Accurate measurement of low resistances (under 100Ω) requires four-wire Kelvin sensing rather than a standard two-probe multimeter approach. Using a current-limited power supply and two DMMs — one measuring current, one measuring voltage — eliminates lead resistance errors. Key pitfalls include thermoelectric voltages at dissimilar-metal junctions (mitigated by reversing supply polarity and averaging), DMM accuracy limits at low current ranges, and PCB layout errors. The article explains how CAD tools treat sense resistor pads as two-terminal components, creating subtle routing mistakes when Kelvin sense connections are needed. A nodal four-terminal schematic approach is recommended, though most layout tools lack native support for virtual Kelvin pads, requiring workarounds. Material conductivity measurement via four-point probes is also covered.
