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download articleCapacative 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 -140°C - 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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