YSI 3200 - Manual (Page 53)

Principles of Operation Section 8
SMALL SAMPLE MEASUREMENTS
It is not always possible to immerse the conductivity cell in a solution for measurements. If the
quantity of solution is not sufficient for a proper measurement with a dip cell, a sample must be
removed for assay. For this application, use the 3254 fill cell. This cell requires 5 ml of sample.
Alternatively, any 3200 or 3400 Series cell, except the 3418, may be inverted and used as a fill
cell.
The cell you use for small sample applications depends upon the
quantity of solution available and the conductivity of the solution.
The 3401 cell (K=1.0/cm) requires 15 ml, the 3256 and 3402 cells
(K=0.1/cm) require 12 ml, the 3253 and 3403 cells (K=1.0/cm)
require 3 ml, and the 3252 and 3417 cells (K=1.0/cm) require 1
ml of sample.
When a dip cell is used as a fill cell, the cell's vent hole is sealed
and the electrode chamber is inverted and filled with solution,
changing the cell constant (K). The cell will require calibration
after being configured as a fill cell.
CONDUCTIVITY SYSTEM ACCURACY CONSIDERATIONS
System accuracy for conductivity measurements is equal to the sum of the errors contributed by
the environment and the various components of the measurement setup. These include:
• Instrument accuracy
• Cell-constant accuracy
• Temperature measurement accuracy
Instrument Accuracy
YSI meters are very accurate; however, each instrument and range has its own accuracy statement
and therefore, must be accounted for in the overall accuracy determination.
Cell-Constant Accuracy
YSI cells are warranted to be accurate to within one percent, for more accurate work you should
calibrate the cell to determine the exact cell constant.
Temperature Accuracy
The solution temperature accuracy is the sum of the instrument accuracy plus the temperature
probe accuracy.
If the conductivity is to be expressed at 25
°C, some additional errors will be introduced either by
the instrument's temperature correction electronics or by the mathematics used for the conversion
to 25
°C.
YSI Incorporated Model 3200 49