Manual

12
The Digital Conductometer CG 855 can make
– conductivity measurements ranging from 0,1 S · cm
-1
... 19,99 mS · cm
-1
and
– temperature measurement from – 199,9 ... 199,9 °C.
This unit also incorporates a device for coating the measuring cells with platinum black.
1 Commencing operation
Important: Before connecting-up and switching-on, make sure that the nominal operating voltage of the
unit agrees with the actual mains voltage. The nominal operating voltage is stated on the type
specification plate.
Connect the unit to the mains (see Fig. 2, Pos. 5; a mains cable is provided with the unit).
Connect the conductivity measuring cell to the socket on the rear of the unit (Fig. 2, Pos. 1, "Kombizelle"
(Combicell) or "Zelle" (Cell). Measuring cells with constants ranging from K = 0.75 ... 1.25 cm
-1
can be
used. Connect a temperature sensor (Resistance Thermometer Pt 1000) for conductivity measurements
with automatic temperature compensation or for direct temperature measurements (see Fig. 2, Pos. 2).
When using a Combicell for conductivity and temperature, e.g. Type No. LF 1100 T, make the connection
optionally to the moisture-proof 4-pole SCHOTT-GERÄTE socket or to the 4 mm sockets using 4 banana
plugs (see Fig. 2, Pos. 1 and 2, "Zelle" (Cell) and "Pt 1000").
Switch-on at the mains switch (see Fig. 2, Pos. 5) and set the "FUNKTION" (FUNCTION) switch to "abs",
"man" or "auto" (see Fig. 1, Pos. 4), depending on the kind of temperature compensation desired.
2 Measuring the electrical conductivity
The Digital Conductometer CG 855 has three conductivity measuring ranges and one temperature
measuring range. (The specifications for the conductivity measuring ranges are based on the measuring
cell constant K = 1.0 cm
-1
.)
Setting of the measuring
range selector switch
Measuring Range (1 digit =)
200 S/cm (kappa): 0.1 ... 199.9 S · cm
-1
(0.1 S · cm
-1)
2000 S/cm : 1 ... 1999 S · cm
-1 (1
S · cm
-1)
20 mS/cm
: 0.01 ... 19.99
mS · cm
-1 (0.01
mS · cm
-1)
Temperature °C T: –199.9 ... 199.9 °C
(0.1 K)
Set the control knob "KONSTANTE" (CONSTANT) (see Fig. 1, Pos. 5) to the actual measuring cell
constant (cell factor). The value is stated on the conductivity measuring cell. The Digital Conductometer
CG 855 can be matched to any cell factor in the continuous range from 0.75 ... 1.25 cm
-1
. If the
measuring cell constant is unknown, dip the measuring cell with integrated temperature sensor
(combination cell with resistance thermometer Pt 1000) in 0.1 mol/l KCl solution and then bring the
function switch "FUNKTION" in setting "auto". When the reading has become steady, turn the cell
constant control knob to give the reading 12.88 mS·cm
-1
in the 20 mS/cm measuring range. The unit is
therewith matched to the measuring cell. The actual measuring cell constant can be read off as the setting
of the control knob.
Set the measuring range selector switch (Fig. 1, Pos. 6) to the range in which the conductivity is expected
to lie, e.g. "2000 S/cm".