A proving ring is a device used to measure force. It consists of an elastic ring in which the deflection of the ring when loaded along a diameter is measured by means of a micrometer screw and a vibrating reed. The proving ring was developed by H.L. Whittemore and S.N. Petrenko of the National Bureau of Standards (NBS), the precursor of the National Institute of Standards and Technology (NIST), in 1927.