Pellistor type PC is designed to use in devices measuring concentrations of gas and flammable vapours, in explosimeters and systems of monitoring explosion hazard etc. Devices with PC detectors may be applicated in many industries where is the must of monitoring explosive gas concentration, e.g. mining, chemical industry, petrochemistry, municipal economy etc.
The operation of the pellistor is based on catalytic combustion (measuring range up to 100% LEL) or on heat conductivity difference between the measured and reference gases (measuring range up to 100% V/V). The right detector’s operation conditions requaire to protect it against direct exposure to poisoning compounds and inhibitors (e.g. silicones, chlorides, lead, cadmium).
The pellistors are working in Wheatstone’a bridge (as shown in Figure), powered by DC voltage.
Catalytic detector consists of active element (SA) and compensative element (SK). Compensative element (SK) with compensative resistor (RK), minimize the influence of outside factors (interfering gases, temperature, moisture, etc.) on the detector’s operation. The difference between temperature of active element on which methane is combusted against compensative element temperature generates the unbalanced bridge signal related to gas concentration.
Thermoconductive detector consists of measurement element (SP) and reference element (SR). The difference of heat conductivity between the measured gas and the reference air hermetically closed in its housing generates the unbalanced bridge signal related to the gas concentration.