Conductivity

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Conductivity
Dr. Edgar Ballin
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Conductivity Measurement Principle
Goal of Conductivity Measurement

• monitor conductivity- hi-purity for boiler feed
  water,- break through detection heat
  exchangers membranes- pharmaceutical water USP

• calculate conductivity for a given temperature

• determine concentration

• determine salinity

• calculate membrane efficiency

• calculate pH-value via differential technique
  (high purity)

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Conductivity Measurement Principle
1 Resistivity Conductivity
1 Conductivity Resistivity
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Conductivity Measurement Principle
Conductivity 1 1 Siemens 1 Mho
OM OM 1 Ohm X 1 Meter
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Conductivity Measurement Principle
inductive principle
e.g. 100 Ohm
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Conductivity Measurement Principle
Conductivity (?) Conductance (G) X Cell
Constant (c)
A
Cell Constant c c Length / Area
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Conductivity Measurement Principle
Conductivity (?) Conductance (G) X Cell
Constant (c)
1 cm (length) 1 cm2 (area) 1 Cell Constant
0.1 cm (length) 1 cm2 (area) 0.1 Cell
Constant
Cell Constant c c Length / Area
The bottom line High Conductivity requires High
Cell Constant Low Conductivity requires Low Cell
Constant
Cell Constant c c Length / Area
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Conductivity Measurement Principle
Cell constant Optimum Conductivity Range
(µS/cm) 0.1 0.5 to 400 1.0 10 to
2000 10.0 1000 to 200,000
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Conductivity Measurement Principle, 2 Electrode
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Conductivity Measurement Principle, 2 Electrode
electrical potential
Help alternating anode /cathode
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Conductivity Measurement Principle
SensoCheckâ
polarization
u
meas.
0
t
-u
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Conductivity Measurement Principle 4 Electrode
polarization
polarization effects are eliminated by separating
current and voltage path
voltage path
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Conductivity Measurement Principle Inductive
(Toroidal)
inductive principle
e.g. 100 Ohm
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Conductivity Measurement Electrodes
Conductivity probes
GSX
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Conductivity Measurement Installation
Requirements
C a l i b r a t i o n r e q u i r e d
metal
correct
too low
too high
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Conductivity for Determination of Concentrations
Determination of concentration via
conductivityis possible for pure aqueous
solutions of

• NaCl (Salt)
• HCl (Hydrochloric Acid)
• NaOH (Sodium Hydroxide Caustic)
• H2SO4 (Sulfuric Acid)
• HNO3 (Nitric Acid)

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Conductivity for Determination of Concentrations
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Conductivity for Determination of Concentrations
Isotherms of Conductivity over concentration
(here Sulfuric Acid)
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Conductivity Temperature Compensation
Temperature compensation for conductivity
measurement Advantage- comparable
values Problem- very important reason for
wrong determination - temperature coefficient is
mostly unknown - the conductivity is very often a
non-linear function of the temperature -
dependance of the temperature function on the
concentration itself
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Conductivity Temperature Compensation
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Conductivity Temperature Compensation
Further non - linear functions for Conductivity
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Protos Special Feature
Calculation of pH based on conductivity
measurement
conductivitymeasurement I
conductivitymeasurement II
ion exchanger
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Protos Special Feature
Calculation of pH based on the conductivity
measurement