POSITAL’s OPTOCODE (OCD) absolute rotary
encoders are now available with a new combined interface that enables
simultaneous communication of both absolute and incremental rotary position
data. The new interface is designed to provide robust and cost-effective
point-to-point communications between encoders and many popular types of
programmable logic controllers (PLC).
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.