1.2.4 Conductivity

The Levelogger LTC models provide the added feature of electrical conductivity measurement; they measure the actual conductivity at the current temperature. Conductivity measurement is particularly useful in monitoring saltwater intrusion, surface water infiltration and mixing, as well as being an indicator of certain pollutants and contaminant parameters. Conductivity is measured via a platinum 4-electrode sensor, which produces highly stable and consistent readings. Conductivity calibration is performed by using up to 4 specific calibration solution ranges, and the Calibration Wizard in the Levelogger Windows Software.

The Data Wizard allows you to convert conductivity readings to Specific Conductance (at 25ºC), Salinity expressed in Practical Salinity Units (PSU), or TDS. A Practical Salinity Unit (PSU) is a dimensionless descriptor for the Practical Salinity Scale (PSS). The PSS defines salinity as the ratio of a water sample's conductivity to that of a standard KCL solution. The Data Wizard uses the equation given in the UNESCO Technical Paper "Algorithms for computation of fundamental properties of seawater", to convert Conductivity readings to Salinity. For more information, see: Fofonoff, N. P. and R.C. Millard, Jr. Algorithms for computation of fundamental properties of seawater, UNESCO, Tech. Pap. Mar. Sci.,44. The Data Wizard uses the known equation "TDS=keEC" to convert Conductivity readings to TDS, where TDS is expressed in mg/L or ppm and EC is the electrical conductivity in μS/cm at 25˚C. Correlation factor ke is between 0.55 - 0.8. For more information, see: Al Dahaan, S.A.M., Al-Ansari, N. and Knutsson, S. (2016) Influence of Groundwater Hypothetical Salts on Electrical Conductivity Total Dissolved Solids. Engineering, 8, 823-830. http://dx.doi.org/10.4236/eng.2016.811074


For every degree change in temperature, there is approximately a 2% change in conductivity. To convert raw conductivity measurements to Specific Conductance measurements, you can use the following equation:

Specific Conductance = Conductivity / (1 + 0.02 * (temp(C) - 25))

You can also perform this calculation automatically using the Data Wizard.

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