Sartorius Docu-pH - Error Messages

Error Messages
If the meter displays a calibration error:
this indicates an error in the electrode reaction.
If this is displayed during calibration, this means
the electrode shows under 90% or over 105% of the
correct slope according to the Nernst equation.
The “Error” message can mean one of the following:
– A bad electrode
– One or more contaminated or expired buffer(s)
– Wrong buffer selected
– mV offset greater than |30|mV
Testing a pH electrode:
§ Immerse the electrode in a good neutral pH 7 buffer.
§ Access mV mode: Press softkey mV
> Record the measured value
$ Make sure the portable meter is in the mV mode and
not in the relative mV mode (rel. MV). Repeat these
steps with basic or acidic buffers. At a temperature
of approx. 25°C, the electrode signal should be
within the limits shown here:
32
Zero point at Slope Cause Solution
pH = 7.00
1)
Between –30 mV 53…62 mV/∆pH Electrode OK
and +30 mV 90...105 % of the
theoretical value
Between < 10 mV/
∆pH Glass membrane Replace electrode
–55...–65 mV or < 17 % of the ruptured
+55...65 mV theoretical value
< –30 mV and 53…62 mV/
∆pH Wrong or Replace electrolyte.
> +30 mV 90...105 % of the contaminated Not possible with gel-
theoretical value electrolyte filled electrodes
– here: replace electrode.
Between –30 mV 15…50 mV/
∆pH Membrane aged Regenerate membrane
and +30 mV 25...85 % of the (see manual of the electrode
theoretical value or replace electrode).
< –30 mV and 15…50 mV/
∆pH Membrane Clean electrode carefully
> +30 mV 25...85 % of the or junction dirty (see electrode manual).
theoretical value
> 62 mV/∆pH Buffer error Throw out buffer.
Recalibrate with
fresh buffer.
1) for pH = 6.86, added 8 mV to the values.
Error