Sensor principle of operation

The electrochemical sensor principle of operation is described as follows:

Gas molecules from the sample are adsorbed on an electrocatalytic sensing electrode, after passing through a diffusion medium, and are electrochemically reacted at an appropriate sensing electrode potential. This reaction generates an electric current directly proportional to the gas concentration. This current is converted to a voltage for meter or recorder readout.

The diffusion limited current, ilim, is directly proportional to the gas concentration according to the simplified equation…

ilim = nFADC

where ilim is the diffusion limited current in amps,    F is the Faraday constant (96,500 coulombs),    A is the reaction interfacial area in cm2,    n is the number of electrons per mole reactant,    δ is the diffusion path length,    C is the gas concentration in moles/cm3,    and D is the gas diffusion constant, representing the product of the permeability and solubility coefficients of the gas in the diffusion medium.


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