Wednesday, December 19, 2018

The basic principle of conductometry

Conductivity measurement is one of the most important needs of today's laboratories. Laboratories that are involved with water and wastewater analysis, pharmaceutical manufacturing, bulk drug manufacturing, biotechnology, environmental analysis, soil analysis, metal processing, food processing, and  Agro manufacturing, etc. In that various characteristic like quality control, pollution control, process monitoring and managing require performing conductivity measurement regularly.
Conductivity is the measure of the ability of the material to carry out electrical current. Siemens “g” is the conductance basic unit and which is reciprocal of resistance and that measured in ohms. Conductivity measurement of the sample solution provides the degree of electrical conductivity in the definite quantity of the solution. The electrical conductivity of the solution is similar to the number of ions available in it and therefore the conductivity measurement of a solution will give a reading of the solution.
The principle by which the system measures the conductivity is simple. There are two conductivity plates are situated in the sample and potentially apply to them (usually ac voltage) and after that, the current is measured. By voltage and current values, conductivity can be determined. Constant specific conductivity can be determined to multiply the conductivity by electrode cell. This constant is calculated by the formula as below,

Gt = Gt cal { 1 + a (t - t cal) }
Where Gt is Conductivity at any temperature in °C
G tcal is Conductivity at calibration temperature in °C
a is the Temperature coefficient of the solution
t cal is calibration temperature.

By considering the temperature coefficient of the sample with the modern conductivity meter, this change can be remunerated automatically or manually. For accurate conduct measurement, automatic temperature compensation (ATC) with different temperature sensor is required and the standard and sample must be measured at the same temperature. Conductivity is also used for determining the total dissolved solids (TDS) and salinity.


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