wtw Multi 3430, Operating Manual

Page: 70 / 102

Operation Multi 3430
70 ba75865e02 12/2009
4.8.5 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 IDS conductivity sen-
sor cell by calibrating with the control standard in the following range:
z
0.450 ... 0.500 cm
-1
(e.g. TetraCon 925, nominal cell constant 0.475)
The cell constant is determined in the control standard, 0.01 mol/l KCl.
In the delivery condition, the calibrated cell constant of the IDS sensor
is set to 0.475 cm
-1
(conductivity measuring cell, TetraCon 925).
Stability control
(AutoRead)
In calibration, the Stability control function (AutoRead) is automatically
activated.
Display calibration data
and output to interface
You can have the data of the last calibration displayed (see section
4.8.6). Subsequently, you can transmit the displayed calibration 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:
Calibration evaluation After the calibration, the meter automatically evaluates the current sta-
tus of the calibration. The evaluation appears on the display and in the
calibration record.
31.07.2009 16:55:12
Multi 3430
Ser. no. 09507128
CALIBRATION Cond
TetraCon 925
Ser. no. B211371282
31.07.2009 16:13:33
Cell constant 0.836 1/cm 25.0 °C
Sensor
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