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Nernst Equation (%O2 Calculation)

Nernst EquationCalculation of oxygen concentration from SIRO2 sensor signal

Please enter the operating temperature (500 – 1700 deg C) and the measured mV (0 – 1200 mV) signal. The corresponding oxygen concentration is calculated. If it is very low, it is displayed in scientific notation.

Click here to download our Excel file for offline calculation

The Nernst equation is E = (RT/nF)ln(pO2/pO2‘)

E = sensor electromotive force, (mV)
R = gas constant
T = temperature, (Kelvin)
n = number of charges per reactant species
F = Faraday constant
p = partial pressure (mole fraction)

This equation describes the electromotive force (emf) developed when there are different concentrations of a reactant on each side of an electrolyte.

If oxygen is to be measured using a zirconia ceramic electrolyte and atmospheric air with pO2 = 0.209 as a reference, this equation simplifies to:

pO2 = 0.209 exp(-46.421 E/T)

The equation may be rearranged to allow calculation of the emf from a known reference concentration and a measured oxygen concentration:

E = 0.0496 T log(pO2/0.209)

Calculation of Nernst voltage from oxygen concentration

Note that the oxygen concentration can be entered either as a decimal fraction (so that 1% would be entered as 0.01) or in power of 10 notation ( so that 0.001% would be 1.00*10^-5).

ECONOX supplies a range of industrial, scientific and pottery probes for the measurement of oxygen at high temperature.