Other Possible Malfunctions - Testo 252 Bedienungsanleitung

32
Other possible malfunctions during measurement
Symptom:
Cause:
Symptom:
Cause:
Cause:
reference system through chemical
reactions and thus change the re-
ference potential or make it instable.
Cause:
whose zero point does not lie at
7. These electrodes can only be
used in the measuring mode "mV".
Cause:
The glass membrane can cause malfunction due to
the formation of physical coatings. These
coatings can alter the characteristics of the
electrode. Physical coatings and changes in the
membrance can take place in such a manner that
they are invisible to the naked eye. Damage of this
kind can take place e. g. in measuring solutions
with a flouride content, which corrode the glass
membrane.
pH measurement
Unstable measured value
Easily recognisable disturbances
such as broken electrode, broken
cable, formation of visible coatings
on the electrode, long-term
flooding of the connection head, etc.
Zero point of electrode outside
the tolerance (±60 mV at pH 7)
An incorrect or unusable buffer was
used during calibration.
Measuring solution which has pene-
trated the diaphragm can poison the
There are (a few) pH electrodes
The electrode was refilled with the
wrong reference electrolyte (type
02/05).
pH