Position measurement apparatus and method of using same with sonic pulse

Abstract

A magnetostrictive wire waveguide type position measuring system wherein the wire waveguide is mounted within a small diameter brass tube which, in turn, is mounted by way of resilient suspension components within a rigid outer tube affixed to a position reference frame. The suspension system prevents relatively high frequency shock inputs characteristic of rough environment applications from reaching the waveguide. The position signal is derived from output signal quantities generated by the propagation times of sonic disturbances from a first reference magnet held in a fixed position relative to the outer housing and a second user magnet which moves relative to the outer housing with the element or quantity being monitored. To compensate for longitudinal movement of the waveguide within the floating suspension system and to afford a time interval for further signal compensation purposes, a computer calculates a variable time delay related to the difference between a constant and the propagation time of the reference magnet impulse and adds this variable delay to the user magnet propagation time. Position is determined as a function of the time interval between and original excitation signal and the propagation variably delayed user magnet impulse.