pellistorbased

Pellistor-based sensors are gas detectors that rely on catalytic combustion on a heated bead, known as a pellistor, to sense flammable gases. In a typical arrangement the active bead is part of a Wheatstone bridge along with a matching reference bead. The catalytic bead is coated with a platinum or palladium catalyst and heated to several hundred degrees Celsius. When a combustible gas penetrates the protective coating, it oxidizes on the catalyst, releasing heat. The resulting temperature rise changes the bead’s electrical resistance, unbalancing the bridge and producing an electrical signal that is correlated to gas concentration, usually expressed as a percentage of the lower explosive limit (LEL).

Pellistor-based sensors are commonly used in fixed safety gas detectors and portable instruments in industries such as oil and gas, chemical processing, mining, and utilities. They are valued for rugged operation, short response times, and relatively low cost, and they can measure a broad range of hydrocarbon fuels, including methane, propane, and gasoline vapors. Calibration is typically done with a known gas such as methane, and readings are expressed as percent LEL or sometimes percent of gas concentration depending on the detector. However, their performance depends on oxygen availability and they can be poisoned by certain contaminants such as silicones and sulfur compounds. They also exhibit cross-sensitivity to some gases and are less selective than some modern sensor types.

In practice, pellistor-based detectors are often paired with other sensor technologies to improve specificity and safety. Material advances include more durable catalysts and protective coatings, and device designs emphasize redundancy, automatic self-test, and compatibility with intrinsically safe instrumentation in hazardous areas.