Kelvin connection (4-wire sensing) for shunt resistors

Kelvin sensing (4-wire measurement) separates current path and voltage sensing to reduce errors caused by contact resistance, busbar drops and thermal gradients.

Why 2-wire measurement is inaccurate

In 2-wire measurement, the measured voltage includes drops on terminals, joints and current-carrying conductors. For very low resistances (micro-ohms to milli-ohms), those drops can be significant and unstable.

How Kelvin (4-wire) works

Use two heavy terminals for current (high current path).
Use two separate sense terminals (Kelvin taps) for voltage measurement.
Measure voltage directly at defined sense points to minimize parasitic contributions.

Best practices

Keep sense wires twisted pair and away from high current conductors.
Use proper shielding in high EMI environments.
Sense wiring should be routed to avoid thermal hotspots.
Define the sense points in drawings/specs for repeatable accuracy.

Common mistakes

Connecting sense wires to the power terminals instead of Kelvin taps.
Long sense loops near switching power devices (noise pickup).
Shared ground returns that inject current into the sense path.

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FAQ

Do I always need Kelvin connection for shunts?

For low-resistance shunts and high current, Kelvin sensing is strongly recommended to reduce measurement error from terminals and conductor drops. For very low current and higher resistance, it may be less critical.

Can Kelvin sensing reduce drift?

Kelvin sensing reduces errors from contact resistance and wiring drops. Drift still depends on shunt material, temperature rise and TCR, but Kelvin sensing improves repeatability and accuracy in real installations.