wtw LF 170 - Checking;Setting the Cell Constant

LF 170 Operation
107
ba54104e09 11/2010
4.7 Checking/Setting the cell constant
Normally the cell constant specified by the manufacturer is given in the
delivery documentation or the relevant labeling on the sensor.
Note
For conductivity measuring cells with the cell constants, 1 cm
-1
,
0.1 cm
-1
and 0.01 cm
-1
(see configuration, setting CIn), the cell
constant cannot be changed.
Why check/set the cell
constant?
Over time the characteristics of the cell change slightly, e.g. due to
sediments. This results in an inexact measured value being displayed.
The original characteristics of the cell can often be restored just by
cleaning the cell. In the process described below the current cell
constant is determined, stored in the monitor and used for all future
measurements.
Setting range The setting range for the cell constant depends on the sensor type (see
configuration, setting CIn):
Process In order to determine the cell constant, the conductivity measuring cell
is immersed in a conductivity standard (0.01 mol/l potassium chloride
solution). The reference temperature is automatically set to 25 °C. At
this temperature the control standard has a conductivity of 1413 µS/cm.
If there is any deviation, the measured value can be matched to the set
value by varying the cell constant.
Note
Only immerse the conductivity measuring cell in the control standard
when it is in a clean and virtually dry condition. Impurities or water alter
the conductivity of the control standard. Only use the control standard
once.
Sensor type Setting range
700 0.090 ... 1.500 cm
-1
600 0.090 ... 1.500 cm
-1
300 0.090 ... 1.500 cm
-1
10 5.00 ... 15.00 cm
-1
1
(no setting possible)=1
=01
uAr 0.090 ... 1.500 cm
-1