1. Potentiometric measuring principles ABL800 FLEX Reference Manual
pCO
2
electrode, Continued
Designation
(continued)
E
0
(CO
2
,Gas1)
= Standard potential of the
pCO
2
electrode with Gas 1
E(CO
2
,Gas1,prev)
= Potential of the
pCO
2
electrode from the previous
measurement on Gas 1
δ
=
difference between
pCO
2
(sample) from the first and
last updatings.
predict
=
extrapolated value for
pCO
2
.
The pCO
2
electrode is calibrated on two gases with known CO
2
contents:
Sensitivity
Gas 1: 5.61 % CO
2
and Gas 2: 11.22 % CO
2
.
The exact composition of the calibration gases is contained in their bar codes.
The partial pressures of CO
2
in Gas 1 and Gas 2 are calculated from the following
equations:
)
pF BpCO CO
2 2 Gas 2 2
HO kPa() ()Gas Gas22=×−
The relative sensitivity of the
pCO
2
electrode is calculated as follows:
Sens( CO
E(CO ,Gas2) E(CO ,Gas1)
Sens( CO ,theo) log
CO (Gas2)
CO (Gas1)
2
22
2
2
2
p
p
p
p
) =
−
×
The sensitivity of the pCO
2
electrode should fall between 0.85 -1.00
or 85 - 100 %.
The status of the pCO
2
electrode is calculated as follows:
Status
kPa10(Gas1)CO)COStatus(
theo),COSens(
Gas1),(COEGas1),E(CO
22
2
202
p
pp
−
×=
The status of the pCO
2
electrode should fall between 6.2-260 mmHg /(0.83-34.66
kPa).
Drift
Drift 1 is calculated as follows:
kPa)prev(Gas1,CO10(Gas1)CO)CO1(Drift
2
theo),COSens(prev),COSens(
prev)Gas1,,E(COGas1),E(CO
22
22
22
ppp
pp
−×=
×
−
Drift 2 is calculated as follows:
kPa)prev(Gas2,CO10(Gas2)CO)CO2(Drift
2
theo),COSens(prev),COSens(
prev)Gas1,,E(COGas2),E(CO
22
22
22
ppp
pp
−×=
×
−
Continued on next page
1-16
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