In this topic, you study the Difference Between Moving Iron & Moving Coil Instruments.
|
Point of Comparison |
Moving Coil Instruments |
Moving Iron Instruments |
| Cost | More | Less |
| Power consumption | Less | Slightly more |
| Scale of meter | Uniform | Not uniform |
| Torque to weight ratio | High | Less than M.C. |
| Damping | Eddy current damping used without any damping mechanism. | Damping chamber and mechanism is required. |
| Hysteresis loss | Free | Are present |
| Error due to stray magnetic field | Negligible | Present |
| Use | Used on D.C. only. | Used on both A.C. and D.C. |
| Robustness | Not so robust | Are robust |
| Effect of lifetime | With time strength of permanent magnet reduces causing error in readings | Negligible |
| Effect of frequency | Not used on A.C. | Suitable for low frequency and high power. Readings are correct only for which it is designed. |
| Moving parts | Moving parts are delicate and cost more. | Moving parts are simple and cost less. |
| Operating torque | High | High |
| Deflection | Proportional to I | Proportional to I2 |
| Temperature effect | Negligible | (i) Increases resistance of coil. (ii) Decreases permeability (iii) Decreases stiffness of spring, causing error in reading. |