Campbell CS526 Instruction Manual - 11. Maintenance
CS526 ISFET pH Probe
Problem:
Probe signal is drifting.
Possible reasons:
o Diaphragm can be dried out.
o Chip is scratched.
Suggestions:
o Soak probe for 10 minutes in saturated KCl solution (pn 16349).
o Probe cannot be fixed if chip is scratched.
11. Maintenance
The CS526 needs to be periodically cleaned and calibrated
to ensure accurate readings and proper operation.
CAUTION
The CS526 has no user-serviceable parts.
11.1 Cleaning
Proper maintenance of a probe is important. If the probe is not properly and
regularly cleaned, the probe can malfunction due to a contaminated diaphragm
or ISFET chip. Contamination on/or blockage of the sensor and reference
electrode diaphragm surface is the most likely cause for probe failure.
Probe wear is another cause for probe failure. Probe wear is often, but not
necessarily, preceded by a period of declining calibration slope values. Probe
wear is dependent on how the probe is used and stored (see Section 11.2,
Storage). Worn probes need to be replaced.
11.1.1 When to Clean
Often the probe should be cleaned daily, but the appropriate cleaning frequency
is dependent on the type of sample being measured.
Clean the probe if any of the following occur:
• Low slope
• Drift
• Instability of the reading
• Slow calibration
• Probe will not calibrate
• pH value doesn’t change as expected when changing samples
Additionally, when sampling colored liquids, the probe should be cleaned
when the reference diaphragm is no longer white.
9