Do you know What is Conductivity?
Conductivity is the ability of Solution to conduct electrical current.Ions in solution (e.g., dissolved salts or acids) carry electrical current.Ions that have lost electrons are charged positive, and ions that have gained electrons are negative. The more ions in a solution, and the more electrons being transferred, the more conductive a solution is . Conductivity is used to measure the volume of dissolved solids in a solution.
Now we will discuss different Measurement Techniques for conductivity,
First one is Electrode Conductivity.
Second is Inductive Conductivity.
In electrode conductivity we have two types,
Conductivity measurement with conductive 2 electrode sensors
Conductive probes feature two electrodes that are positioned opposite from each other. An alternating voltage is applied to the electrodes which generates a current in the medium. The intensity of the current depends on the number of the medium’s free anions and cations that move between the two electrodes. The more free anions and cations the liquid contains, the higher the electrical conductivity and the current flow. The conductivity unit is “Siemens per meter”.
Conductivity measurement with conductive 4-electrode sensors
A high ion concentration in the medium leads to a mutual repulsion of the ions and thus a reduction of the current – the so called polarization effect. This can influence the measuring accuracy of conductive probes. 4-electrode sensors have two electrodes that are currentless and therefore not affected by the polarization effect. They measure the potential difference in the medium. A connected transmitter uses the measured potential difference and current to calculate the conductivity value.
Now we will discuss
Conductivity measurement with inductive sensors
Electrodeless conductivity sensors use inductive coils. The inductive conductivity sensor consists of two coils which are incorporated next to one another in a polymer or ceramic body. These coils form current transformers. The sensor is designed so part of the liquid media forms a closed conductive current path passing through the coils. An oscillator generates an alternating magnetic field in the transmission coil, which induces a voltage in the medium. In liquids which conduct electricity, causes a current flow captured by the second coil (receiving coil), which is proportional to the conductivity of the sample solution.
In my next video I will discuss about how to calibrate conductivity transmitter using HART Communicator.