GE Monitor UPC-900 Operating Instructions Manual page 63

Calibrated electrode slope
A new electrode typically has a slope of 95% to 102% and an asymmetry potential
within ±30 mV. As the electrode ages, the slope decreases and the asymmetry potential
increases.
As a rule, when an electrode has an asymmetry potential outside of ±60 mV and a slope
lower than 80%, and no improvement can be achieved by cleaning, it should be replaced.
An electrode is still usable at lower slopes and higher asymmetry potentials but the re-
sponse will be slower and the accuracy diminished.
Part
1
2
3
Monitor UPC-900 Operating Instructions 29-0567-16 AB
1
Voltage (mV)
+500 mV
2
0 mV
–500 mV
Function
Voltage (mV)
Assymmetry
Calibration curve
pH
7
5 Operation
5.6 Calibrate the pH electrode
3
63