B&R X20AT2222 Analog Input Module (Pt100 / Pt1000 RTD)

The B&R X20AT2222 is a dedicated analog input module for resistance temperature detectors (RTDs), specifically Pt100 and Pt1000 sensors. It provides two independent channels, each configurable for 2‑wire or 3‑wire connections. The module uses a 16‑bit delta‑sigma ADC with selectable filter times, delivering high resolution and noise rejection. The X20AT2222 is part of the X20 system, a modular I/O platform for B&R PLCs. It features channel‑to‑bus isolation of 500 Vrms, making it suitable for industrial environments where ground loops and electromagnetic interference are concerns. The module automatically linearizes the sensor signal according to EN 60751.

Technical Specifications

Functional Description

The X20AT2222 uses a constant‑current excitation method to measure the RTD resistance. For 3‑wire connections, the module compensates for lead wire resistance, eliminating measurement errors due to cable length. The conversion method is sigma‑delta with a built‑in 50/60 Hz noise filter. The output data format is INT (signed integer) or UINT, with a scaling of 0.1°C per bit (e.g., 2500 = 250.0°C). The module provides diagnostics for open circuit, short circuit, and range over/under. Status LEDs per channel indicate sensor connection health.

Configuration and Programming

The X20AT2222 is configured within B&R Automation Studio. Parameters include sensor type (Pt100 or Pt1000), connection method (2‑wire or 3‑wire), filter time, and conversion format. The module is automatically detected by the X20 CPU and assigned a variable name. The user can read the temperature value directly in engineering units (0.1°C) after scaling. The module supports runtime monitoring of sensor errors via status words.

Diagnostic Features

Status indicators:

• Green RUN LED: Module operational

• Red ERROR LED: Module fault

• Yellow LED per channel: Sensor open circuit or out‑of‑range

The module reports detailed diagnostic information to the PLC, including wire break, measurement range violation, and internal reference fault. Error codes are stored in the system diagnostic buffer.

Applications

The X20AT2222 is used in industrial heating and cooling systems, drying ovens, HVAC monitoring, plastic processing machinery, and food processing equipment. It is also suitable for laboratory incubators and environmental test chambers.

Installation Overview

The module mounts on a DIN rail (35 mm) in an X20 backplane. It uses 6‑pin or 12‑pin terminal blocks (field wiring). For 3‑wire RTDs, connect the three wires to terminals (e.g., U1, I1, V1). Use shielded twisted‑pair cable for longer distances (>30 m). The shield should be grounded at the module end only. The module is hot‑swappable in the X20 system.

Conclusion

The B&R X20AT2222 offers high‑accuracy, isolated RTD input for industrial temperature measurement, with flexible configuration and robust diagnostics for X20‑based automation systems.