Hanna Instruments HI99163 Instruction Manual page 13

ELECTRODE CONDITION
The display is provided with a probe icon (unless the feature
is disabled from setup) which indicates the electrode status
after calibration. The "condition" remains active for 12
hours (unless the batteries are removed).
The electrode condition is evaluated only if the current
calibration has two points.
5 bars: excellent condition
4 bars: very good condition
3 bars: good condition
2 bars: fair condition
1 bar: poor condition
1 bar blinking: very poor condition
With 1 bar it is recommended to clean the electrode and
recalibrate. If there is still only 1 bar or 1 bar blinking
replace the probe.
Sensor Check
Setting the meter to pH‑mV range the user can check the
sensor status at any time. The offset value is the reading
in pH 7.01 buffer (@ 25 °C/77 °F). If this reading is
outside the range ±30 mV, the electrode is considered
"very poor". The slope value of the sensor is the difference
between readings in pH 7.01 and in pH 4.01 buffers. When
the slope reaches the value of about 150 mV, the electrode
is considered "very poor". When "poor" or "very poor", it
is recommended to replace it with a new one.
Note: To ensure reliable readings, the electrode must
be cleaned with cleaning solution and then hydrated in
storage solution for a minimum of 30 minutes before
calibrating the probe.
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