Which one of the following statement is NOT true about PMMC type instruments?

• A. The cost of PMMC instruments is high
• B. Stray magnetic errors are small in these types of instruments
• C. PMMC type Instruments have uniformly divided scale
• D. These instruments are suitable for both AC and DC currents

Answer: (D)

The principle on which a Permanent Magnet Moving Coil (PMMC) instrument operates is that a torque is exerted on a current-carrying coil placed in the field of a permanent magnet.
PMMC type of instrument can be operated in direct current only. In alternating current, the instrument does not operate because in the positive half the pointer experiences a force in one direction and in the negative half, the pointer experiences the force in the opposite direction. Due to the inertia of the pointer, it remains in its zero position.