increasing the temperature of the heated surface to T2, and operating at T2 during any time period when the electrical parameter is above the threshold value.
In an apparatus for detecting a combustible gas comprising a sensor including a surface heated to a predetermined temperature on which the combustible gas reacts to cause a variation in an electrical parameter output, an electrical power supply for the instrument including a connection for heating the heated surface, a measuring unit for measuring gas concentration based on readings from the sensor and an output display for indicating the presence of a combustible gas,
- the improvement comprising an actuating unit for controlling the power supply and a feedback link between the measuring unit and the actuating unit to provide gas concentration information to the actuating unit,
- wherein the actuating unit comprises means for heating the heated surface to a first temperature T1 at which combustible gas reacts on the heated surface, when combustible gas is detected at less than a predetermined concentration by the measuring unit, and heating the heated surface to a second temperature T2 which is greater than T1 when combustible gas is detected at or above the predetermined concentration.
Dependencies are inferred from the claim text.