Cond 1970i
Operation
21
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07/2009
4.3
Determining/setting up the cell constant [C]
Why determine/set up
the cell constant?
Aging slightly changes the characteristics of the cell, e. g. by coatings.
As a result, an inexact measured value is displayed. The original char-
acteristics of the cell can often be restored by cleaning the cell. Calibra-
tion determines the current cell constant and stores it in the instrument.
Thus, you should calibrate at regular intervals (we recommend: every
6 months).
Procedure
The cell constant is determined in the control standard, 0.01 mol/l KCl.
You can determine the actual cell constant of the conductivity measur-
ing cell by calibrating with the control standard in the following ranges:
z
0.450 ... 0.500 cm
-1
(e.g. TetraCon, nominal cell constant 0.475)
z
0.800 ... 1.200 cm
-1
(cells with a cell constant of approx. 1)
Besides, you can set the cell constant manually in the following ranges:
z
0.090 ... 0.110 cm
-1
z
0.250 ... 2.500 cm
-1
The fixed cell constant, 0.010 cm
-1
can also be selected. It is not nec-
essary to calibrate or adjust it.
Cell constants outside the above mentioned ranges cannot be calibrat-
ed.
Calibration interval
The interval for the determination of the cell constant (Int 3) is set to 180
days in the factory. You can select the interval in the range of 1 ... 999
days.
AutoRead
The calibration procedure automatically activates the
AutoRead
func-
tion.
Displaying the
adjusted
cell constant
Each time the instrument is switched on, the adjusted cell constant and
temperature compensation are shown on the display for a short time
(see section 4.1 S
WITCHING
ON
THE
MEASURING
INSTRUMENT
). In order to
view the data, switch the measuring instrument off and switch it on
again.
