Wanderlust World Wanderlust World Both moving‑coil and moving‑iron (iron‑vane) meters measure electrical quantities, but their principles, accuracy, and best‑use cases differ significantly.
| Feature | Moving‑Coil (D’Arsonval) | Moving‑Iron |
|---|---|---|
| Operating Principle | Current‑carrying coil rotates in a permanent magnetic field (electromagnetic torque). | Fixed coil magnetizes a soft‑iron vane; repulsion/attraction moves the vane. |
| Construction | Lightweight coil on jeweled bearings, hairspring return, permanent magnet. | Stationary coil, pivoted iron vane/disk, spring return, metal housing. |
| Accuracy | High (typically 1–2 % of full scale), low power consumption. | Lower (2–5 %), affected by hysteresis & temperature. |
| Damping | Eddy‑current (aluminum former) or air damping. | Eddy‑current damping in the iron vane. |
| Frequency Range | DC only (unless rectifier added). | DC & AC (true RMS with proper scaling). |
| Typical Applications | Precision instruments, lab multimeters, galvanometers. | Panel meters, battery testers, low‑cost AC/DC indicators. |
| Cost | Higher. | Lower. |
Bottom line: Choose moving‑coil for precision DC work; moving‑iron for rugged, inexpensive AC/DC panel readings.