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10.2 pH and mV Troubleshooting
Symptom
Possible Causes
Remedy
Meter displays
"
OverR
OverR
" as a pH
reading.
pH reading is over-ranged.
pH sensor not connected or
faulty. Replace sensor if
necessary.
Unit fails to
calibrate, even with
new sensor.
Calibration settings outside of
allowable limits due to previous
failed calibration.
Initialise the unit. See section 9.
1 Point calibration
fails (Asymmetry is
greater than +/-1.00
pH).
1.
Reference junction blocked.
2.
Reference electrolyte
contaminated.
Clean reference junction as per
instructions supplied with the
sensor.
Flush with distilled water and
replace electrolyte.
2 Point calibration
fails (Slope is less
than 85.0%).
1.
Buffer set incorrectly.
2.
Glass bulb not clean.
3.
Sensor is aged.
4.
Connector is damp.
5.
Buffers are inaccurate.
Ensure that you are using
buffers that match the selected
buffer set. See section 8.
Clean glass bulb as per
instructions supplied with the
sensor.
Attempt rejuvenation, as per
instructions supplied with the
sensor. If not successful,
replace sensor.
Dry in a warm place.
Replace buffers.
Inaccurate readings,
even when
calibration is
successful.
Reference junction blocked.
Clean reference junction as per
instructions supplied with the
sensor.
Displays 7.00 for all
solutions.
Electrical short in connector.
1.
Check connector. Replace if
necessary.
2.
Replace sensor.
Displays 4-5 pH for
all solutions.
Glass bulb or internal stem
cracked.
Replace sensor.
