| 摘要 |
The present invention provides a monitor for detecting the presence of a combustible gas in an atmosphere which comprises: a heatable pellistor (20) for detecting combustible gases, a bridge circuit (20, 22, 24, 26), one arm of which incorporates the pellistor (20), the other arms incorporating resistors (22, 24, 26), an amplifier (32) for measuring the degree of imbalance in the bridge circuit and providing an output signal in accordance with the degree of imbalance, a regulator (28), which is preferably a switchmode regulator, for impressing a steady state potential across the bridge (20, 22, 24, 26); the regulator (28) is connected to receive the output signal from the amplifier (32) and to impress such a potential across the bridge (20, 22, 24, 26) that, if the bridge is balanced, tends to maintain the bridge in balance or, if the bridge is not balanced, tends to bring it into a balanced state, and means (44) for detecting the potential drop across the bridge (or a parameter varying therewith) and providing an output signal in accordance with the said potential drop, which signal gives a measure of the amount of a combustible gas in the atmosphere being monitored. The invention also provides a method for detecting the presence of a combustible gas in an atmosphere. |
