Metrohm 820 IC Separation Center - Manual (Page 63)

3.1 819 IC Detector
819 IC Detector / 820 IC Separation Center
55
Ion Combination of polarity and temperature coeffi-
cient:
Anion polarity = +, temperature coeff. = 2.5
Cation polarity = –, temperature coeff. = 1.5
Custom
independent selection of
polarity
and
tem-
perature coeff.
Polarity Polarity of the analog output signal:
+ positive polarity (e.g. for anions)
– negative polarity (e.g. for cations)
Temperature coeff. Converts automatically the conductivity from
the operating temperature of the measuring cell
to the reference temperature of 20°C.
Selection:
1.5, 2.5 %/°C
Cell constant Cell constant of the conductivity cell in /cm.
Entry range: 13 ... 21 /cm
In ion chromatography, interest is normally cen-
tered only on relative changes in the conductiv-
ity and not on the absolute value. With the cell
constant of 16.7/cm set in the factory, the error
in the display of the absolute conductivity can
be up to ca.
± 10%.
If you wish to have a more accurate display of
the absolute conductivity, the cell constant
must be determined by means of a calibration
solution. To do this, pump a solution of known
conductivity through the IC system, observe the
display of the absolute conductivity and change
the cell constant until the displayed value
matches the actual value.
Thermostat Operating temperature of the conductivity cell
within in the detector block.
Selection:
25, 30, 35, 40, 45 °C and off
At constant ambient temperature the heating
built into the 819 IC Detector regulates the se-
lected measuring cell temperature to an accu-
racy of ± 0.01 °C and thus establishes the pre-
condition for highly sensitive determinations. It
normally takes 30...60 min after the instrument
has been switched on until this temperature
stability is attained.
Offset Offset of the zero point of the conductivity.
Selection: 0, 10, 50 %full-scale range