GE pH/C-900 Operating Instructions Manual page 41

Step
5
Calibrating the conductivity cell
Normally it is not necessary to adjust the cell constant as the flow cell is precalibrated
on delivery. Adjustment is only necessary when replacing the conductivity flow cell with
a flow cell whose cell constant is unknown. It is also recommended that the conductivity
flow cell is recalibrated after cleaning. When adjusting the cell constant from UNICORN
select SystemControl:System: Calibrate and then select CondCalib.
Note:
Step
1
2
3
4
5
Monitor pH/C-900 Operating Instructions 29-0549-25 AB
Action
Select sub menu Setup Cond Ref Temp, press OK.
Select the reference temperature to which the mea-
sured conductivity values will be converted (normally
20°C or 25°C), press OK.
The conductivity temperature compensation must not be used when adjusting
the cell constant. Set the Setup Cond temp comp to 0 (see Setting up conduc-
tivity temperature compensation, on page 40). The temperature sensor must
be calibrated before adjusting the cell constant (See Calibrating the temperature
sensor, on page 45)
Action
Prepare a calibration solution of 1.00 M NaCl, 58.44
g/l. Let the solution stand until it is at room tempera-
ture. This is important for exact measurements.
Fill the flow cell completely with the calibration solu-
tion, by pumping at least 15 ml through the cell with
a syringe.
Stop the flow and wait 15 minutes, until the temper-
ature is constant in the range 20°C to 30°C.
Read the conductivity value displayed and compare
it with the theoretical value from the graph, at the
temperature of the calibration solution. If the dis-
played value and the theoretical value correspond,
no further action is required. If the values differ, pro-
ceed with actions 5–8.
Select main menu Setup, press OK.
5 Operation
5.3 Setup menu
Display
Setup Cond Ref Temp
(22.3°C) 25. 0
Display
Setup
41