Which method is used to measure very low resistances, typically less than 1/10 of an ohm?

The Kelvin double bridge is specifically designed for the precise measurement of very low resistances, typically less than 1/10 of an ohm. This method utilizes a four-terminal configuration, which effectively eliminates the influence of lead and contact resistances that can significantly affect measurements of low resistances.

In a standard two-terminal measurement (like those conducted with a regular ohmmeter or a simple milliohm meter), any resistance in the leads can introduce significant errors because the leads themselves may contribute a comparable resistance to what is being measured. The Kelvin double bridge mitigates this issue by having separate pairs of terminals for supplying current and measuring voltage, ensuring that only the resistance of the device under test is factored into the measurement.

Using this method provides higher accuracy and reliability in low resistance measurements, making it the preferred choice for applications that require precision in very low resistance scenarios.