Two cores, 2 and 3, of an inductance pickup are rig id ly secured
to one section of the shaft being investigated. Secured to the
other section is pickup armature 4, which is arranged at equal
distances from cores 2 and 3 when the shaft is not loaded w ith
a torsion load. Twist of the shaft increases the air gap between
armature 4 and one of the cores and, at the same tim e, reduces
the gap between armature 4 and the other core. Electric current
is supplied to the coils through brushes 5 and slip rings 6.
Changes in the air gaps between armature 4 and cores 2 and 3
increase the reactance of one coil and reduce th at of the other.
The changes in reactance of the coils is used to determine the
relative displacement of armature 4 w ith respect to cores 2
and 3. This displacement is used to find the angle of twist of
the section of the shaft.
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