How does the conductivity meter work?

Conductivity is the ability of a substance to carry an electric current and is the reciprocal of resistivity. In liquids, the reciprocal of the resistance—the conductance is often used to measure the conductivity. Water conductance is a very important indicator of water quality. It reflects the extent of electrolytes present in the water. According to the concentration of the electrolyte in the aqueous solution, the conductivity of the solution is also different. The solubility of the electrolyte in the dissolution was analyzed by measuring the conductivity of the solution. This is the basic analysis method of the conductivity meter.

The conductivity of the solution is related to the type of ion. The same concentration of electrolyte, their conductivity is not the same. The conductivity of the strong acid is usually the highest, followed by the strong base and the salt it produces with the strong acid, while the weak acid and weak base have the lowest conductivity. Therefore, through the measurement of the conductance of water, there is a preliminary understanding of the water quality. The reciprocal of the conductivity resistivity is called the conductivity L. In liquids, the reciprocal of the resistance—the conductance is often used to measure the conductivity. The formula for the conductance L is given by the following formula: L = l/R = S/l The unit of conductance is also referred to as Siemens. With S, because the S unit is too large. Millimeter Siemens is often used, micro Siemens unit 1S = 103mS = 106μS.

The conductivity of the conductivity meter equivalent conductivity liquid only shows the relationship between the conductivity of the solution and the geometry, and does not reflect the relationship between the solution concentration and the electrical properties. In order to be able to distinguish the conductive properties of various medium composition solutions, it is necessary to introduce the concentration relationship in the essentials of conductivity, which proposes the concept of equivalent conductance. The so-called equivalent conductance refers to the conductance of a solution containing 1 g equivalent of an electrolyte all placed between two plates with a distance of 1 cm, symbol "λ". Due to the introduction of the concept of concentration on the basis of conductivity. Therefore, the conductivity of various aqueous solutions is shown and compared. In water quality monitoring, the concentration of total inorganic salts dissolved in water can be determined by measuring the conductance of the solution.

Influence of Temperature on Conductance The resistance of a solution decreases with increasing temperature. That is, when the concentration of a solution is constant, its conductivity increases with increasing temperature, and its increase range is approximately 2%°C-1. In addition, the same kind of electrolyte, when the concentration is different, its temperature coefficient is not the same. At low concentrations, the relationship between the temperature of the conductivity is expressed by the following equation: L1 = L0 [1α(t-t0)β(t-t0)2] Since the value of the second term β(t-t0)2 is smaller Small, negligible. The relationship between conductivity and temperature at low temperatures can be expressed by the following approximate value L1=L0[1α(t-t0)], so temperature compensation must be added during actual measurement.