Xylem HandyLab 200 - Manual (Page 32)

Operation HandyLab 200
32 ba77063e01 03/2014
4.4.5 Determining the cell constant (calibration in
control standard)
Why determine the cell
constant?
Aging slightly changes the cell constant, e.g. due to coatings. As a
result, an inexact measured value is displayed. The original character-
istics of the cell can often be restored by cleaning the cell. Calibration
determines the current value of the cell constant and stores this value
in the meter.
Thus, you should calibrate at regular intervals (we recommend: every
6 months).
Procedure You can determine the actual cell constant of the conductivity measur-
ing cell by calibrating with the control standard in the following ranges:
The cell constant is determined in the control standard, 0.01 mol/l KCl.
Cell constants outside the ranges quoted above cannot be calibrated.
In the default condition, the calibrated cell constant of the meter is set
to 0.475 cm
-1
(conductivity sensor LF413T).
Stability control
(AutoRead)
In calibration, the Stability control function (AutoRead) is automatically
activated.
Display calibration data You can have the data of the last calibration displayed (see section
4.4.6).
Calibration evaluation After calibration, the meter automatically evaluates the current status of
the calibration. The evaluation appears on the display and in the cali-
bration record.
Determining the cell
constant
For this calibration procedure, the Measuring cell setting must be set to
cal in the Measurement menu. Proceed as follows to determine the cell
constant:
1 Connect a conductivity measuring cell to the measuring instru-
ment.
2 In the measured value display, select the conductivity parame-
ter with .
3 Start the calibration with .
The cell constant that was calibrated last is displayed.