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ec_theory

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ec_theory [31/03/2015 09:47]
pieter 		ec_theory [11/04/2018 11:50]
pieter
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 The units of measurement used to describe conductivity and resistivity are quite fundamental and are frequently misused. Once the units are known, various waters can be quantitatively described. The units of measurement used to describe conductivity and resistivity are quite fundamental and are frequently misused. Once the units are known, various waters can be quantitatively described.
  
-The basic unit of resistance is the familiar Ω (Ohm). Conductance is the reciprocal of resistance, and its basic unit is the Siemens (S). In discussions of bulk material, it is convenient to talk of its specific conductance, now commonly called its conductivity. This is the conductance as measured between the opposite faces of a 1 cm cube of the material. This measurement is taken in units of S/cm. The units //mS/cm// (milliSiemens per cm) and //µS/cm// (microSiemens per cm) are most commonly used to describe the conductivity of aqueous solutions. The corresponding terms for specific resistance (or resistivity) are //Ω.cm//, //MΩ.cm// and //kΩ.cm//.+The basic unit of resistance is Ohm. Conductance is the reciprocal of resistance and its basic unit is Siemens (S). In discussions of bulk material, it is convenient to talk of its specific conductance, now commonly called its conductivity. This is the conductance as measured between the opposite faces of a 1 cm cube of the material. This measurement is taken in units of S/cm. The units //mS/cm// (milliSiemens per cm) and //µS/cm// (microSiemens per cm) are most commonly used to describe the conductivity of aqueous solutions. The corresponding terms for specific resistance (or resistivity) are //Ω.cm//, //MΩ.cm// and //kΩ.cm//.
  
 +<WRAP center round box 60%>
 {{pictures/ec_curve.jpg?200|}}\\ {{pictures/ec_curve.jpg?200|}}\\
 //Conductivity// //Conductivity//
 +</WRAP>
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 Users of ultra pure water prefer to use the resistivity unit of //MΩ.cm//, because the measurement in this unit tend to spread the scale out in the range of interest. These same users frequently use //kΩ.cm// when dealing with less pure water such as tap water.  Users of ultra pure water prefer to use the resistivity unit of //MΩ.cm//, because the measurement in this unit tend to spread the scale out in the range of interest. These same users frequently use //kΩ.cm// when dealing with less pure water such as tap water. 
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 Since the conductivity of a solution varies with temperature, the measurements are always related to a reference temperature (most commonly used: 25°C). The __specific conductivity__ is expressed by the equation: Since the conductivity of a solution varies with temperature, the measurements are always related to a reference temperature (most commonly used: 25°C). The __specific conductivity__ is expressed by the equation:
  
 +<WRAP center round box 60%>
 **G = C x cc / (1 + a(t -tr))** **G = C x cc / (1 + a(t -tr))**
 +</WRAP>
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 in which: in which:
ec_theory.txt · Last modified: 11/04/2018 11:51 by pieter

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