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Capacity measuring transducer
Capacity transducers, sensors




  
   In every transducer, a transforming element is based on certain physical principle which is related to electric descriptions of device so, that the change of measurand entails the change of these descriptions. Changes in electric descriptions are created by an electric signal, depending on a measurand.
   Although there are for sale thousands of measuring transducers at the market, principles actions which they are based on, exists relatively a bit. It is therefore possible to consider these principles in detail enough. All basic principles used in transducers  can be united in categories which are described below.


Capacity transducers
   Capacity transforming elements convert the changes of measurand into the changes of capacity. A condenser is formed from two plastins, divided by the layer of dielectric, and his capacity is determined from next expression:

                        C = εоεS/x

Where   εо - electric permanent, ε  is an inductivity  of dielectric;
S is an area of surface of every plate; is distance between plates.

                                          Fig. 1.  Capacity measuring transducer
 
   It ensues from this correlation, that a capacity depends on an inductivity, area of surface of plastins and distance
between them (fig. 1).
   The capacity of such transducers is usually measured as follows:
1) by means of bridge chart of alternating current, in which a transducers forms one shoulder of bridge;
2) by means of multivibrator in which a condenser in a chain determines frequency of vibrations.

SENSORS OF PHYSICAL PARAMETERS