Allen-Bradley 1771-QB Linear Positioning Module

The Allen-Bradley 1771-QB Linear Positioning Module is a dual-axis, PLC-5‑compatible closed‑loop motion controller that occupies a single slot in the 1771 Universal I/O backplane. It is designed for hydraulic servo control using magnetostrictive linear displacement transducers, providing two independent feedback channels that drive servo valves via analog outputs. The module updates each axis every 2 ms, with a backplane current load of about 1.1 A typical (up to 1.6 A max). It accepts auxiliary digital inputs of 8 mA per input at 12 V DC or 16 mA per input at 24 V DC, with logic thresholds of 0–4 V for logic 0 and 10–30 V DC for logic 1. For actuation, it delivers servo valve signals as analog outputs at 10 V DC reference with drive currents of 20 mA, 50 mA, or 100 mA. The 1771-QB integrates machine control for precise linear positioning in automation, making it suitable for applications that require coordinated motion control of hydraulic actuators via magnetostrictive sensors within a single module, simplifying rack layouts while delivering reliable closed‑loop performance for positioning tasks.