17.2 pH and mV Troubleshooting
Symptom Possible Causes Remedy
Unit fails to calibrate, even
with new probe.
Calibration settings outside of
allowable limits due to previous
failed calibration.
Initialise the unit. See section 15.
1 Point calibration fails.
(pH asymmetry is greater
than ±1.00 pH, or mV offset
is greater than ±60mV).
1. Reference junction blocked.
2. Reference electrolyte
contaminated.
Clean reference junction as per instructions
supplied with the pH or reference electrode.
Flush with distilled water and replace
electrolyte.
2 Point calibration fails.
(pH slope is less than
85.0%.)
3 Point pH calibration fails.
(pH SlopeB is less than
85.0%).
1. pH Buffers not correctly set.
2. pH glass bulb not clean.
3. Electrode is aged.
4. Connector is damp.
5. pH Buffers are inaccurate.
For automatic pH buffer recognition, ensure
that you are using buffers that match the
selected buffer set (see section 4.2).
Otherwise, ensure that the buffer value is
entered correctly at pH calibration.
Clean pH glass bulb as per instructions
supplied with the electrode.
Attempt rejuvenation as per instructions
supplied with the electrode. If unsuccessful,
replace electrode.
Dry in a warm place.
Replace standards or buffers.
Unstable readings. 1. Reference Electrolyte
chamber needs to be refilled.
2. Reference junction blocked.
3. pH glass bulb not clean.
4. Bubble in pH glass bulb.
5. Faulty connection to meter.
6. Reference junction not
immersed.
7. KCl crystals around
reference junction inside the
electrolyte chamber.
Refill with saturated KCl filling solution.
Clean reference junction as per instructions
supplied with the electrode.
Clean glass bulb as per instructions
supplied with the electrode.
Flick the electrode to remove bubble.
Check connectors. Replace if necessary.
Ensure that the reference junction is fully
immersed. See diagrams in sections 4.4,
5.2, & 6.2.
Rinse electrolyte chamber with warm
distilled water until dissolved. Replace
electrolyte.
Inaccurate readings, even
when calibration is
successful.
Reference junction blocked. Clean reference junction as per instructions
supplied with the electrode.
Displays constant reading
around pH7.00 or 0mV for
all solutions.
Electrical short in connector. 1. Check connector. Replace if necessary.
2. Replace electrode.
Displays 4-5 pH for all
solutions.
pH electrode glass bulb or
internal stem cracked.
Replace pH electrode.
Reading does not change in
any sample being measured
Auto Stability Function has
frozen display (notice the ).
Turn Auto Stability Function OFF or re-
start sampling (see section 8).
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