Xylem YSI VARiON Plus 700 IQ H, Operating Manual, Page: 46 / 62

What to do if ... VARiON
® Plus
700 IQ H
46
ba76207e02 12/2020
8 What to do if ...
8.1 Interpretation of the drift voltage
The drift voltage is influenced by the potential levels of the measure-
ment electrode and reference electrode. If the potential levels shift, e.g.
caused by aging, both parts can move into the same direction or into
opposite directions. The comparison of the drift voltages of two or three
electrodes enables to draw conclusions concerning the state of indi-
vidual electrodes if a matrix adjustment or calibration resulted in an
invalid or considerably deviating drift voltage.
Assessment aids View the calibration history of the electrodes. In the following cases,
assessment is relatively easy:
 If the drift voltages of all electrodes show the same trend, i. e. the
drift voltages have shifted in the same direction (positive or nega-
tive) by approximately the same amount, this indicates that the
potential level of the reference electrode has shifted. The reference
electrode is possibly highly contaminated or at the end of its service
life.
 If the drift voltages of all electrodes do not show a trend but shift by
different amounts into different directions, the potential level of the
reference electrode has not changed considerably. The invalid drift
voltage is probably caused by a defective measuring electrode. The
measuring electrode is possibly highly contaminated or at the end of
its service life.