AB Bulletin 1794 and 1797 LEX I/O and FLEX Ex I/O Systems

AB Bulletin 1794 and 1797 LEX I/O and FLEX Ex I/O Systems

FLEX I/O System

System Overview: Connects to a wide range of networks and features a modular design for high flexibility and low cost for distributed applications. 

Up to eight I/O modules can be connected to a single adapter, supporting a wide range of I/O point combinations.

Designed for extreme environments, the FLEX I/O XT is coated for protection, meets many standards, 

and is resistant to a wide range of reactive substances.

Module Options

Digital I/O modules: Covering a wide range of electrical ranges such as 120V AC, 220V AC, 24V DC, etc., available in different densities from 8 to 32 points. 

Features isolation, protection, diagnostics, optional input filtering time, and LED status indication for each channel.

Analogue, thermocouple and RTD modules: channels can be individually configured, support online configuration, selectable input filters, etc., 

capable of controlling the operation of output devices under abnormal conditions, different modules have different accuracy and resolution.

Counter modules: Selected according to the type of application and field equipment, such as 1794 - IJ2XT for proportional control, 

1794 - VHS for packaging, material handling, etc.

System mounting and accessories: Panel or DIN rail mounting, with grounding, using DIN rails made of zinc-plated yellow chrome steel. 

A wide range of accessories are available, such as extension cables, mounting kits, DIN rail latches, etc., 

and comprehensive documentation is also available.

FLEX Ex I/O System

System overview: Intrinsically safe for use in hazardous areas, eliminating the need for explosion-proof enclosures 

and additional intrinsically safe isolation components. Based on a physical architecture, categorised by hazardous area designation, 

connectable to a wide range of networks, modules can be plugged and unplugged electrically and have a wide range of protection features.

Module Options

Digital I/O modules: Fault detection, indication and reporting, selectable input filter time, LED status indication for each channel.

Analogue module: channel configurable, with on-board calibration, online configuration, etc., can detect over-range and under-range,

and can control the operation of output devices under abnormal conditions.

Counter I/O Module: Suitable for applications such as tacho control, reports frequency, acceleration and direction, and receives and returns binary data.

System Installation and Power Supply Selection: Requires selection of the appropriate adapter and distribution method, with a variety of adapters available. 

Power supplies are available in N-type (vandal-proof) and E-type (fire-proof) housings, 

complying with North American and European standards, respectively, and offering different input voltages. 

The number of power supplies and their distribution need to be determined according to system planning. Documentation is available to support this.

caveat

Safety Related

Follow safety guidelines: Solid-state equipment has different operating characteristics than electromechanical equipment and should be used in accordance with the Safety Guide for the Application, Installation, and Maintenance of Solid-State Control Equipment, publication SGI-1.1, to ensure that the equipment is applied only in an acceptable manner. Rockwell Automation is not responsible for indirect or consequential damages resulting from the use of the equipment.

Hazardous Environment CAUTION: Multiple operations in a hazardous environment can result in an explosion, which could cause injury, death, damage, or financial loss. For example, when installing in a hazardous area, operations such as connecting or disconnecting communication cables, wiring, and inserting or removing modules may cause an explosion due to electric arcs if they are performed under live power. Therefore, always ensure that the power is off or the area is safe before operation.

Shock and burn hazard: The labels on the surface or inside the device warn of possible dangerous voltages (shock hazard) and high temperatures (burn hazard), which should be observed during operation.

Equipment Compatibility and Use

Processor-Specific Disablement: Some FLEX I/O remote I/O adapters (e.g., 1794-ASB Series E, 1794-ASB2 Series D, etc.) are not compatible with the Classic PLC-5/15 or PLC-5/25 processors and may cause the remote I/O to operate abnormally.

Module Use Restrictions: In Class I Division 2 applications, only Class I Division 2 listed or approved accessories and modules for the 1794 platform may be used.

Installation and Wiring

Installation environment and method: The equipment is suitable for use in industrial environments with pollution class 2, overvoltage category II, and at altitudes up to 2000 metres above sea level, and is classified as Group 1, Class A industrial equipment. Installation is in a suitable enclosure, which is flame retardant and can only be accessed internally by means of tools. Panel mounting or DIN rail mounting is available, taking care to leave a minimum of 25mm of space around the FLEX system. Ensure correct earthing by using zinc plated yellow chrome steel DIN rails, avoiding corrosive, oxidised or poorly conductive materials (e.g. aluminium or plastics) and fix DIN rails at 200mm intervals, using end anchors where appropriate.