The INTERSCAN voltametric sensor (U.S. Patent number 4,017,373) is an electrochemical gas detector operating under diffusion controlled conditions. The 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.
An external voltage bias maintains a constant potential on the sensing electrode, relative to a nonpolarizable reference counterelectrode in the two-electrode Interscan sensor. Nonpolarizable means that the counterelectrode can sustain a current flow without suffering a change in potential. Thus, the counterelectrode acts also as a reference electrode, eliminating the need for a third electrode and a feedback circuit, as would be required for sensors using a polarizable air counterelectrode.
Interscan sensors—and gas analyzers—are available for
• carbon monoxide
• chlorine dioxide
• ethylene oxide
• hydrogen bromide
• hydrogen chloride
• hydrogen cyanide
• hydrogen peroxide
• hydrogen sulfide
• nitric oxide
• nitrogen dioxide
• peracetic acid
• propylene oxide
• sulfur dioxide
For more information on our analyzers, visit the Products section of this website