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 Meter | Moving Coil Meter |
|---|---|
| It works on the principle of electromagnetic effect | It works on the principle of DC motor |
| Cheap and simple | Costly and weight increases due to the magnet |
| Non-uniform scale | Uniform scale |
| Gravity control method is used | Spring control method is used |
| Deflection torque is proportional to the square of current | Deflection torque is proportional to the current |
| Moving Iron meter use Air damping | Moving Coil uses Eddy current damping |
| Reliable accuracy | Accuracy is high |
| High power consumption | Low power consumption |
| Moving Iron can be used in AC and DC circuits | Moving Coil can be used in DC circuits only |
| Used as ammeter, voltmeter, wattmeter | Used 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.
