The principle of magnetostriction is illustrated in Figure M.5. In the position sensor, a pulse is induced in a magnetostrictive waveguide by the momentary interaction of two magnetic fields: one from a magnet passing along the outside of the sensor tube; the other field from a current pulse launched along a waveguide within the tube. The interaction produces a strain pulse (twisting the waveguide) that travels at sonic speeds down the waveguide until detected at the sensor head. Measuring the elapsed time between the launching of the electronic pulse and the arrival of the strain pulse, or pulses, precisely determines the position of one, or more, magnets.
Such noncontact position sensing produces no wear in the sensing elements, cutting maintenance and extending sensor life. The encapsulated waveguide and electronics also provide durability in severe environments. And modularity gives mounting flexibility and easy integration.
FIGURE M.5 Principle of magnetostriction.
