Transducers use magnetostrictive technology

Paul Boughton

The new TLM and TMI linear position transducers from Variohm-Eurosensor offer a wide range of output interfaces coupled with high-speed operation, durability and stroke lengths of up to 4500 mm - a combination that makes them excellent for use in harsh environments that traditionally pose problems, such as high temperatures, high humidity and constant vibration.

Unlike conventional position transducers, the TLM and TMI employ a magnetostrictive technology that uses a magnet as a target.

Normally the transducer body is fixed to a machine bed or body and the magnetic target is attached to a moving part - the position of which is to be measured. One great advantage of this system is that the magnet does not need to be aligned very precisely, ±2mm will not reduce the accuracy. This technology also affords the possibility of sealing to IP67.

Magnetostriction is an absolute measuring system so that the transducer always knows where it is, even after power is removed and restored.

Offering stroke lengths of between 100 and 4500 mm, the TLM and TMI are of a robust design and operate over a temperature range of -40 to +85 degrees C. Measurement accuracy is not affected by the surrounding atmosphere or medium and they are well suited to integration into hydraulic cylinders. Resolution is 0.001 mm irrespective of the stroke length.

Particular attention has been paid to the integrity of the output data and this has led to the development of a special Asic that verifies the validity of the measured value and corrects it for linearity errors. The data transfer rate is 16 kHz and the output is available as either start/stop, SSI or Dymos; this latter format also provides an output corresponding to the true operational speed at which the unit is being operated. The latest variation also offers the possibility of direct connection to a Canopen network.

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