SCHOTT Instruments ProLab 2000 - Page 98

What to do if... ProLab 2000
98
ba75577e03 11/2009
No stable measured
value
Obviously incorrect
measured values
Buffer solutions:
– Incorrect buffer solutions –
– Change buffer solutions
– Buffer solutions too old – Use only once.
Note the shelf life
– Buffer solutions depleted – Change buffer solutions
Cause Remedy
Cause Remedy
pH electrode:
– Junction contaminated – Clean junction
– 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 a suitable electrode
– Temperature too high – Use a suitable electrode
– Organic liquids – Use a suitable electrode
Cause Remedy
pH electrode:
– Not connected – Connect electrode
– Cable broken – Replace electrode
– pH electrode unsuitable – Use a suitable electrode
– Temperature difference
between buffer and test
sample too high
– Adjust temperature of buffer
or sample solutions