Conductivity Measurement: Process Conductivity Analyzers
Online conductivity measurement in boiler, cooling, treatment and ultrapure water lines: conductivity analyzers, transmitters and resistivity solutions.
Measurement methods: Conductometric Conductivity
What is conductivity and why is it measured?
Conductivity is the ability of water to conduct electricity, and it is a fast, general indicator of dissolved ionic substances. The conductivity of pure water is very low; it rises as the amount of ions increases. It is therefore one of the first parameters checked for purity and treatment performance in process waters. In boiler feedwater and condensate, a rise in conductivity gives early warning of problems such as condenser leakage or resin exhaustion; it is used for blowdown control in boiler water, for tracking cycles of concentration in cooling towers and for quality monitoring at reverse osmosis and ion exchanger outlets.
Where is conductivity measured?
- Power plants: In feedwater, boiler water, condensate and steam samples.
- Water preparation systems: At reverse osmosis, ion exchanger and demineralization outlets.
- Cooling and wastewater lines: In blowdown control and discharge monitoring.
- Ultrapure water applications: As conductivity or resistivity.
The method used for conductivity
In conductometric measurement, the sensor measures the sample's conductivity using an alternating voltage applied between two electrodes, and converts it to a reference temperature with temperature compensation. Contacting electrode sensors are used in clean, low-conductivity waters, and toroidal (electrodeless) sensors in fouling, high-conductivity streams. For ultrapure waters, sensor kits with special cell constants and resistivity display options are available.
Choosing a conductivity analyzer
- Sample conductivity range: ultrapure, low or high level
- Choice of contacting or toroidal sensor
- Resin column and degassing if cation conductivity (degassed) is required
- Temperature compensation and calibration method
Conductivity measurement with Tetra
Tetra supplies Thermo Orion process analyzers in Türkiye and provides installation, supply of reagents and consumables, commissioning, calibration and service.
Frequently asked questions
What units is conductivity expressed in?
In process waters, conductivity is generally given in µS/cm, and in high-conductivity solutions in mS/cm. In ultrapure waters, its inverse, resistivity (MΩ·cm), is used. Theoretically, the conductivity of pure water at 25 °C is approximately 0.055 µS/cm and its resistivity is 18.2 MΩ·cm.
How is the cell constant selected for a conductivity sensor?
The cell constant is selected according to the conductivity range to be measured: sensors with a small cell constant (for example 0.01 or 0.1 cm⁻¹) are used in ultrapure and low-conductivity waters, and those with a large cell constant at higher conductivities. A wrong cell constant reduces accuracy at the lower or upper part of the range. Toroidal sensors are more suitable for high-conductivity, fouling streams.
Why does temperature compensation matter in conductivity measurement?
Conductivity varies markedly with temperature; natural waters show an increase of around 2 percent per degree. Values are therefore generally converted to a reference temperature of 25 °C for reporting. Because this relationship is not linear in ultrapure waters, non-linear compensation algorithms designed for these applications should be used.
How is a conductivity analyzer calibrated?
In the medium and high conductivity range, calibration is performed with standard conductivity solutions of known value. At very low conductivity, standard solutions are easily affected by CO₂ in the air, so comparison with a calibrated reference sensor in the same sample stream is preferred. For sensors with a certified cell constant, calibration mostly takes the form of verification.
Products measuring this parameter
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