Electrochemical gauge for oxygen having an internal reference and solid electrolyte

DETAILED DESCRIPTION However, it has now been established that it is possible to overcome, at least to a large extent, the disadvantages of such known gauges by using as the internal reference a new redox couple of the metal-metal oxide type.
The invention seeks to provide a new redox system which may be useful in providing an internal reference for an oxygen gauge.
According to another aspect the invention provides an oxygen gauge equipped with such an internal reference and several methods of construction of such a gauge.
According to a further aspect of the invention, there is provided a method of using such gauges in the determination of the composition of gaseous mixtures, particularly in determining the composition of combustion gases and especially in the determination of the P.
sub.
CO /P.
sub.
CO2 ratio.
The invention also concerns the application of the gauges to the regulation of the composition of gaseous fuel mixtures and of gaseous combustive-combustible mixtures.
According to the invention there is provided a redox system capable of establishing an internal reference of an electrochemical gauge for determining oxygen pressures, which redox system comprises a mixture of lead (Pb) and lead oxide (PbO) capable of reacting according to the equilibrium: Pb+1/2O.
sub.
2 .
revreaction.
PbO This Pb:PbO redox system is capable of providing, at a given temperature, a well defined oxygen pressure which can be used as a reference pressure.
It has the advantages of being in thermodynamic equilibrium over a range of temperatures of from about 400.
degree.
to 1500.
degree.
C.
, and of rapidly returning to a new equilibrium state when the temperature varies.
It can thus be used without any inconvenience in conditions where the operating temperature is not stable.
The study of the Pb:PbO system by the inventors has shown that it is of particular interest for use as an internal reference.
In fact, the characteristics of its equilibrium constant are such that the oxygen pressure that it establishes is dependant only on the temperature, but the function defining the variation of this oxygen pressure with temperature is practically identical to that defining the oxygen pressure associated with the equilibrium: CO+1/2O