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Position sensor detects up to 30 points on one axis

27 September, 2008

The sensor specialist MTS has announced a non-contact position sensing technology that can measure up to 30 positions along an axis using a single sensor. The Temposonics magnetostrictive technology is said to offer considerable savings over conventional displacement sensors or rotary encoders.

Temposonic sensors

In a typical application, such as a machine with different cutting widths, a position magnet is assigned to each cutting tool. The profile- or rod-shaped sensor, which can be up to 20m long (above), is mounted parallel to the motion axis and travels independently. Each magnet generates an individual signal that travels along the sensor simultaneously.

Inside the sensor, a torsional strain pulse is induced in a magnetostrictive waveguide by the momentary interaction of two magnetic fields. One field comes from one of the magnets passing along the outside of the transducer tube, while the other is generated from a current pulse applied to the waveguide. The interaction between the two fields produces a strain pulse which travels along the waveguide until it is detected at the head of the transducer. By measuring the time between the current pulse being applied, and the arrival of the strain pulse, the position of the moving magnet can be determined.

The linearity of the measurements is said to be better than ±0.01% of full scale, and the repeatability better than ±0.001% FS.

The number of positions that can be sensed, depends on the fieldbus system being used. Versions based on CANbus and Profibus can measure up to 30 positions simultaneously, while a version with an EtherCAT output can measure up to 20 positions in one cycle in the asynchronous mode, or five positions and velocities in the synchronous mode.

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