Product Description:

The X20DC137A is a digital counter module produced by B & R Automation for the X20 Fieldbus Input Output Modules series. Within a distributed control architecture, this plug-in unit captures high-speed position or event data from incremental encoders and reports the values to the central PLC over the X20 backplane bus. By performing edge counting and time-stamp generation locally, the module off-loads real-time tasks from the CPU so motion axes or material-tracking stations maintain deterministic sequencing.

The X20DC137A is a Digital Counter Module, meaning the onboard logic is optimized for pulse accumulation rather than simple on/off sensing. It provides 1 counter channel, so one incremental feedback line set can be processed without crosstalk. The input circuit accepts pulse trains up to 300 kHz; this frequency ceiling sets the fastest shaft speed or linear scale velocity that can be resolved without aliasing. Connection is made through an ABR incremental encoder interface, allowing simultaneous decoding of A, B, and reference tracks for bidirectional position evaluation. Because the incoming lines use a differential signal format, immunity to electromagnetic noise is improved, and cable runs can be extended on large machines.

For status verification, there is built-in encoder monitoring that checks supply, wiring integrity, and signal symmetry during operation. The arithmetic core supports a 4x evaluation factor, translating each quadrature cycle into four distinct count steps to increase position resolution. Input circuitry is designed for a 24 V signal level, matching standard sensor supply rails and simplifying power distribution inside control cabinets. Time-critical logging is supported by the NetTime function, which tags each captured edge with a synchronized network time stamp so motion profiles from multiple modules can be correlated precisely across the plant network.