The new interface reports absolute rotary position data to the PLC using the synchronous serial interface (SSI) standard, operating over an RS-422/485 communication link. At the same time, the encoder can also transmit a series of electronic pulses as the shaft rotates – up to 16,384 pulses per rotation. Optionally, an index pulse can also be sent once every complete rotation. Incremental pulses can be sent over an RS-422/485 link, or via a push/pull connection. (The incremental pulses are sent over separate wire pairs from those used to enable the SSI interface.) These “dual-personality” encoders can be extremely useful for motor control applications or for monitoring rotating machinery such as wind turbines, since they can provide accurate real-time measurement of the rotational velocity (thanks to the incremental output), while also providing access to absolute rotary position data in response to a request from the controller.
Other new features of these encoders include enhanced diagnostic reporting via case-mounted LED’s or via the SSI connection, and an optional case-mounted push-button that allows the operator to re-set the zero-position (datum) of the absolute position readout. The new OCD encoders retain the best features of the previous generation devices, including precision (up to 216 steps per turn) accuracy, single- or multi-turn capabilities and highly effective shaft and connection seals (up to IP66 protection). Available as solid, hollow and hub shaft versions, the units can be supplied with a connector or a cable exit.