Appeal 2007-0128
Reexamination Control 90/006,208
Patent 5,573,648
ii. Counter Electrode: 2H+ + 2e- = H2 or 2H+ + 2 O2 + 2e- = H2O
(Id. at col. 2, line 65 to col. 3, line 5).
8) Dempsey=s gas sensor comprises a sensing electrode, a membrane, and a
counter electrode with the electrodes connected by a potentiostatic circuit.
Specifically, Dempsey states:
The various objectives and advantages of the invention are realized in
an electrochemical gas sensor of the solid polymer electrolyte type in
which the sensing and reference electrodes are mounted in close
proximity preferably on one side of a membrane. These electrodes
and a counter electrode on the other side of the membrane are
interconnected by a potentiostatic circuit which maintains the
potential
at the sensing electrode at the desired level for optinum [sic] oxidation
or reduction of the gaseous constituent to be sensed and maintains a
fixed potential difference between it and the reference electrode. The
electrodes are made similar in chemical and electrochemical structure
and are secured to the membrane in an identical fashion. The
reference and sensing electrodes though mounted in close proximity
on the membrane are situated so that the reference electrode is not in
the current flux field due to the current driven from the counter to the
sensing electrode by the potentiostatic circuit thereby eliminating
conditions which give rise to large background current variations with
temperature during zero-air operations.
(Id. at col. 1, line 61 to col. 2, line 13).
7
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