Difference between moving coil and moving iron instrument

Both these instruments are commonly used for indicating and measuring purposes. The difference between moving coil and moving iron instrument is discussed in this article.

Moving iron instrument

Its name speaks for itself. Moving iron instrument means the moving part is an iron piece (soft iron piece basically).

It works on the principle that the electromagnet produces a magnetic field, which attracts or repels the soft iron piece.

MI instrument is classified into two types one is attraction type and another is repulsion type.

Attraction type MI instrument works on the principle of attraction of the iron piece

Repulsion type MI instrument works on the principle of repulsion between the two iron pieces

Moving coil instrument

As its name suggests in this instrument a coil moves and produces deflection.

The moving coil instruments work on the principle that, when a current-carrying is placed in the field of the permanent magnet. A torque is exerted on the coil.

PMMC is an example of a moving coil instrument.

Difference between moving coil and moving iron instrument

Moving ironMoving coil
It works on the principle of magnetismThe working principle of this instrument is similar to the DC motor
The soft iron piece is used as rotating elementsThe coil is used as a rotating element
Basic range: 10mA-100ABasic range: 10µ -100mA
It can be used with both AC and DCIt can be used only with DC
Deflection is proportional to the square of the currentDeflection is proportional to current
Controlling torque is produced by gravitySpring produces the controlling torque
It uses air dampingIt uses eddy current damping
It has a non-uniform scaleIt has a uniform scale
This instrument consumes high powerThe power consumption of these instruments is low
It is less accurate but if designed properly it can be very accurateThe accuracy of this instrument is very good for dc measurement
It is not the very sensitive instrumentIt is a very sensitive instrument
It is not an expensive instrumentIt is an expensive instrument
Moving iron instrument used as an indicating instrumentMoving coil instrument used as a measurement instrument

Key difference between moving coil and moving iron instrument.

The difference between moving coil and moving iron instrument is written in sections.

Quick summary

  • The basic difference between moving coil and moving iron instrument is MI instrument works on magnetism principle and moving coil instrument works on the principle similar to DC motor.
  • MI instrument used as indicating instrument and the moving coil instrument used for measuring purpose.

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