Passive Rotary Optical Encoder Shrugs Off Harsh Environments

No integral electronics can be found within the encoder housing of a novel rotary incremental optical encoder. Micronor's entirely passive MR312 ZapFree encoder has an all-optical design. Thanks to wave-division-multiplexing (WDM) technology, just a single 62.5/125-µm multimode optical fiber connection is required. With WDM, each optical signal path is assigned a specific wavelength over the same single fiber.

The encoder offers immunity to lightning and atmospheric static that would "zap" conventional encoders. It also outdistances copper cabling by allowing link lengths up to 1000 m (3280 ft). Its inert nature suits it for hazardous and explosive environments, and its intrinsic EMI/RFI resistance enables safe and reliable operation in medical equipment and noisy industrial sites.

Two versions are available, one with 100 parts per revolution and the other with 256. The standard operating-temperature range is ­40°C to 80°C. An extended temperature-range option covers ­60°C to 150°C. The housing is a standard-size 58 package (58-mm outside diameter).

For a turnkey solution, the MR310 remote optical interface is available for standard interfaces. The MR310's outputs are a standard A/B open-collector and a single line-driver quadrature signal.

The MR312 encoder is priced at $635 and the MR310 interface costs $1600, both in 100-unit quantities. For a complete system, users would have to add a 100-ft long commercial-grade optical fiber cable that runs about $100 for installation.