ELMETRON CX-401, Руководство пользователя

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15. CALIBRATION
A characteristic feature of every conductivity cell is its K constant. Before
displaying the reading the value is multiplied by the K constant value. The
value of the K constant depends on the size of the electrodes’ surface and the
distance between them. If the user keeps the cell clean, the K constant is not
changing. However, it is likely to change in case of contamination of the
surface of the electrodes.
Calibration consists in introducing the K constant value cell given by the
manufacturer (recommended) ) or with use of standard solution with known
conductivity – in order to determine the K constant. The meter enables
calibration in 5 standard solutions. In practice, it is sufficient to calibrate in one
solution of the value close to the anticipated measurement values.
The cell manufacturer precisely determines the K constant and using this
value will be the most reliable. In case of the user’s calibration it is
necessary to apply fresh, accurately prepared standard solution,
accurately thermostatic at 25
0
C. When these conditions are not kept, the
calibration will be burdened with error.
When using three cells, it is possible to store their characteristics under the ,
or symbol.
Entering the calibration mode irreversibly erases the K constant of the
cell stored under the chosen cell number.
After choosing the cell number, entering the calibration mode and
escaping it without making calibration, the stored K constant will be
erased and the K constant = 1 cm
-1
will be adopted. The erased
characteristic is signalised by the meter with red colour of the cell
number on the measuring screen.
15.1. Calibration without standard solution
The meter has a possibility of calibration without use of standard solution. In
case of such calibration it is necessary to know the K constant of the
conductivity cell. This value may be given by the manufacturer of the cell or
may be determined using CX-401 meter after calibration in standard solution.