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TERMINAL OBJECTIVE - h1011v4_72
Electrodynamometer Movement

Electrical Science Volume 4 of 4
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Test Instruments & Measuring Devices METER MOVEMENTS METER MOVEMENTS There are three basic meter movements utilized in electrical meters:  D’Arsonval, electrodynamometer, and the moving iron vane.   Some meter movements can be used for both AC or DC measurements, but in general, each meter movement is best suited for a particular type. EO 1.1 EXPLAIN the following meter movements: a. D’Arsonval b. Electrodynamometer c. Moving iron vane D’Arsonval Movement The most commonly used sensing mechanism used in DC ammeters, voltmeters, and ohm meters is a current-sensing device called a D’Arsonval meter movement (Figure 1).   The D’Arsonval movement is a DC moving coil-type movement in which an electromagnetic core is suspended between the poles of a permanent magnet. The    current    measured    is    directed Figure 1    D’Arsonval Meter Movement through the coils of the electromagnet so that the magnetic field produced by the  current  opposes  the  field  of  the permanent magnet and causes rotation of the core.   The core is restrained by springs so that the needle will deflect or  move  in  proportion  to  the  current intensity. The more current applied to the  core,  the  stronger  the  opposing field, and the larger the deflection, up to the limit of the current capacity of the    coil. When    the    current    is interrupted, the opposing field collapses, and the needle is returned to zero  by  the  restraining  springs.  The limit of the current that can be applied to  this  type  movement  is  usually  less than one milliampere. Rev. 0 Page 1 ES-14







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