Xylem handylab LF 12 - Manual (Page 22)

Operation handylab LF 12
22 ba75367e04 01/2011
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 characteristics of
the cell can often be restored by cleaning the cell. Calibration 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 measuring cell
by calibrating with the control standard in the following ranges:
z 0.450 ... 0.500 cm -1
z 0.800 ... 1.200 cm -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 necessary
to calibrate or adjust it.
Cell constants outside the above mentioned ranges cannot be calibrated.
Printing the
calibration
record
The calibration protocol contains the calibration data of the current calibration.
You can transmit the calibration protocol to a printer via the serial interface
(see page 39).
Note
You can automatically print a calibration protocol after the calibration. To do
so, connect a printer to the interface according to section 4.5.3 before cali-
brating. After a valid calibration, the record is printed.
Sample printout:
Calibration
evaluation
After the calibration, the measuring instrument automatically evaluates the
current status of the calibration. The evaluation appears on the display.
CALIBRATION PROTOCOL
14.04.01 11:37
Device No.: 99990000
Calibration Conductivity
Cal time: 14.04.01 / 11:37
Cal interval: 180d
Cal Std.: 0.01 mol/l KCL
40.0 °C
Conduct./Tref25: 1413µS/cm
Cell Const : 0.478 1/cm
Probe : +++