How Does a Gas Sniffer Work?

Google for pellistor, Mr Wiki has a nice article about it.

I now have more time to answer.

The pellistor is a catalyst loaded ceramic blob on a wire that changes resistance when heated. The molecules of the gas is "burned" when thy enter the blob and causes a temperature change.

The pellistor on its own are not capable of detecting gas because it also changes with temperature etc. a method must then be devised to deduct external effects before the true gas value can be exported.

But that is electronic design and the circuit in your snifter may work on another principle.

Thanks for the link to wiki and the explanation. Now lets see if I understand it.

Electrical resistance will change in the pellistor due to the heat generated by the burning of a combustable gas. The generated variance in the temperature will be directly proportional to the amount of the gas present, and the temperature change is measured by the change in electrical resistance.

So the amount of gas is revealed by an electrical process (change in measurable resistance) not by a process involving optical radiations, (spectrometrics etc.)

That gives me my tariff number, and a new word for my vocabulary (pellistor) , thus making it all worth getting out of bed today. Thank you.

Pleasure