초록 ▼

In a position detection probe having a magnetostrictive wire stretched between a head and a reflective foot end termination, and a magnet displaceable along the probe and using the sonic pulse propagation time from the magnet to the foot as a position detection parameter, compensation for thermal ex

In a position detection probe having a magnetostrictive wire stretched between a head and a reflective foot end termination, and a magnet displaceable along the probe and using the sonic pulse propagation time from the magnet to the foot as a position detection parameter, compensation for thermal expansion and thermal change of propagation velocity is made based on the property of the total propagation time along the wire length being a unique function of temperature and calibrating the probe at different temperatures to yield either equations or look up tables of true positions as functions of the total propagation time and the position detection parameter. By mapping wire characteristics at a plurality of magnet positions and temperatures to construct look up tables, wire nonlinearities as well as thermal effects can be compensated for.

대표청구항 ▼

In a linear magnetostrictive position detector having a magnetostrictive wire stretched between a fixed head and a reflection termination wherein propagation characteristics of the wire including propagation velocity and the wire length, and the position of the termination are dependent on temperatu

In a linear magnetostrictive position detector having a magnetostrictive wire stretched between a fixed head and a reflection termination wherein propagation characteristics of the wire including propagation velocity and the wire length, and the position of the termination are dependent on temperature, a magnet movable along the wire, means for inducing sonic pulses in the wire traversing the direct distance between the head and the magnet over a first propagation time and the indirect distance between the head and the magnet via reflection at the termination over a second propagation time, means for measuring the propagation times of the sonic pulses, and circuit means responsive to the measured propagation times of the pulses for determining the position of the magnet; the method of measuring the magnet position and compensating for the effects of temperature changes on propagation characteristics comprising the steps of: determining the propagation characteristics of the wire as a function of the sum of first and second propagation times, wherein the sum is representative of the wire length and propagation velocity; measuring the sum of the first and second propagation times; measuring the difference of first and second propagation times at a given magnet position; and calculating the given position from the difference of propagation times and from the propagation characteristics represented by the sum of the propagation times.