2. The damping torque is produced by the
following methods:
1.Air Friction Damping
2.Fluid Friction Damping
3.Eddy Current Damping
3. • In this type of damping, a light vane or
vanes having considerable area is
attached to the moving system to develop
a frictional force opposing the motion by
reason of the air they displace.
4.
5. * Similar in action to air friction damping.
* Fluid with high viscosity is filled in the
chamber instead of air.
* Main drawback of this type of damping are
leaking of oil, the necessity to keep the meter
vertical and unsuitability in portable type
meter.
*Though in this method of damping is easy to be
used but it is not applied due to several
disadvantages, such as oil leakage, the necessity
of using the instruments always in vertical
position.
6. • Eddy current damping is the most efficient
form of damping.
• The essential components in this type of
damping are a permanent magnet; and a
light conducting disc usually of aluminium
7. • A thin disc of conducting, but non-magnetic material-usually
copper of aluminium is mounted on the spindle which
carries the pointer of the instrument.
• When the spindle rotates, the edge of the disc cuts through
the lines of force in the gap of a permanent magnet, with
eddy currents, and consequent damping are produced.
• An arrangement similar to this is often used in hotwire
instruments.
