details about two sensors

[renikanna]

i need a details about harmonic sensor and gas sensor.. principle of working and what type of function process inside the sensors...

 

[vicky001.iith]

I don't have knowledge about harmonic sensor.while i have used gas sensor many times.So i will help you with it.
Gas sensor :- first it has many different types and each has different type of functionalities.

You read this basic pdf where type and function of sensors is explained :-

http://www.thomasnet.com/articles/instruments-controls/How-Gas-Detectors-Work

If want more into details read this one :-

http://www.hse.gov.uk/pubns/gasdetector.pdf