Which of the following is a disadvantage of PMMC instruments?

Which of the following is a disadvantage of PMMC instruments?

Right Answer is:

All of the above

SOLUTION

PMMC (Permanent Magnet Moving Coil) instruments, while offering several advantages, also have some limitations:

  • Cost: PMMC instruments are generally more expensive to manufacture compared to moving iron instruments due to the use of permanent magnets and precision components.

  • DC Measurements Only: PMMC instruments can only be used for measuring DC (Direct Current). They cannot be directly used for measuring AC (Alternating Current) because the direction of the current reverses periodically, causing the pointer to oscillate rapidly.

  • Error Due to Loss of Magnetism: The permanent magnet used in PMMC instruments can lose its magnetism over time due to aging, demagnetization, or exposure to strong magnetic fields. This loss of magnetism can lead to measurement errors.

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