Conductivity Measurement and Testing
Conductivity testing in the lab and in the field
Measuring conductivity is essential to your workflow, as it measures the ability to pass electrical flow formed by the concentration of ions. We offer an extensive line of meters, probes, standards, and measurement accessories designed to make your conductivity measurements accurate and reliable.
What is conductivity and why should it be measured?
The conductivity of water depends on the concentration of ions and temperature.
- We use conductivity measurements to determine the amount of dissolved ions present in a water sample, which serves as a measure of water quality.
- Although conductivity measurements are generally simple, not accounting for temperature will greatly affect the validity of the data generated. Applying temperature compensation is a way to account for temperature effects, and helps ensure the reliability and accuracy of your measurements. Temperature compensation uses the raw conductivity and temperature readings of the sample and applies a coefficient or algorithm to calculate and report the conductivity value of the sample at the selected reference temperature.
How to accurately measure conductivity
Although conductivity measurements are generally simple and easy to take, mistakes can still affect the validity of the data generated. By understanding and avoiding the most common measurement mistakes, you can help ensure you are on the path to accurate and reproducible readings.
- Use a suitable conductivity sensor. Sample composition, location (i.e. need for durability in the field), and the purity of the water sample can all influence the type of conductivity sensor you choose. Select the right conductivity probe.
Learn more ›
- Understand and anticipate the effects of temperature. Conductivity measurements are strongly affected by the temperature of the sample. Learn more about temperature sensitivity of conductivity ›
- Accurately use the temperature compensation (TC) function. Temperature compensation (TC) will calculate and display the conductivity at the chosen reference temperature. If TC is off, the displayed value is the actual conductivity at that temperature.
- Carefully set the temperature compensation settings. Whether to apply a TC or not, or what type of TC selected, can affect the accuracy of your readings.
- Take a conductivity reading only after temperature equilibrium is achieved. Conductivity is temperature-dependent, so time must be allowed for the conductivity sensor to equilibrate to the same temperature as the sample.
- Minimize the use of elaborate multi-point calibrations. According to ASTM, a one-point calibration of the cell constant at a representative conductivity is sufficient for accurate conductivity readings. If the samples cover a large range of conductivity levels, one or more points can be made.
- Use additional care and caution when handling low-level conductivity samples. The stability and purity of the sample and how it is handled can affect the accuracy of the sample reading. Low-level samples can be easily affected by contamination, CO2 absorption, and degassing.
- Avoid setting calibration standards that are too low. Low-level standards are prone to contamination and difficult to use successfully. Tighter accuracy can be achieved by calibrating at 100 µS/cm or above.
- Follow storage and maintenance guidelines for your conductivity sensor. Improper long-term and short-term storage of conductivity sensors can change the surface and adversely affect their performance.
- Understand how to calculate Total Dissolved Solids (TDS) factor. Conductivity readings can be used to determine an estimate of the TDS in a sample by applying a TDS factor through the meter setup. This TDS value is an estimate, since the true TDS is determined by gravimetric testing.
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