Which meter has the highest accuracy?

PMMC instruments:

• The scale is uniform (Linear scale)
• High torque to weight ratio compared to all the other type of instruments
• Frequency error or reactance error is absent
• High sensitivity
• Hysteresis loss is lesser
• No internal heating problem
• High accuracy
• Very less power consumption

Important Points

Moving Iron (MI) type instruments:

• Moving Iron (MI) type instruments can be used for both AC & DC measurements. But Moving Iron connected through the current Transformer block DC supply. So that Moving Iron connected through the current Transformer is only used for AC measurements.
• The moving iron meter has a large magnetic reluctance as compared to the PMMC meter. That’s why more power is required to operate the moving iron meter.

Additional InformationComparison of Moving Coil, Dynamometer type and Moving 
Iron Voltmeters and Ammeters: