wtw Multi 350i, Руководство по эксплуатации

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Multi 350i Operation
63
4.7.5 Determining the cell constant (calibration in the control
standard)
Why determine the cell
constant?
Aging slightly changes the cell constant, 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 deter-
mines the current value of the cell constant and stores this value in the
instrument.
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:
!
0.450 ... 0.500 cm
-1
(e.g. TetraCon 325, nominal cell constant 0.475)
!
0.800 ... 1.200 cm
-1
(cells with a cell constant of approx. 1)
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 delivery condition, the calibrated cell constant of the measuring
instruments is set to 0.475 cm
-1
(conductivity measuring cells,
TetraCon 325 and ConOx).
AutoRead The calibration procedure automatically activates the AutoRead func-
tion.
Display calibration data
and output to interface
You can have the data of the last calibration displayed (see
section 4.8.5). Subsequently, you can transmit the displayed calibra-
tion data to the interface, e. g. to a printer or PC, with the
<PRT> key.
Note
The calibration record is automatically transmitted to the interface after
calibrating.
Sample record:
3.11.03 07:14
CALIBRATION Cond
03.11.03 07:13:22
Multi 350i ser. no. 12345678
Cal. interval 14 d
Cell constant 0.975 1/cm 25.0 °C
Sensor +++