Metrohm 840 PC Control 5.0 / Touch Control - Manual (Page 281)

4 Parameters
PC Control / Touch Control
269
Possible errors of the electrode test
Test criterion Message Measure
pH 9:
The drift in stirred solution is
> 1 mV.
General problem - Connect electrode.
- Replace defective elec-
trode cable.
- Clean diaphragm (see
electrode leaflet).
- Replace electrode.
pH 9:
–10 mV < U(unstirred)
< 10 mV
and
the sum of drift values after
1, 2, 3 und 4 min is
< 12 mV/min.
Short circuit Replace electrode.
A response time does not
meet the limit value for the
rating "Usable electrode".
Glass membrane / Dia-
phragm
Clean diaphragm (see elec-
trode leaflet).
The pH values are not de-
fined for all the buffers at the
measured temperature.
No buffer data Repeat electrode test at a
temperature at which the pH
values of all the buffers are
defined.
All the slopes meet the limit
values for the rating "Usable
electrode"
and
Uoff is outside the given lim-
its.
Unsuitable reference elec-
trode
- Repeat electrode test with
suitable reference system.
- Replace contaminated ref-
erence electrolyte.
- Select electrode type =
Custom and adjust limits
for Uoff.
The streaming potential is
too high.
Contaminated diaphragm Clean diaphragm (see elec-
trode leaflet).
Two slopes do not meet the
limit values for the rating
"Usable electrode".
Wrong buffer Repeat electrode test with
buffers pH 4, 7 und 9.
All the slopes do not meet
the limit values for the rating
"Usable electrode".
Partial short circuit Check temperature sensor
or enter correct calibration
temperature.