Hach-Lange PHC20103 User Manual - Manual (Page 11)

Message or symptom Possible cause Action
Calibration errors Calibration not done correctly Recalibrate using freshly prepared pH buffers.
Contaminated glass sensor Clean the probe (refer to Clean the probe on page 9).
Slope exceeds the criteria for % of
theoretical (as defined in the method
slope limit)
1. Widen the slope limits by changing the PHC201
calibration settings and method.
2. Recalibrate the probe.
3. Run a check standard to check the performance of the
probe.
Drifting/Inaccurate
readings Contaminated glass sensor Clean the probe (refer to Clean the probe on page 9).
CO
2
absorption (for low ionic
strength or high purity sample)
Use the LIS chamber for LIS/high purity samples to keep
sample contamination from occuring.
Air bubbles around inner reference
electrode Rinse the reference junction holes with deionized water and
then gently tap the probe with hand or shake the probe to
remove any air bubbles.
Incorrect storage conditions
(discolored, contaminated or dried
semi-liquid gel) Clean or condition the probe and do recalibration. The probe
may not operate correctly if the probe has been left dry for a
long time. Condition the glass sensor and reference junction
again:
1. Soak the probe tip in the 4.01, 7.00 and 10.01 buffers each
for 5 minutes.
2. Rinse with deionized water. Blot dry with a lint-free cloth.
3. Calibrate the probe.
Electromagnetic Forces (EMF) such
as voltaic cells, thermoelectric
devices, eletrical generators,
resistors and transformers. Do not test in areas where EMF is present. For testing in
process units (i.e. spot checking), make sure the equipment is
grounded.
Out of range Measurement value is outside of
range Make sure that the sample is within the range of the probe.
Temperature out of
range Temperature value is outside of
range Make sure that the sample temperature is within the range of
the probe.
Make sure that the temperature sensor is working correctly.
Measured pH buffer temperature is
outside range of the probe Make sure that the standard temperature is within the range of
the probe.
Make sure that the temperature sensor is working correctly.
Check standard temperature value
is outside of range Make sure that the Check Standard temperature is within the
range of the probe.
Out of limits Measurement value is outside of
measurement limits set in the current
method Make sure that the sample is within the limits of the current
method.
Create a new method with expanded limits.
Check standard value is outside of
limits set in the current method Make sure that the check standard is within the limits of the
current method.
Create another method that expands the acceptable limits.
DOC022.52.80197 11