Complete Selection of Calibration Gas & Equipment


Catalytic Vs Infrared 

The two most common combustible gas sensing technologies are catalytic and infrared.

Catalytic Detectors are based on the principle that when gas oxidizes it produces heat and the sensor converts the temperature change via a standard Wheatstone Bridge-type circuit to a sensor signal that is proportional to the gas concentration.  The sensor components consist of a pair of heating coils (reference and active).  The "active element" is embedded in a catalyst.  The reaction takes place on the surface of the catalyst, with combustible gases reacting exothermically with oxygen in the air to raise its temperature.  This results in a change of resistance.  The "reference element" provides an inert reference signal by remaining non-responsive to gas, thereby acting as a stable "baseline" signal to compensate for environmental changes which would otherwise affect the sensors temperature.

You may find all of this very interesting but are wondering what any of this has to do with calibration gas!

Answer: One of the disadvantages of a Catalytic Detector is that it requires the presence of Oxygen (O2) for the detection principle to work.  Therefore, if your gas detection instrument has a catalytic type LEL sensor, the calibration gas that you order must contain some Oxygen - we would recommend a minimum of 12%.  For example, you will not be able to calibrate an instrument that has a catalytic type LEL sensor if you purchase 50% LEL Methane (CH4) with a Nitrogen balance.  

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