Tensioned-Wire Length Measuring Instrument

Abstract

Length measurement using tensioned-wires has been investigated showing that sensitivities of 1 part in 10 10 are realistic with stabilities of 1 part in 10 8 for at least 100 hr periods when detecting small changes of a large nominal length. Wires may also be used to measure continuous lengths from millimetres to decametres with about 4 parts per million repeatability. The existing static theory has been extended to cover dynamic performance and the effect of tensioning-head friction and inertia. Temperature, creep and mechanical hysteretic errors are discussed. A number of specific instruments are described for making a wide variety of dimensional measurements.