Hach-Lange ISENH318103 User Manual - Manual (Page 12)

Message or symptom Possible cause Action
Drifting/inaccurate readings
Dirty sensing element Clean the probe (body, membrane module and glass
bulb).
Clogged reference Rinse reference junction with deionized water
thoroughly and shake the probe downward to
remove any air bubbles.
Samples lose ammonia content Measure samples and standards within 15 minutes
after ISA is added (ammonia gas can escape from
the solution). Add Parafilm over the top of the
samples and standards to reduce Ammonia loss. Cut
a hole for the electrode.
Improper storage conditions Clean or condition the probe (refer to Clean the
probe on page 10) and attempt another calibration.
To re-condition the probe and reference junctions,
allow the probe to soak in ammonia probe storage
solution for at least 30 minutes prior to use.
Membrane failure Replace the membrane module.
Stabilization criteria not optimized
for the application Adjust the stabilization criteria in the measurement
options menu.
Magnetic stirrers may generate
sufficient heat to change solution
temperature. Put a piece of insulating material between the stirrer
and beaker.
Damaged probe Contact a Technical Support Representative.
Electromagnetic Forces (EMF) such
as voltaic cells, thermoelectric
devices, electrical generators,
resistors and transformers Do not use in areas where EMF is present.
Insufficient amount of filling solution Add filling solution.
Colloidal and/or particles in the
filling solution. Replace the filling solution, calibrate and retest.
Bubbles trapped under sensor tip Gently shake the probe until bubbles are removed
from under sensor tip.
Temperatures of calibration
standards and samples are not
within ±2 °C of each other. Make sure that the temperatures are within ±2 °C of
each other.
Out of range Measurement value is outside of
range Make sure that the sample is within the range of the
probe.
Out of limits
Check standard value is outside of
limits set in the current method Make sure that the standard is within the limits of the
current method.
Make another method that expands the acceptable
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.
Make a new method with an expanded range.
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