Hanna Instruments HI 8711 - Manual (Page 31)

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HI 8510, HI 8710 and HI 8711 are provided with autodiagnostic
functions that allow to check and troubleshoot any malfunctioning.
The functions are made via front panel keys to isolate the cause of
malfunction whether it is due to pH electrode contamination, internal
offset circuit or amplifier circuit.
Follow the procedure described below.
First press the MEASURE key, then one of the
following keys.
A) Sensor Test
Immerse the electrode in pH 7.01 buffer
solution (HI 7007), press SENSOR TEST
key and the display shows the mV
response of the electrode.
The corresponding LED turns on.
If the electrode is in good working condition, the value should be
within ±30 mV.
A value between 30 and 60 mV or -60 and -30 mV, indicates
some contamination of the electrode.
If the value is higher than 60 mV or lower than -60 mV, the
contamination is too high and the electrode should be replaced.
B) Internal Offset Circuit Test
Press the pH 7 TEST key and the display should show a value
within 7±1 pH, to verify the internal circuit of the meter in
terms of the offset compensation.
The corresponding LED turns on.
pppppH DIAGNOSTIC TESTS H DIAGNOSTIC TESTS H DIAGNOSTIC TESTS H DIAGNOSTIC TESTS H DIAGNOSTIC TESTS