ELECTRICAL TYPE TORSIONMETER
sleeves are rigidly fixed to the shaft
having flanges at 90° to the shaft axis.
Twist causes relative displacement between
the flanges. Two cores are attached to one
flange and the iron piece to the other so
that relative movement between flange faces,
due to shaft twist, alters the air gap of
the differential transformer.
primary circuit is wound to give the same
polarity and the secondary circuits are in
opposition. With no torque the air gaps are
equal and the two secondary circuits are
equal and opposite, but when torque is
applied air gaps become unequal and a
current flows in the secondary circuit which
can be read on the galvanometer. An
identical unit is fitted in the indicator
box and by rotation of the handle the iron
piece can be moved until the air gaps in the
indicating unit are identical with those of
the shaft unit. This restores the electrical
equilibrium in the secondary circuit, as
opposed equal currents the galvanometer
reads zero, and the amount of movement at
the indicating box dial is indicative of the
angle of twist restoration required and
hence gives the angle of twist for the
length of shaft between the two flange faces
in the shaft unit.
application of the meter constant and rev /s
the shaft MW is thus determined.