Magnetostrictive sensing has a lot to offer: the devices don't wear, aren't prone to backlash, and don't need extra electronics for converting ac signals into dc. They've good shock and electrical immunity too, and they work well in harsh environments. Yet, until now, the technology has been too expensive to warrant much consideration for positioning feedback. Now that may be changing as manufacturers figure out ways of driving costs from the devices.
Tol-o-matic engineers removed cost from their new APF actuator by designing the transducer as an integral piece of the motion device, eliminating some parts redundancy. APF--short for absolute position feedback--is available on the company's B3S electric and BC3 pneumatic actuators.
The company embeds the sensor into the rodless actuators up to 120 inches long for electric and 156 inches for pneumatic ones. Pricing competes with other sensing options, the company says, as an adder beginning somewhere below $500.
Tol-o-matic claims ±0.005-inch linearity for its rodless cylinders using magnetostrictive position feedback on strokes out to 20 inches. For longer lengths, the company says linearity is between ±.025 percent of the full stroke. Repeatability is =0.003 inch.
APF actuators eliminate homing routines from an operating sequence both after a cycle stop and following power loss. With this latest positioning feedback, load location is always a known.
Jesse Russell, manager of market development for sensor maker MTS Systems Corp., says that for high-volume, embedded products, the cost of magnetostrictive sensing is sometimes falling below that of LVDTs, especially when there's signal conditioning involved. And, magnetostrictive sensing can be "head-to-head competitive" with potentiometers, he adds.
Contact:Jim Drennen, Tol-O-Matic, Inc.
Jesse Russell, MTS Systems Corp.
MTS Systems Corp.
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