YSI 3200 - Manual (Page 49)

Principles of Operation Section 8
CELL CONSTANT CALCULATION
YSI 3200 and 3400 Series conductivity cells are calibrated to ± 1% of nominal by means of a
YSI transfer standard traceable to OIML Recommendation 56 and NIST.
Anytime the condition of the conductivity cell changes, it is possible that the cell constant has
also changed. Therefore, you should calibrate your system regularly (See section 3.2 Cell
Calibration, Cal K). If you want to manually calculate your cell constant, measure the
conductance of a standard solution and compare with the theoretical conductivity of the solution.
The formula for determining the cell constant is:
K =
k
ℵ
where K = cell constant in cgs metric units (cm
-1
)
k = measured conductance in
µ mho
ℵ
= theoretical conductivity in
µ mho/cm
The measured conductance (k) and conductivity (
ℵ) must either be determined at the same
temperature or corrected to the same temperature for the equation to be valid. One main reason
for cell constant calibration is to increase overall system accuracy.
CONDUCTIVITY CELL CALIBRATION - SOME THINGS TO REMEMBER
1. Rinse the cell and solution container with some calibrator solution before calibration.
2. Prevent contamination of the solution.
3. Minimize evaporation of the solution.
4. Use adequate sample volume.
5. Purge all air from the cell.
6. Allow adequate time for temperature equilibration.
7. Stir the solution slowly.
8. Know the solution temperature accurately; a 1º C temperature error is approximately a
2% error in conductivity.
9. Insure sound electrical connection between the cell and the instrument.
YSI Incorporated Model 3200 45