shuntresistor

A shunt resistor, or current sense resistor, is a low-value precision resistor used to measure electrical current by producing a small, accurately proportional voltage drop across its terminals. Because it must carry large currents with minimal voltage loss, the resistance is typically in the milliohm range (or lower), yielding voltages on the order of millivolts for moderate currents. The voltage is usually amplified by a differential amplifier, often with Kelvin (four-wire) connections to minimize errors from lead resistance and contact resistance.

Shunt resistors are designed for high stability and power handling. They are commonly made from stable alloys such as manganin or constantan, or from low-temperature-coefficient copper alloys and metal foils. Packages range from through-hole or surface-mount chips to flat, bar-like elements with integrated busbars or heatsinking. Tolerances commonly range from 0.1% to 1%, and many devices specify low temperature coefficients to limit drift with temperature.

Performance considerations include the relationship V = I × R, and the power dissipation P = I^2R. Self-heating raises resistance and introduces drift; adequate cooling and margin on the rated current are needed. Parasitic inductance and capacitance, contact resistance, and nonlinearity at high currents can affect accuracy, particularly in fast or pulsed measurements; Kelvin connections and careful layout help mitigate these effects.

Applications include current measurement in power supplies, battery management systems, motor drives, inverters, automotive electronics, and test equipment. Shunt resistors are chosen based on the required sense voltage, current range, tolerance, temperature stability, and physical constraints such as board space and thermal management.