Conductivity tester is a high-end water quality management and automation that operates in higher temperature environment for medical multi-effect distilled water system, boiler bottom water, condensate water, heat exchange system, industrial thermal cleaning of mechanical parts, industrial circulating water, etc. Control developed an online water quality analysis instrument with a wide temperature range.
working principle
Conductivity is the ability of a solution to conduct current in numbers. The conductivity of water has a certain relationship with the amount of inorganic acids, alkalis and salts it contains. When their concentration is low, the conductivity increases with the increase of the concentration. Concentration or salt content.
Water quality hardness unit conversion
Hardness unit ppm German hardness French hardness British hardness
1ppm = 1.000ppm 0.0560 0.1 0.0702
1 German hardness = 17.847ppm 1 1.7847 1.2521
1 French hardness = 10.000ppm 0.5603 1 0.7015
1 British hardness = 14.286ppm 0.7987 1.4285 1
Electrical conductivity and water hardness
The conductivity of the aqueous solution is directly proportional to the dissolved solids concentration, and the higher the solids concentration, the greater the conductivity. The relationship between conductivity and dissolved solids concentration is approximately expressed as: 1.4 μS / cm = 1 ppm or 2 μS / cm = 1 ppm (CaCO3 per million units). The total hardness value of water can be obtained indirectly by using a conductivity meter or total solid dissolution meter. As mentioned above, for convenience of approximate conversion, 1μs / cm conductivity = 0.5ppm hardness
But need to pay attention:
(1) The hardness of water is measured indirectly by conductivity, the theoretical error is about 20-30ppm
(2) The conductivity of the solution determines the movement of the molecule, and temperature affects the movement of the molecule. In order to compare the measurement results, the test temperature is generally set to 20 ℃ or 25 ℃
(3) Using reagent detection can obtain more accurate water hardness value.
Soft water and hard water
Water is divided into soft water and hard water. Any water that does not contain or contains a small amount of calcium and magnesium ions is called soft water, otherwise it is called hard water. The hardness component of water, if it is caused by sodium bicarbonate or magnesium bicarbonate, is temporary hard water (boiling temporary hard water, decomposed sodium bicarbonate, precipitated by the formation of insoluble carbonate, and the water changes from hard water to soft water) ; If it is caused by sulfate or chloride containing calcium and magnesium, it is permanent hard water. According to the total hardness value of water, the total hardness of 0-30ppm is called soft water, the total hardness of more than 60ppm is called hard water, the high-quality drinking water does not exceed 25ppm, and the total hardness of high-quality soft water is less than 10ppm. In natural water, rainwater and snow water that are far away from the city without pollution are soft water; spring water, stream water, river water, and reservoir water are mostly temporary hard water, and some groundwater is high hardness water.
The common units for water hardness conversion are:
1mmol / L (1 / 2Ca2 +, 1 / 2Mg2 +) = 50 ppm (calculated as CaC03)
1mmol / L (1 / 2Ca2 +, 1 / 2Mg2 +) = 2.92 grain / gallon (grain / gallon)
lgrain / gallon (grain / gallon) = 17.1ppm (calculated as CaC03)
1m3 = 264gallon (US) (US gallon) = 22O ganon (UK) (UK gallon)
lkg = 2.2pounds (GBP)
1ppm = 1mg / L
TDS (total dissolved solids) is used to measure the total content of all ions in water, usually expressed in ppm.
In pure water manufacturing, electrical conductivity can also be used to indirectly express TDS.
The conductivity of a solution is equal to the sum of the conductivity of various ions in the solution.
The empirical formula is: half the conductivity in micro-Siemens is approximately equal to TDS (ppm)
Sometimes TDS is also expressed with other salts, such as CaCO3 (the coefficient is 0.66)
The conversion coefficient between TDS and conductivity can be adjusted between 0.4-1.0 to correspond to different types of electrolyte solutions.
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