| Full Form | Permanent Magnet Moving Coil | Electrodynamometer Moving Coil Instrument |
| Principle | Force on current-carrying conductor in permanent magnetic field | Interaction between fixed coil field and moving coil field |
| Operating Torque | Td=BINAT_d = BINATd=BINA | Td=I1I2dMdθT_d = I_1 I_2 \frac{dM}{d\theta}Td=I1I2dθdM |
| Deflecting Torque | Proportional to Current (I) | Proportional to Product of Currents (I₁I₂) |
| Scale | Uniform / Linear | Non-uniform (Crowded at lower end) |
| Accuracy | Very High | High |
| Sensitivity | Very High | Moderate |
| Power Consumption | Low | High |
| Damping | Eddy Current Damping | Air Friction Damping |
| Magnetic Field | Permanent Magnet | Electromagnet (Fixed Coil) |
| Torque/Weight Ratio | High | Low |
| Frequency Effect | No effect (DC only) | Affected slightly |
| Hysteresis Error | Negligible | Present |
| Eddy Current Error | Small | Negligible |
| Cost | Lower | Higher |
| Robustness | Delicate | Robust |
| Reading Stability | Excellent | Good |
| Calibration | Easy | More difficult |
| Stray Magnetic Field Effect | Less | More |
| Maintenance | Low | Moderate |
| Efficiency | High | Lower |
| Scale Equation | θ ∝ I | θ ∝ I² |
| Best Used As | DC Ammeter, Voltmeter | AC/DC Ammeter, Voltmeter, Wattmeter |