Electronic Electrical Devices | Electronic Electrical Components
D'Arsonval Movement Meter Review
A commonly used sensing mechanism used in DC ammeters, voltmeters, and ohm meters
is a current-sensing device called a D’Arsonval meter movement. 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 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.
A common variation of the D’Arsonval movement is the Weston movement, which uses
essentially the same principle built to a more rugged construction by employing jeweled supports
for the core and employing a heavier winding in the electromagnet. Remember that the
D’Arsonval movement is a DC device and can only measure DC current or AC current rectified
to DC.
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