JUMO 202931, Operating Manual, Page: 13 / 20

13
5 Calibrate
5 Calibrate
5.1 General information
Depending on production, the cell constants of commercial conductivity sensors are subject to a certain
level of dispersion. When a more accurate measurement is required, the sensor, measuring line and
transmitter have to be coordinated. This coordination is achieved through calibration.
To achieve optimum accuracy, we recommend performing the calibration in the same conductivity range
in which the measurement will be conducted.
Furthermore, the cell constant of a conductivity sensor can change through ageing and, in particular,
through dirtying of the electrodes (coatings).
That is why it is necessary to clean the sensor and calibrate the transmitter on the conductivity sensor
at regular intervals. The frequency of this depends on the measurement medium and the operating con-
ditions.
NOTE!
Before conducting the calibration, make sure that the sensor is clean and in perfect working condition.
5.2 Settings on the transmitter/controller
NOTE!
For the calibration, it is essential that you observe the operating manual of the transmitter/controller used
(e.g. JUMO AQUIS 500 CR, JUMO dTRANS CR 02, JUMO AQUIS touch S/P or JUMO digiLine CR with
separate sensor).
At least the following settings are required:
•
Cell type (connection type): 4-electrode or 4-wire
• Nominal cell constant: 0.5
1
cm
-1
Reference solutions
A reference solution is used to calibrate the relative cell constant.
The conductivity of commercial potassium chloride reference solutions include e.g.:
To ensure the measurement is as accurate as possible, the reference solution chosen must be close to
the setpoint of the conductivity measurement when in operation.
When performing the calibration, proceed as instructed in the operating manual for the transmitter/con-
troller used.
1
Value for AQUIS 500 CR and dTRANS CR 02; for AQUIS touch and digiLine CR the value 0.25 can
be entered manually for this sensor.
Potassium chloride concentration Conductivity at 20 °C Conductivity at 25 °C
C
(KCl)
= 0.01 mol/l 1278 µS/cm 1413 µS/cm
C
(KCl)
= 0.1 mol/l 12.2 mS/cm 12.9 mS/cm
C
(KCl)
= 3 mol/l 275 mS/cm 298 mS/cm