Hach-Lange PHC28103 - Manual (Page 12)

Message or symptom Possible cause Action
Slow stabilization time Tape not removed from the filling-
hole Remove the tape that is over the filling hole.
Contaminated glass sensor Clean the probe (refer to Clean the probe on page 10).
Contaminated filling solution Drain and replace the filling solution with fresh solution.
Filling hole closed Open the filling hole while in use by removing the filling-
hole cap from the filling hole.
Poor contact between reference
junction and solution Shake the probe in the solution from side to side to
refresh the reference junction.
Probe not prepared for LIS sample For the best stabilization time, soak the probe in the
sample for 1 to 3 minutes before the initial measurement.
Low sample temperature or
temperature difference between
samples Check the sample temperature. The lower the
temperature or the greater the difference of temperatures
between samples, the longer the stabilization time will
be.
Air bubbles around inner
reference electrode Gently tap the probe with hand or shake the probe
downward to remove any air bubbles.
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 10).
Slope exceeds the criteria for % of
theoretical (as defined in the
method slope limit)
1. Widen the slope limits by changing the PHC281
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 bulb Clean the probe (refer to Clean the probe on page 10).
CO
2
absorption (for low ionic
strength or high purity sample)
Use the LIS chamber for LIS/high purity samples to
prevent sample contamination.
Clogged reference 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.
Improper storage conditions/
Dehydrated glass bulb 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 junctions 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, electrical
generators, resistors and
transformers Do not test in areas where EMF is present. For testing in
process units (spot checking), make sure that the
equipment is grounded.
Colloidal and/or particulates in the
filling solution. Replace the filling solution, calibrate and test again.
Air bubbles around inner
reference electrode Gently tap the probe with hand or shake the probe
downward to remove any air bubbles.
Out of range Measurement value is outside of
range Make sure that the sample is within the range of the
probe.
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