Slip rings do an excellent job of transmitting electrical power. However, when used for data communications, some issues could arise due to excessive signal jitter.
Slip rings excel at transmitting electrical power, yet challenges may arise when used for data communications, particularly due to excessive signal jitter. Issues such as excessive vibration of the sliding contacts or a break in signal impedance beyond what the data signal can tolerate may lead to poor performance. While slip rings can perform exceptionally well when new, they may experience performance degradation over time as they wear.
When connecting the RS-485 bus through a slip ring, we recommend setting the pre-initialization of the data buffer to Slow fill (Controller Settings → Settings → Buffer pre-init type). With the slow fill setting, in case of an error during data transfer through the slip ring, the last valid measurement value will be written to the data buffer on the controller. This provides the advantage of ignoring short glitches in bus communication. If the error persists for more than 2 seconds, the buffer is filled with the predefined fill pattern*
The buffer pre-initialization defines which values are written to the data buffer in case of an RS-485 communication error. The available buffer pre-initialization options are:
- Fast fill: In case of an error, the buffer is filled with the predefined fill pattern (default setting).
- Slow fill: In case of an error, the last valid value will be written to the buffer. If the error lasts more than 2 seconds, the buffer is filled with the predefined fill pattern*.
- Deactivated: The buffer is filled with the last valid value.
* The fill pattern defines the default value that is written to the data buffer in case of an error. Valid values range from 0 to 255. This integer number represents a specific bit pattern (e.g., 255 = 1111 1111).