Technical Description
REACTIONS OF CHEMICAL ABSORPTION
Reactions which occur between the oxygen in the atmosphere and the surface are the
following:
O
2
+ e
-
↔
O
2
-
(ads)
O
2
↔
2 O
(ads)
e
-
+ O
(ads)
↔
O
-
(ads)
The reactions which occur in presence of a reducing gas are the following:
R
ed
+ O
-
(ads)
→
R
ed
O
-
(ads)
→
R
ed
O + e
-
R
ed
= reducing gas
ANALITICAL EXPRESSION OF THE SENSOR MEASUREMENT
The reaction between the resistance of the sensor and the concentration of the
reducing gas can be expressed by the following equation:
R = A[C]
-
α
R = electrical resistance of the sensor
A,
α
= constants
[C] = gas concentration
In terms of conduttance, the relation with the gas concentration is expressed by a
power law: :
G
g
= G
a
+
α
[C]
β
G
g
= conductance in a gas
G
a
= conductance in air
α
,
β
= constant
[C] = gas concentration
ORION S.r.l.
ETL_Operation and Service manual_ 02_17.docx
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