Pellistor

Principle

Pellistor is based on two thin platinum wires in aluminium beds connected to Wheatson bridge. One bed is covered with a special catalyst initiating oxidation of flammable gase (vapours), the other bed is modified to inhibit oxidation. The catalytic bed increases the temperature during the oxidation process in the presence of flammable gases (vapours). Oxidation process increases temperature of the bed with catalyst, which causes increase of resistance. The result of this status a bridge imbalance.

Benefits

• Linearn output up to 100% LEL
• Cheap and stable sensor
• Quick response time (< 10 s)
• Operation temperature: -40 to +60°C

Weaknesses

• Liable to poisoning and sensitivity decrease
• Required atmosphere with oxygen above 10% vol.
• Poisoned sensor gives output like sensor at zero concentration - requires regular span gas application
• Higher power consumption