Water Quality
Parameters
Conductivity
Conductivity is a parameter used to measure the ionic concentration and activity of a solution. The more salt, acid or alkali in a solution, the greater its conductivity.

The unit of conductivity is S/m, often also S/cm. The scale for aqueous solutions begins with pure water at a conductivity of 0.05 µS/cm (77 °F /25°C).

Naturally occurring waters such as drinking water or surface water have a conductivity in the range 100 – 1000 µS/cm. At the upper end of the chart some acids and alcalines can be found.

Conductivity measurements are used for applications such as in the production
of ultrapure water or determining the salinity of sea water.

Conductivity is measured by making a measurement of the electrical resistance.
The simplest kind of measuring cell used consists of two similar electrodes. An
alternating voltage applied to one of the electrodes causes the ions in the solution
to migrate towards the electrodes. 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 taken the cell data into account – the conductivity.


WTW's InoLab Cond 720 Laboratory Meter