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Calibration
7/99 9782 Series Conductivity/Resistivity Analyzer/Controller - Operator’s Manual 8-5
8.4 Performing Calibration Trim
Introduction
For most applications entering the cal factor for each cell will achieve satisfactory system
performance. However, it is possible to perform a calibration trim procedure in which the
Analyzer/Controller and cell combination are used to measure a reference solution of known
conductivity; the reading of the Analyzer/Controller is adjusted to match.
The same procedure can be used to adjust the Analyzer/Controller’s reading while the cell is in
the process, if a reference instrument is used to determine the process conductivity. In this case,
the process fluid becomes the “reference solution”.
Materials and procedure
To perform calibration trim using a standard reference solution, follow the instructions in Table
8-3.
Materials required are:
• A reference solution of known conductivity near the point of interest, with the temperature
controlled (or measured and compensated) to within ± 1 °C. Conductivities of potassium
chloride solutions are provided in Table 8-2. Solutions must be prepared with high-purity
de-ionized, CO
2
-free water, and dried potassium chloride.
• A container for the reference solution, large enough to immerse the cell to measuring depth.
• De-ionized water to rinse the cell.
Table 8-2 Conductivity of Potassium Chloride Solutions at 25 °C
* M = Molarity; 1M = 74.555g potassium chloride per liter of solution
Concentration M* Conductivity (microsiemens
per cm)
0.001 147.0
0.005 717.8
0.01 1,413
0.02 2,767
0.05 6,668