Conductivity Meter

Conductivity of any substance or solution is measured on the basis of Ohm’s law (V = I·R).

Conductance = 1/Resistance = 1/R = G

A different type of electrode is used in the conductivity meter compared to the pH meter

G is proportional to the area A of the faces or electrode, and inversely proportional to the distance between them. Resistance (R) is expressed in “ohms”; G is expressed in 1/ohms × cm; in modern instruments as “Siemens” (S).

Many factors influence the conductivity in your experiment; measuring conductivity of a salt solution: the number of ions, their concentration, their charge, their size, and ion mobility; therefore:

  • Conductivity is measured at a very low concentration (mM).
  • Usually, a standard curve of that specific salt solution is generated, before you determine the (unknown) concentration.