Difference Between Moving Iron and Moving Coil Meter

The difference between Moving iron meter and Moving coil meter is, moving iron meter operates on electromagnetic principle. Whereas, moving coil meter works on DC motor principle.

Moving Iron meter measures DC current, AC current, DC voltage, AC voltage. When current flows in the coil winding, the moving iron produces a magnetic field by repulsion. They are divided into two moving iron meters as repulsion type and attraction type. As this meter is non-directional it can be used in AC and DC circuits.

Coming to Moving coil meters, these are popular than moving iron type. They are high in accuracy and sensitivity. They can only measure DC signals.

When current flows through the moving coil, it produces a magnetic field. This induced field generates torque and moves the coil and deflects the measuring scale. Here is the comparison between Moving iron meter and moving coil meter.

Difference between Moving Coil and Moving Iron Meter

Moving Iron MeterMoving Coil Meter
It works on the principle of electromagnetic effectIt works on the principle of DC motor
Cheap and simpleCostly and weight increases due to the magnet
Non-uniform scaleUniform scale
Gravity control method is usedSpring control method is used
Deflection torque is proportional to the square of currentDeflection torque is proportional to the current
Moving Iron meter use Air dampingMoving Coil uses Eddy current damping
Reliable accuracyAccuracy is high
High power consumptionLow power consumption
Moving Iron can be used in AC and DC circuitsMoving Coil can be used in DC circuits only
Used as ammeter, voltmeter, wattmeterUsed as ammeter, voltmeter, ohmmeter, galvanometer

Summary

Other than the above differences, the moving coil instrument has a frequency limits ranging from 20 to 200 Hertz. Here are some advantages and disadvantages of moving iron.

Moving Iron voltmeter (Moving coil instrument) indicates a non-linear scale and the Moving coil indicates a linear scale. When comparing both, moving coil meters have good sensitivity and low power consumption. They are also well protected from stray magnetic fields.

The disadvantage with moving coil meter is it is suitable for DC and is more expensive than moving iron type. The advantage of moving iron type is a robust construction, cheap and detects RMS voltages and currents accurately.

Leave a Comment