Process Analyzer

Conductivity Analyzer

What is Conductivity Analyzer?

Conductivity analyzer is a system that used for monitoring electric conductivity or salinity in terms of TDS and consists of two main parts:

  • The meter/regulator
  • The conductivity cell


Conductivity Analyzer Working Principle

The conductivity measurement is carried out using a cell with 2 or 4 electrodes featuring defined geometric dimensions, completely surrounded by the liquid, to which is applied an alternating voltage of suitable frequency to avoid polarization of the same caused by electrochemical effects. The electrode geometric defines the cell constant, normally referred to as “K”.

The electrical resistivity is the attitude of a material to resist to the passage of electric charges and same as the conductivity, it depends on the ionic concentration in solution. Conductivity and resistivity are determined from the voltage and current values according to Ohm’s Law:

conductivity analyzer working principle equation ohm's law

The measurement of TDS or concentration is carried out continuously by the conductivity measurement that is converted by the instrument into ppm or mg/l, multiplying the conductive value for the conversion coefficient. The conversion value of which is chosen is depending on the type of salt present in the solution. Therefore, the validity of the measure is closely related to the correctness of that coefficient.

TDS = Conductivity x Conversion Coefficient

Conductive Two Electrode Sensor

conductivity analyzer working principle two electrode

The measurement is based on the ability to conduct a current between two electrodes. The concentration of ions in the liquid are directly proportional to the conductance of the liquid.

Conductive Four Electrode Sensor

conductivity analyzer working principle four electrode

It keeps a constant current through two of the electrodes and let the drive voltage change. The drive voltage can be increased if fouling occurs in order to compensate the measurement. It minimizes the polarization of the electrodes and the measuring error for electrodes dirty.


Conductivity / TDS Controller