wtw pHotoFlex pH Operating Manual page 83

®
pHotoFlex pH
Measured value display
(calibration error)
No stable measured
ba75975e05 10/2017
Cause
----
Electrode:
– Diaphragm contaminated
– Membrane contaminated
– Moisture in the plug
– Not enough electrolyte
– Electrode obsolete
– Electrode broken
– Socket damp
Calibration procedure:
– Incorrect solution temperature
(without temperature sensor)
– Incorrect buffer solutions
– Buffer solutions too old
Cause
value
pH electrode:
– Diaphragm contaminated
– Membrane contaminated
Test sample
– pH value not stable
– Temperature not stable
Electrode + test sample:
– Conductivity too low
(e.g. in ultrapure water)
– Temperature too high
– Organic liquids
What to do if...
Remedy
– Clean diaphragm
– Clean membrane
– Dry plug
– Top up electrolyte
– Replace electrode
– Replace electrode
– Dry socket
– Set up correct temperature
– Select buffer solutions
suitable for the calibration
procedure
– Use only once.
Note the shelf life
Remedy
– Clean diaphragm
– Clean membrane
– Measure with air excluded if
necessary
– Temper if necessary
– Use suitable electrode
– Use suitable electrode
– Use suitable electrode
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