| 摘要 |
<p>Apparatus (10) for detecting combustible gaseous hydrocarbons comprises a chamber (12) for receiving gaseous samples and an electric circuit (13) incorporating first and second pellistors (14, 15) housed within the chamber (12). Pellistor (14) has a catalytic coating. Circuit (13) has constant current source (20) delivering its current output to the pellistors (14, 15) which are series connected and, in parallel therewith, to a pair of high value reference resistors (21, 22) which are also series connected. A first voltage measuring device (26) is connected between the inter-pellistor junction and the inter-resistor junction and provies an LEL measurement. A second voltage measuring device (29) is connected across pellistor (15) and provides a volume gas measurement.</p> |
