CALORIMETRY
ACCURATE COMBUSTIBLES MEASUREMENTS
The sensor measures combustibles ( COe ) from its exothermic reaction with oxygen ( O 2 ) over a catalytic platinum surface , which produces carbon dioxide ( CO 2 ) and the heat generated is used to determine the COe concentration .
A four quadrant bridge track is over-glazed to shield the circuit from the sample gas and two quadrants are then coated in platinum catalyst . These quadrants form a Wheatstone bridge circuit , with the disc mounted in a cell heated to 300 o C ( 572 o F ) or 400 o C ( 752 o F ).
When the gas sample is added , any COe present in the sample will combust on the catalyst , which will heat the respective quadrant and alter the Wheatstone bridge output voltage .
The output delivered will be directly proportional to the COe concentration , providing an accurate measurement .
WHEATSTONE BRIDGE
P72