Why does conductivity not always read correctly during calibration, but after calibration reads fine?

Document ID

Document ID TE6566

Published Date

Published Date 13/03/2017
Question
Why does conductivity not always read correctly during calibration, but after calibration reads fine?
Summary
When calibrating, the conductivity standard is not reading correctly
Answer

Conductivity, like other electrode measurements, is temperature dependent.  When a meter is completing calibration, it is reading the direct conductivity of the solution without applying any temperature compensation.  This is why a standard that may be labeled as a 1000 µS/cm at 25°C only reads 938 µS/cm at 22°C during calibration.  Settings in most meters allow you to define the level of temperature compensation for a particular sample type, such as 2.1% per °C, define whether the compensation is linear or curved, and define whether or not the compensation should be based on a sodium chloride or potassium chloride calibration.  Once this information is set in the meter and calibration is complete, the meter will temperature compensate any readings that are made by the probe.