Advantages and disadvantages of PMMC (permanent magnet moving coil)

There are some advantages of PMMC (permanent magnet moving coil) are given below,

  • The PMMC has uniformly divided scale. The scale may be very long, over about 250 degree.
  • It has a very high torque to weight ratio.
  • The PMMC has consumes low power.
  • The PMMC has a very high accuracy.
  • The PMMC is free from hysteresis error.
  • The PMMC has efficient damping characteristics and is not affected by stray magnetic field.
  • Extension of instrument range is possible with the help of shunt and series resistances.

There are some disadvantages of PMMC (permanent magnet moving coil) are given below,

  • It has comparatively high cost.
  • The PMMC has only suitable for d.c. measurements.
  • Aging of permanent magnets and control springs introduces errors.
PMMC

PMMC

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