Product Description:

B&R Automation's 8AC120.60-1 belongs to the 8AC Powerlink Modules series and functions as an encoder interface for distributed motion control. Mounted close to a servo drive, the module connects a sine/cosine feedback device through its RS-485 channel and presents position data to the Powerlink network. In an industrial automation cell, this arrangement permits precise synchronized axis control while keeping noisy analog signals inside the cabinet and minimizing the cable lengths that must cross the factory floor.

The module exchanges data at 625 kbaud, which gives the interface a bit time of 1.6 µs. Physical wiring to the encoder is completed through a 15-pin female DSUB connector that carries power, differential signal pairs, and two sense conductors. The logic section is supplied from a 5 V rail and typically draws only 250 mA, so several modules can share the same backplane without overloading the supply. A board-mounted 120 Ω termination matches the line impedance to the twisted-pair cable and suppresses reflections on extended runs. The two sense lines provide up to 0.7 V of compensation each, allowing the module to correct voltage drop and maintain stable encoder excitation. Differential, symmetrical sine and cosine signaling further improves immunity to electrical noise.

The analog front end accepts sine and cosine signals up to 400 kHz (-5 dB), enabling accurate feedback from high-speed motors. Shielded cabling of up to 50 m can be used, and a single encoder input is available for connection. Hardware interpolation raises feedback granularity to 16384 × encoder lines, which supports tight velocity and position loops. A common-mode tolerance of ±7 V guards the receiver against ground shifts that are typical in large machines. The module permanently monitors encoder presence and signal quality, and because encoder-to-drive isolation is not provided, the installation must ensure a shared reference potential to avoid communication errors.