Hach-Lange PHC725 - Manual (Page 14)

Message or symptom Possible cause Action
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 Make sure that the filling hole is not covered. Rinse the
reference junction holes with deionized water. Carefully
tap the probe with hand or shake the probe to remove air
bubbles. If there are salt crystals around the junction,
soak the electrode tip in a 60 ºC (140 ºF) water bath for
10 minutes.
Improper storage conditions/
Dehydrated glass bulb Clean or condition the probe and calibrate again. The
probe can not operate correctly if the probe was left dry
for a long time. Rehydrate the probe. Refer to
Storage
on page 11.
Colloidal and/or particulates in
the filling solution Replace the filling solution, calibrate and test again.
Air bubbles around inner
reference electrode Carefully tap the probe with hand or shake the probe to
remove air bubbles.
Not sufficient electrolyte flow 1 Open the sleeve junction.
Not sufficient stirring Stir the standards and samples at a slow and steady rate
to prevent the formation of a vortex.
Out of range Measurement value is out of
range Make sure that the sample is in the range of the probe.
Out of limits Check Standard value is out of
limits in the current method Make sure that the standard is in the limits of the current
method.
Do another method that expands the acceptable limits.
Measurement value is out of
measurement limits in the current
method Make sure that the sample is in the limits of the current
method.
Make a new method with an expanded range.
Temperature out of range Temperature value is out of
range Make sure that the sample temperature is in the range of
the probe.
Make sure that the temperature sensor works correctly.
Measured temperature is out the
range of the probe Make sure that the standard temperature is in the range
of the probe.
Make sure that the temperature sensor works correctly.
Check standard temperature
value is out of range Make sure that the check standard temperature is in the
range of the probe.
1 Only applicable for probes with sleeve junction.
Consumables and accessories
Description Quantity Item Number
Electrode filling solution, saturated KCl 59 mL 25118059
Electrode filling solution, saturated KCl 500 mL 25118049
KCl crystals (Radiometer Analytical) 15 g S21M001
Hach Electrode Cleaning Solution 500 mL 2965249
EDTA standard solution, 0.20N 500 mL 102149
Soaker bottle 1 5192900
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