wtw Multi 197i - Page 68

What to do if... Multi 197i
68
ba75339e04 07/2009
No stable measured
value
Obviously incorrect
measured values
Buffer solutions
– Incorrect buffer solutions – Change calibration procedure
– Buffer solutions too old – Use only once.
Note the shelf life
– Buffer solutions depleted – Change solutions
Cause Remedy
pH electrode:
– Diaphragm contaminated – Clean diaphragm
– Membrane contaminated – Clean membrane
Test sample:
– pH value not stable – Measure with air excluded if
necessary
– Temperature not stable – Adjust temperature if
necessary
Electrode + test sample:
– Conductivity too low – Use suitable electrode
– Temperature too high – Use suitable electrode
– Organic liquids – Use suitable electrode
Cause Remedy
pH electrode:
– pH electrode unsuitable – Use suitable electrode
– Temperature difference
between buffer and test
sample too high
– Adjust temperature of buffers
or sample
– Measurement procedure not
suitable
– Follow special procedure