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Capacative Measuring Technology

Capacative Measuring Technology
Capacative Measuring Technology
Every electrically charged material is surrounded by an electric field.

Electric field lines from positive to negative are formed between materials with different charges.
Two differently charged metal plates isolated from one another form a condenser.


Principles of the Condenser
Principles of the Condenser
The principle of capacitive level measurement is based on the change in the capacity of a condenser caused by a change in the level. The capacity of a condenser is determined by means of 3 factors:
Gap between electrode surfaces (d)
Size of electrode surfaces (A)
Dielectric between the electrodes (eI)
Electric field constant
8.854*10-12 C/(Vm)
Dielectric constant (medium)


Dielectric Constants
Dielectric Constants
Dolomite
Iron oxide
Grain
Broken glass
Coffee
Lime hydrate
Lime powder
Coal, raw
Powdered coal
Fodder concentrate
Flour
Nylon granulate
Quartz powder
Rice
Sand, dry
Washing powder
Air = 1
Alcohol
Petrol
Chloroform
Desmophen 5100
Desmodur 44 V
Deuterium
Liquid gases
- Chlorine
- Air -140C
- Butane
- Propane
Glycerine
Heating oil
Latex
Petroleum
Water


Electric Conductivity
Electric Conductivity
Non-conductive media
(hydrocarbons, solvents, petrols, oils)
Low-conductive media
(hydrocarbons with a higher water content, demineralised water)
The DK of the medium must not change through moisture, for example. Otherwise, the level can no longer be reliably measured.
The measuring flow not only depends on the DK, but also on the conductivity of the medium.
Conductive media
(aqueous solutions of salts, acids, alkalis, electrolytes, food, beverages)
A change in the DK and conductivity does not have any effect on capacity since the medium produces a short circuit with the container wall.


For more information: Endress+Hauser GmbH
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