Calibration
Operation
Calibration
solutions
Solutions for calibration of conductivity measuring devices
are unbuffered systems. Care should be taken to use fresh
conductivity standards and to avoid contamination of the
conductivity standard by water droplets adhering to the
conductivity sensor.
Clean sensors Before calibration, make sure that the conductivity sensor
is clean. Residues should be rinsed off with distilled water.
Afterwards, the sensor should be wiped dry and rinsed
with the calibration solution to be used.
Cell constant
The cell constant is determined by the size and geometric
arrangement of the measuring electrodes. It is the charac-
teristic parameter of conductivity sensors. The cell constant
changes very little over time. The prerequisite is clean elec-
trode surfaces without insulating deposits. Regular calibra-
tion is therefore generally not necessary.
4-electrode
sensors
With 4-electrode sensors the principle of separate current/
voltage electrodes results in virtually no measuring errors
even in the case of partial soiling of the measuring elec-
trodes. However, electrodes completely soiled with insulat-
ing coatings cause the measurement to fail.
2-electrode
sensors
With 2-electrode sensors for the measurement of low con-
ductivities, e.g. ultrapure water, no calibration with calibra-
tion solutions is possible in practice, as calibration solu-
tions with a correspondingly low conductivity do not have
a stable conductivity value. The use of calibration solutions
with a higher conductivity (> 200 S/cm) would lead to con-
siderable polarization errors. Therefore, the cell constant
must be entered manually when using 2-electrode sensors.
By calibration, the Portamess® 913 (X) Cond is adjusted to
the cell constant of the sensor.
It is generally sufficient to enter the cell constant specified
by the sensor manufacturer.
General information on calibration
