wtw Multi 9420 - Page 115

Multi 9420 What to do if...
ba75964e04 04/2015 115
No stable measured
value
Obviously incorrect
measured values
Cause Remedy
IDS pH sensor:
– 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
IDS pH sensor + test sample:
– Conductivity too low – Use suitable IDS pH sensor
– Temperature too high – Use suitable IDS pH sensor
– Organic liquids – Use suitable IDS pH sensor
Cause Remedy
IDS pH sensor:
– IDS pH sensor unsuitable – Use suitable IDS sensor
– Temperature difference between
buffer and test sample too great
– Adjust temperature of buffer or
sample solutions
– Measurement procedure not suit-
able
– Follow special procedure