Vernier Software and Technology
Vernier Software & Technology
Tech Info Library

How is the temperature compensation calculated on my conductivity probe (CON-BTA)?

The Conductivity Probe, order code CON-BTA, $99 is automatically temperature compensated between temperatures of 5 and 35°C. Note that the temperature of a solution is being read by a thermistor that extends into the space between the graphite electrodes. Readings are automatically referenced to a conductivity value at 25°C; therefore, the Conductivity Probe will give the same conductivity reading in a solution that is at 15°C as it would if the same solution were warmed to 25°C. This means you can calibrate your probe in the lab, and then use these stored calibrations to take readings in colder (or warmer) water in a lake or stream. If the probe were not temperature compensated, you would notice a change in the conductivity reading as temperature changed, even though the actual ion concentration did not change. If the solution temperature is higher than 35°C. The probe will see it as a 35°C solution and compensate to that max 35°C temperature.

This temperature compensation is calculated by applying an industry standard 2% to the conductivity value for every degree away from 25°C the temperature reads.

Some instructors may want to remove this temperature compensation from their measurements to do a study of how temperature alters conductivity. To do this, you will have to make sure you are collecting temperature at the same time as conducting with a temperature probe. Once you are finished collecting data, set up a calculated column with the following expression:
Uncompensated conductivity = compensated conductivity / (1 + ((25 - Temperature in °C) * 2 / 100))

We also offer the Platinum-Cell Conductivity Probe, order code CONPT-BTA, $149 and Go Direct® Conductivity Probe, order code GDX-CON, $99, both of which have a setting that allows the user to turn on and off the temperature compensation feature.

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