ABB AX521 Analog Input Module 1SAP250100R0001

The ABB AX521, with order code 1SAP250100R0001, is an analog input module designed for the AC500 series programmable logic controllers (PLC). This module provides four differential input channels for measuring standard industrial signals. It is a key component for process control and machine monitoring applications requiring accurate analog measurement.

Input Specifications

Each of the four channels can be individually configured for current input (0-20 mA or 4-20 mA) or voltage input (0-10 V, ±10 V). Resolution is 12 bits plus sign, providing a step size of 5 µA for current and 5 mV for voltage. The module features a common-mode voltage range of ±30 V and input impedance of 250 Ω (current) or >1 MΩ (voltage).

Conversion and Accuracy

Conversion time per channel is 10 ms, with simultaneous sampling on all channels. Accuracy is ±0.3% of full scale at 25°C, with a temperature drift of 50 ppm/°C. The module includes a built-in digital filter to suppress 50/60 Hz noise, selectable via software. Overvoltage protection up to ±30 V prevents damage from wiring errors.

Diagnostics and Status

LED indicators for each channel show wire break (for 4-20 mA loops) and out-of-range conditions. The module also provides a common diagnostic LED for module health. Under-range and over-range detection is programmable, allowing early warning of sensor faults.

Integration with AC500

The AX521 connects directly to the AC500 backplane via a 24-pin connector. It is configured using ABB's Automation Builder or Control Builder Plus software. The module supports cyclic I/O updating, with data available in the PLC's process image. Up to 16 analog modules can be installed per system.

Electrical and Environmental

Power is supplied from the backplane: 5V DC at 55 mA and 24V DC at 30 mA (for field power). The operating temperature range is 0°C to 55°C, with storage from -40°C to 70°C. Humidity tolerance is 5% to 95% non-condensing. The module is rated IP20 and requires a protective enclosure.

Wiring and Isolation

A removable screw terminal block is included for field wiring. Each channel is galvanically isolated from the backplane (500V AC) but channels share a common reference. Shielded twisted-pair cables are recommended for optimal noise immunity. The module dimensions are 72 x 90 x 67 mm (W x H x D).

Applications

Typical applications include monitoring pressure transmitters, temperature transducers (4-20 mA), level sensors, and flow meters. It is widely used in water treatment, HVAC, conveyors, and chemical processing. The four-channel density balances cost and channel count.

Conclusion

The ABB AX521 analog input module delivers reliable, configurable measurement for AC500 PLCs. With four channels, selectable current/voltage ranges, and diagnostic features, it is a practical solution for industrial analog sensing.