Kelvin–Varley divider.

About Kelvin–Varley divider

The Kelvin-Varley voltage divider, named after its inventors William Thomson, 1st Baron Kelvin and Cromwell Fleetwood Varley, is a precision voltage divider circuit used to generate an output voltage as a highly accurate ratio of an input voltage, with selectable resolution over several decades. The concept of multi-decade resistor networks for precise voltage and resistance ratio adjustment was developed in the late 19th century as part of the evolution of electrical resistance measurement techniques. Unlike a simple resistive divider, it employs cascaded stages of matched resistor networks to achieve very high linearity and ratio accuracy, and is typically operated in conjunction with a sensitive null detector. In this role, the Kelvin–Varley divider functions as an electromechanical precision digital-to-analog converter for voltage ratio values.