Signal Conditioners, Isolators, and Intrinsic Safety Barriers

Signal interface modules provide the electrical link between field instruments and the control system. In this category, the main Allen-Bradley families are Bulletin 931 signal conditioners and Bulletin 937 intrinsic safety barriers. These products are used to isolate, convert, split, linearize, or amplify signals, while supporting safer interfacing in standard and hazardous area applications.

Bulletin 931N Nano and 931S Smart modules are commonly used when a field signal needs conditioning before it reaches a PLC, DCS, or other automation platform. They are also applied when galvanic isolation is needed or when ground loop and electrical noise problems must be reduced.

Supported signal types include analog, bipolar, thermocouple, RTD, linear resistance, and potentiometer.

Allen-Bradley Product Families

• 931N Nano signal conditioners are suited to applications that need compact DIN-rail mounting and straightforward signal conversion in limited panel space.

• 931S Smart signal conditioners are a strong fit when broader configuration capability is needed for more complex analog and temperature signal handling.

• 937T isolator barriers provide galvanic isolation for intrinsically safe circuits that are electrically separated from the control system.

• 937C converter barriers are used with hazardous area instruments such as temperature sensors or load cells when the signal must be converted to standard outputs such as 0/4…20 mA or 0/2…10 V.

• 937Z Zener barriers are selected where intrinsic safety protection and a narrow profile are required.

How to Choose the Right Interface Module

Choose signal conditioners when the main need is isolation, conversion, splitting, linearization, or amplification inside a general industrial control panel. Choose intrinsic safety barriers when field devices are installed in hazardous locations and the circuit must limit electrical energy as part of an intrinsic safety design.

For tight panel layouts and fixed signal tasks, compact conditioners are often the better choice. For applications that need adjustable ranges or more flexible analog and temperature handling, smart conditioners are typically the better fit.

In hazardous area systems, isolator barriers are often preferred when galvanic isolation and simpler grounding arrangements are important. Zener barriers are commonly used for simple, space-saving intrinsic safety protection. Converter barriers are used when a hazardous area device signal must be translated into a standard control signal for the rest of the system.

Typical Industrial Automation Applications

These signal interface modules are used in process skids, production equipment, manufacturing systems, and industrial control panels that connect transmitters, temperature sensors, load cells, and other analog instruments to PLC-based platforms. Bulletin 937 barriers are also used in hazardous locations, including chemical, petrochemical, and oil and gas applications.

Selection usually depends on signal type, the need for galvanic isolation, hazardous area classification, channel density, power wiring approach, and maintenance preferences.

Relevant features across these families include DIN rail power distribution for Bulletin 931 products, dual-channel and loop-powered options, onboard error indication, DIP-switch configuration, and line fault detection on Bulletin 937T modules.