Question

disadvantages of permanent magnet moving coil type of instruments

Answer 1

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

Answer 2

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