Rugged Hybrid Resolver Replaces Optical Encoders

A rugged, self-contained, resolver-based encoder, the Shaft-Tracker from Computer Conversions Corp. can replace less reliable optical shaft encoders. The device provides both incremental and true absolute position outputs with a resolution of 4096 counts/turn. Packaged in a robust NEMA 12/4-rated housing, the Shaft-Tracker's 4-in. length and standard 2.5-in. square mounting flange allow quick and easy direct replacement of standard optical encoders. Since the shaft transducer used is a very reliable resolver, the encoder is free of problems caused by limited-life brushes, light sources, fragile optics, brush noise, ambiguities, and limited resolution often associated with conventional optical or mechanical encoders.

The absolute position data is transmitted in a very simple serial format. It includes three user-operating modes for a high-speed synchronous serial interface or a very basic shift-register-style output that requires only one discreet input and output bit to interrogate the data. Both the absolute and the incremental outputs feature differential line drivers for long data transmissions in electrically noisy environments. The isolated outputs may be used to multiplex up to 32 shaft encoders into a single encoder counter or motion control, resulting in very low-cost multi-axis systems. The absolute data uses RS-485 line drivers that allow multi-drop operation and permit the use of twisted-pair wires for transmission up to 3000 ft. Power inputs are field-adjustable for +5 V dc or 11 to 30 V dc for long cables or more electrically noisy applications.