OVERVIEW
OVERVIEWPotentiometerLVDTResolver
Rotational PotentiometerLinear Potentiometer
LVDT (Linear Variable Differential Transducer or
Transformer)They are used to translate linear motion into electric
signals.They have high resolution, high accuracy and good stability
to make them ideal device for short displacement measurements.
Movable coreMovable corePrimary coilSecondary coilP Primary
winding S Secondary winding
PSSP - Primary CoilS , S - Secondary CoilsAC SourceThe two
secondary coils are placed equal distance from primary coil.Two
secondary coils are connected in series opposition i.e. Net Emf =
0.
Working of LVDT
There are three positions of core based on which the LVDT
works.This also determines the magnitude and direction of emf
induced.
Core at centerCore at right cornerCore at left corner
Magnitude of E indicates the distance moved while polarity or
phase indicates the direction.
ResolverAresolveris used for measuring degrees of
rotation.Operating principle is that a charged rotating shaft will
induce voltage on stationary coils.
DescriptionAresolveris a rotary transformer where the magnitude
of the energy through the resolver windings varies sinusoidal as
the shaft rotates. A resolver control transmitter has one primary
winding i.e. the reference winding (rotor), and two secondary
windings, the SIN and COS windings (stator).Since the rotary
transformer then passes the voltage off to the secondary side of
the transformer, no brushes or rings are needed.The SIN and COS
windings are mounted 90 from each other in relation to the
shaft.
Working of a Resolver
The primary winding of the transformer, fixed to the stator, is
excited by a sinusoidal electric current, which byelectromagnetic
induction induces current in the rotor.This current then flows
through the other winding on the rotor, in turn inducing current in
its secondary windings, the two-phase windings back on the stator.
The two two-phase windings, fixed at right (90) angles to each
other on the stator, produce a sine and cosine feedback current.
The relative magnitudes of the two-phase voltages are measured and
used to determine the angle of the rotor relative to the stator.
Upon one full revolution, the feedback signals repeat their
waveforms.
