RADIOMETER FLEX ABL90, Reference Manual

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ABL90 FLEX reference manual 5. Sensors and optical system
5-7
Sensitivity
The electrode sensitivity illustrates the slope of the calibration line compared to
the slope of the theoretical electrode.
The sensitivity of the theoretical electrode is 100 % or 1.00.
Theoretical calibration line
Slope=  61.5 mV/pH
Sensitivity = 100 %
pH
Measured
potential
(mV)
65.25
96
6.8
7.3
2-point calibration line
Slope =  58.4 mV/pH
Sensitivity = 95 %
If an electrode has a sensitivity of 95 % or 0.95, its sensitivity is 5 % lower than
the sensitivity of the theoretical electrode.
The sensitivity of an electrode is calculated as:


 
Potential at 6.8 Potential at 7.3
Sensitivity (%)
61.5 (7.3 6.8)
where 61.5 = sensitivity of theoretical electrode.
Each electrode has its own sensitivity limits.
The sensitivities are range checked:
pH p CO
2
pO
2
c K
+
c Na
+
cCa
2+
cCl
–
c Glu c Lac
% % % % % % % pA/mmol/L pA/mmol/L
Min. 85 60 85 85 85 85 75 100 100
Max. 105 105 105 105 105 105 105 2000 2000
The calibration line slope is re-established with every calibration.
The slope of the calibration line is described by the sensitivity value.
The calibration status values are, in general, defined as the sensor signals of
CAL 1, except for pO
2
, which is only calibrated in one point (pO
2
status reflects
the cal check):
pH p CO
2
pO
2
c K
+
c Na
+
cCa
2+
cCl
–
cGlu c Lac
mV mV mmHg mV mV mV mV pA pA
Min. -50 -50 -20 150 150 200 -50 0 0
Max. 250 250 20 350 350 400 100 3000 3000
Drift describes the variation in location of the calibration line between
consecutive calibrations. Typically, sensitivity drift is insignificant compared to
status drift. The analyzer automatically compensates for this drift by performing
a 1-point calibration with every measurement.
Definition
Updating
Sensitivity
Status
Drift