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Inductosyn: End of an Era, New Opportunities or Both?

Recently, obtaining the Inductosyn and components for maintenance has become more difficult. For decades the Inductosyn from Farrand Controls / Ruhle Companies sat near the top of the rotary sensor hierarchy. Providing sub 2 arcsec (0.5 mdeg) accuracies, it combined the robustness of a resolver with the performance of the best optical encoders. Despite its shortcomings, it found plenty of customers, from airborne infrared and radar systems, to telescopes, satellite communication antennae (SATCOM), machine tooling and low-pressure vacuum chambers.  

Typical Inductosyn Transducer to Digital Output Subsystem Figure from ‘Precision Inductosyn Position Transducers’ Brochure, Farrand Controls, NY, USA

Over the past decade, advances in traditional rotary encoders have significantly closed the gap that once existed between encoders and the Inductosyn. For some existing applications with inner diameters less than ~175mm (~7”) the transition to a modern rotary encoder, capable of 2 mdeg of accuracy (or even better) and combined with a modern digital output such as SSI or BiSS, may be the best path forward. For larger mechanical setups and those applications requiring fractional mdeg of accuracy, keeping with an Inductosyn-like technology may be the best option.

Modern encoders have all of the active components on the stator, including A/D processing. Furthermore, the rotor is typically passive and doesn’t require wiring.

At Everight Position we take the time to learn about your application and can provide a path forward to maintain an existing Inductosyn setup as well as the potential migration to a modern rotary encoder. 

As a US corporation and NIST800.171 compliant, Everight Position can help each step of the way. We look forward to working with you.

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