Xylem Lab 960 - Manual (Page 26)

Operation Lab 960
26 ba75557e05 11/2009
4.4 Determining/setting up the cell constant [C]
Why determine/set up
the cell constant?
Due to aging, the cell constant slightly changes. As a result, an inexact
measured value is displayed. Calibration determines the current value
of the cell constant and stores this value in the instrument.
Thus, you should calibrate at regular intervals.
The calibration data is stored in the meter.
You can determine the cell constant of the conductivity measuring cell
in the ranges 0.450 ... 0.500 cm
-1
, 0.585 ... 0.715 cm
-1
or 0.800 ...
1.200 cm
-1
by calibrating in the 0.01 mol/l KCl control standard or set it
manually in the range 0.250 ... 2.500 cm
-1
or 0.090 ... 0.110 cm
-1
.
Besides, the fixed cell constant 0.010 cm
-1
can be selected.
Cleaning interval (Int.C) When the specified cleaning interval (Int.C) has expired, the Cln display
indicator appears after the meter has been switched on and reminds
you to clean the measuring cell. It is still possible to measure.
The cleaning interval (Int.C) is set to 180 days (d180) in the factory. You
can change the interval (see page 51).
Note
In order to maintain the high measurement accuracy of the measuring
system, clean the measuring cell and recalibrate after the cleaning
interval has expired.
4.4.1 Determining the cell constant (calibration)
Determining the cell
constant
(calibration in control
standard)
1 Press <CAL> repeatedly until CAL CELL is displayed.
L C L E
L A C