Delta OHM HD2205.2, Manual

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Choosing the cell constant
The cell constant K is a piece of information which characterizes the cell. It depends on its geome-
try and is expressed in cm
–1
. There is no cell capable of measuring the entire conductivity scale ac-
curately enough. Consequently, cells with different constants are used allowing good accuracy on
different scales. The cell with constant K = 1cm
–1
allows measurements from low conductivity up to
relatively high conductivity.
The theoretical measurement cell is made of two 1 cm
2
metallic plates separated one from the other
by 1 cm. This type of cell has a cell constant Kcell of 1 cm
–1
. In essence, the number, form, material
and dimensions of the plates in the cell are different from model to model, from manufacturer to
manufacturer.
The low constant K probes are preferably used for low conductivity values, the high constant ones
for high values.
The indicative measurement range is reported in the following diagram:
Automatic or manual temperature compensation for conductivity measurement
The conductivity measurement generally refers to a standard temperature, called reference tem-
perature , that is, the instrument proposes the conductivity you would get at the reference tempera-
ture. This temperature can be chosen within the range 0…50°C in the “ Conductivity Reference
Temperature ” menu item ( usually the values of 20°C or 25°C are used ).
The conductivity variation per each grade of temperature variation is a characteristic of the solution
and is indicated by the term "
temperature coefficient
α
T
": admissible values from 0.00 to
4.00%/°C, default value 2.00%/°C .
When a temperature sensor is present, the instrument automatically applies the temperature com-
pensation function, and proposes the measurement using the reference temperature according to the
coefficient
α
T
on the display.
In absence of a temperature probe or sensor, the display shows the MTC symbol under the meas-
ured temperature, to indicate the compensation temperature has been set manually.
The
MTC (Manual Compensation Temperature) symbol is included in the printouts; if the tempera-
ture probe is present, the ATC (Automatic Temperature Compensation) symbol is reported.
In MTC mode, in order to manually change the compensation temperature press F5=°C/°F once:
The indicated temperature value starts blinking. Select the desired temperature value by using the
and arrows, and confirm with ENTER. The display stops blinking, and the temperature dis-
played is used for compensation.
During manual compensation, to change the unit of measurement between °C and °F, it is necessary
to press the “
F5=°C/°F ” key twice .