Conductivity is the ability of a solution to conduct a large amount of current. The conductivity of water is related to the amount of inorganic acid, alkali and salt. When their concentration is low, the conductivity increases with the increase of concentration. Therefore, this index is often used to estimate the total concentration or salt content of ions in water.
The conductance (g) is the reciprocal of the resistance (r). Therefore, by inserting two electrodes (usually platinum electrode or platinum black electrode) into the solution, the resistance R between the two electrodes can be measured. According to ohm's law, when the temperature is constant, this resistance value is directly proportional to the electrode spacing L(cm) and inversely proportional to the electrode cross-sectional area A(cm2), that is, R=ρ×(L/A) where ρ is the resistivity, that is, the resistance of a conductor with a length of 1cm and a cross-sectional area of 1cm2, and its size depends on the properties of the substance.
According to the above formula, the conductance (g) of a conductor can be expressed as the following formula: g =1/r = (1/ρ) × (a/l) = k× (1/j), where K= 1/ρ is called conductivity.
The conductivity of electrolyte solution refers to the conductivity when the solution of 1cm3 is filled between two parallel electrodes with the electrode spacing of 1cm. It can be seen from the above formula that when the electrode constant (j) is known, the conductivity can be obtained when measuring the resistance (r) or conductivity (g) of the solution.
Mettler toledo InPro 7 100 series conductivity sensors provide digital signal models. Using intelligent sensor management (ISM) technology, the conductivity value is directly calculated inside the sensor and sent to the transmitter as a digital signal. This will be more accurate than analog signal sensors. In addition, the sensor can store its own calibration data, and can be calibrated quickly and accurately at any suitable position far away from the process.