How to choose 50mV / 75mV / 100mV shunt resistors
Selecting the shunt voltage drop (mV) is a trade-off between power dissipation, measurement resolution, noise margin and system wiring. This guide helps engineers select a shunt for DC current measurement.
The core trade-off
For a fixed current, increasing the shunt drop (mV) increases the shunt resistance (R = V/I) and therefore increases power dissipation (P = I²·R). Higher mV makes the measurement easier for the ADC (better signal), but increases heating.
Quick rule of thumb
- 50mV–75mV: common industrial choice, good balance of heat vs signal.
- 100mV–150mV: better signal, higher dissipation, often needs better cooling.
- 300mV–500mV: special cases (low current / high noise immunity) — evaluate carefully.
Example: 3000A shunt
Compare dissipation at different mV values:
| Current (A) | Drop (mV) | Resistance (mΩ) | Power (W) |
|---|---|---|---|
| 3000 | 50 | 0.016667 | 150 |
| 3000 | 75 | 0.025000 | 225 |
| 3000 | 100 | 0.033333 | 300 |
| 3000 | 150 | 0.050000 | 450 |
These values assume nominal current continuously. Duty cycle, airflow and mounting affect temperature rise.
Engineering selection checklist
- Signal chain: ADC input range, amplifier gain, noise environment.
- Thermals: continuous current vs duty cycle, ambient temperature, airflow.
- Accuracy: tolerance, TCR, long-term drift, Kelvin sensing requirement.
- Mechanical: busbar integration, footprint, hole pattern, clearances.
- Overload: peak current duration and repetition (very important).
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