A 25-bit reference resistive voltage divider

An automated 25-bit reference resistive voltage divider is described. It features microcomputer-controlled self-calibration and autobalancing voltage ratio measurement to eight significant digits, with an uncertainity (2σ) of three parts in 10⁸ (of the 10-V input) or the equivalent of one least significant bit (LSB). To achieve this accuracy, sources of error have been critically examined, carefully controlled, and accounted for.