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MAGNETOSTRICTIVE POSITION SENSORS

The magnetostrictive position sensor made by Temposonics Inc., Cary, NC, induces a pulse in a specially-designed magnetostrictive waveguide by the momentary interaction of two magnetic fields. One field comes from a movable magnet that passes along the outside of the sensor tube; the other field comes from a current pulse or interrogation pulse launched along the waveguide. The interaction between the two magnetic fields produces a strain pulse, which travels at sonic speed along the waveguide until the pulse is detected at the head of the sensor. The position of the magnet is determined with high precision by measuring the elapsed time between the launching of the electronic interrogation pulse and the arrival of the strain pulse. As a result, accurate non-contact position sensing is achieved with absolutely no wear to the sensing components.

The number of times that the sensor element is interrogated to produce a position reading is called circulations. By increasing the circulation/interrogation count and averaging the readings, the effective resolution of the position measurement is increased. Temposonics III sensors do not require multiple circulations. Resolution is available up to 2 microns with a single circulation/interrogation.

There are up to four different types of outputs available with the Temposonics line of sensors: true analog, with resolution determined by the type of customer interface; digitally-derived analog output, where digital is translated into an analog output via a D/A converter; digital pulse output, where a digital pulse in either start/stop or PWM format is available; and digital output, where output is either in SSI binary or Gray code format, as in DeviceNet protocol.

--GJ

For more information contact MTS Systems Corporation Sensors Division, 3001 Sheldon Drive, Cary, NC 27513. 800-633-7609. http://www.temposonics.com.

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