Thomson bridge
The Thomson bridge is a bridge circuit. It corresponds in its approach to the Wheatstone bridge with the difference that with the Thomson bridge small and smallest resistances can be measured, up to conductor resistances.
These are measurable resistance values from the micro-ohm range (`10^-7`) to the single- digit ohm range. Since the measurement of extremely low resistance values( Rx) can be distorted by conductor resist ances and lead resistances, these are eliminated by the bridge arrangement of the Thomson bridge. For this purpose, a voltage divider consisting of R1 and R2 is connected in parallel with the lead resistance (R) to compensate for the lead resistance. This technique, which works with Kelvin terminals, is also called four- wire measurement.
The Thomson bridge is named after the English physicist William Thomson, Lord Kelvin, who established the absolute temperature under the name Kelvin.