Xylem Multi 3420 - Manual (Page 85)

Multi 3420 Operation
85 ba75864e11 02/2011
4.10.5 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 recom-
mend: 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
4.10.6). Subsequently, you can transmit the displayed calibration data
to the interface, e. g. to a PC, with the key.
Note
The calibration record is automatically transmitted to the interface after
calibrating.
Sample record
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.
Multi 3420
Ser. no. 09250023
CALIBRATION Cond
Calibration date
31.07.2009 16:13:33
TetraCon 925
Ser. no. 09250033
Cell constant 0.476 1/cm 25.0 °C
Sensor
+++
Display Calibration
record Cell constant [cm
-1
]
+++ Within the range
0.450 ... 0.500 cm
-1