German Firm's Inductive Displacement Sensors Reach New Low (in Size)

Engineers and developers looking for linear variable differential transformers (LVDTs) for confined spaces and harsh environments now have an option from Hoffmann + Krippner Inc. Late last year, the Germany-headquartered company debuted its Inelta IZAL series of slim inductive displacement sensors. Thanks to differential sensing, the new sensors, whose housing diameter is 4 mm, reportedly ensure precise path length measurements in highly confined spaces.

The Inelta IZAL series resulted from a partnership with two other German companies: INELTA Sensorsysteme GmbH & Co KG and PIL Sensoren GmbH. The contactless sensors for displacement and position detection achieve a linearity tolerance of ± 0.5% (optionally 0.25%) and are designed for measuring ranges of 1 mm, 2.5 mm, and 5 mm.

(Source: Hoffmann + Krippner)

With a housing made of chemically nickel-plated steel (IP65 rated) and a temperature range of -25C to 85C (which can be extended even further in custom versions), the sensors are suitable for use in harsh conditions. They are reported to have a measurement sensitivity of up to 130mV/V/mm), a carrier frequency (supply frequency) of 40 kHz, and a temperature coefficient of <± 0.05% FS/°C.

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Jens Kautzor, CEO of Hoffman + Krippner, told Design News that the series brings something new to the market. “Designs with similar specifications like IZAL have diameters starting at 9.5 mm, or do not reach the required low linearity. Most models that are comparable have 2% to 5% linearity,” said Kautzor, who noted that customers have been asking for sensors with a maximum linearity of 0.5%.

“These can be used wherever space is limited and high repeatability is required,” he said. “Here, we have endless possible applications, chief among them pipe sewer cleaning systems, drill spindles, medical technology, testing facilities, and more.”

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The company says it’s willing to provide custom sensor versions with additional equipment options such as individual calibrations. The series’ actuation takes place via an unguided core, with the sensors being connected via a 1-mm cable (optionally available in other lengths). According to Kautzor, the small coils are wound using a special winding machine, and the number of windings and winding layers, as well as the insulation between layers, play a key role in making the IZAL series possible.

“The special feature is the winding technology, combined with the highest level of craftsmanship,” he said. “There are lacquered copper wires, thinner than a hair, wrapped extremely uniform under the microscope by hand. This guarantees the low linearity error at this small size. The windings are the decisive parameter for the quality and functionality of the sensor.”

Tracey Schelmetic graduated from Fairfield University in Fairfield, Conn. and began her long career as a technology and science writer and editor at Appleton & Lange, the now-defunct medical publishing arm of Simon & Schuster. Later, as the editorial director of telecom trade journal Customer Interaction Solutions (today Customer magazine) she became a well-recognized voice in the contact center industry. Today, she is a freelance writer specializing in manufacturing and technology, telecommunications, and enterprise software.