Pellistoren

Pellistoren, in English known as catalytic bead sensors or pellistors, are devices used to detect combustible gases in industrial and safety environments. They consist of one or more small beads with a catalytic coating, typically platinum, that are heated by an electrical current and wired into a measurement circuit such as a Wheatstone bridge.

Operating principle: when a combustible gas is present, it oxidizes on the heated catalytic surface, releasing heat. This extra heat raises the bead temperature and changes its electrical resistance, producing a signal that is proportional to the concentration of combustible gas. A non-catalytic compensation bead may be included to reduce the influence of ambient temperature and other environmental factors on the baseline signal.

Construction and use: a typical pellistor assembly includes a catalytic bead and a compensation bead within a protective housing. The device requires a supply of oxygen for oxidation and is commonly used in portable personal detectors and fixed gas monitoring systems. Calibration is performed with known gas concentrations to relate the sensor output to gas levels.

Applications: pellistoren are widely employed for detection of hydrocarbon gases such as methane, propane, and butanes in mining, oil and gas, chemical plants, and other environments with flammable atmospheres. They are valued for robustness, fast response, and relatively low cost, contributing to explosion-risk assessment and ventilation control.

Advantages and limitations: advantages include simple principle, broad response to many hydrocarbons, and suitability for harsh environments. Limitations involve limited selectivity (cross-sensitivity to various fuels), sensitivity to poisons and silicone-based compounds, dependence on ambient temperature and oxygen, and the need for regular calibration and maintenance to ensure accurate readings.