Conductivity measurement: Basics and overview on measurement technique and application examples
Conductivity is a sum parameter of the level of ion concentration of a solution. The more salts, acids or bases are dissociated, the higher the conductivity.
The unit for conductivity is S/m, in many cases also S/cm.
The scale for aqueous solutions starts at a conductivity of 0.05 µS/cm (at 77 °F/25 °C) for ultrapure water. The conductivity of natural waters, such as drinking water or surface water is typically in the range of 100 - 1000 µS/cm. The upper end of the scale is reached by some acids and alkalis.
Conductivity measurements are used for applications such as monitoring of algea, qualitiy control of ultrapure water or to determine the salinity of saltwater.
Conductivity is measured by making an electrochemical measurement of the conductance. The simplest kind of measuring cell used consists of two similar electrodes. An alternating voltage applied to the electrodes will be adjusted to the corresponding measuring range and provides a measurement without interfering polarization effects. The more Ions in the solution, the greater the current which flows between the electrodes. The instrument measures the current and uses Ohm's law to calculate first the conductance of the solution and then - by taking the cell data into account - the conductivity.
Conductivity measuring technology by WTW
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