Siemens 6AG1138-4FB04-2AB0 — Detailed Product Profile and Technical Specifications

1. Product Overview

The Siemens 6AG1138-4FB04-2AB0 is a SIPLUS ET 200S fail-safe digital output module designed to switch safety-related loads in compatible industrial automation systems. It provides four fail-safe digital outputs operating with a nominal 24 V DC load supply, with a specified switching capability of up to 2 A per channel.

The module is intended for applications in which the control system must do more than switch an ordinary output. It can form part of a safety-related control function used to place machinery or equipment into a defined safe state when a protective device is activated or a fault is detected.

This SIPLUS version is based on the standard module 6ES7138-4FB04-0AB0 and includes conformal coating and a specified operating temperature range of -25°C to +60°C.

One important procurement detail is that this model is a legacy product whose standard catalog lifecycle has been marked as discontinued. It may still be relevant for maintenance, replacement, and existing ET 200S installations, but its suitability for a new project should be evaluated against current hardware options and long-term support requirements.

2. Technical Parameters

The following tables summarize the principal electrical, mechanical, functional, and environmental characteristics.

2.1 General specifications

The technical documentation gives a module weight of approximately 85 g, equivalent to 0.085 kg. Catalog logistics data may list a net weight of approximately 0.092 kg. For engineering records, the two values should not be treated as conflicting electrical specifications: use the exact catalog or physical-product record required by your inventory system.

2.2 Electrical specifications

The rated current is an important selection parameter, but it should not be interpreted as permission to connect any load drawing up to 2 A. The load’s startup current, inductive characteristics, wiring, switching frequency, and the module’s permitted operating conditions must all be checked.

2.3 Mechanical dimensions and weight

The 30 mm width is useful in compact distributed I/O assemblies. The dimensions shown here refer to the electronic module itself rather than the complete station, terminal modules, interface hardware, or enclosure.

2.4 Environmental specifications

The conformal coating is intended to improve resistance to selected environmental stresses. It does not make the module waterproof or suitable for unrestricted outdoor exposure, immersion, or every corrosive atmosphere.

2.5 Safety and functional characteristics

Safety ratings apply to the module in the appropriate configuration and do not guarantee that the complete installation automatically achieves SIL 3, PL e, or Category 4. The entire safety function must be designed and validated to the applicable requirements.

3. Product Introduction

3.1 What is the 6AG1138-4FB04-2AB0?

The 6AG1138-4FB04-2AB0 is a fail-safe digital output module in the SIPLUS ET 200S product family. Its purpose is to control compatible electrical loads as part of a safety-related automation system.

Unlike an ordinary digital output module, which is primarily intended to switch devices on and off according to a standard PLC program, a fail-safe output module participates in a defined safety function. It receives safety-related commands through a supported safety communication arrangement and switches its outputs according to the configured safety logic.

The module provides four fail-safe digital outputs. Each output is designed for a nominal 24 V DC load supply, with a rated current of 2 A per channel under the specified operating conditions.

Typical loads include compatible contactors, solenoid valves, indicator devices, and other industrial actuators that need to be switched as part of a safety-related process.

3.2 How the module works

The module is installed in a compatible ET 200S distributed I/O station. A suitable interface module connects the station to the automation network, while a compatible fail-safe controller executes the safety program.

The general operating sequence is as follows:

1. Safety devices, sensors, and interlocks provide information about the machine’s operating condition.

2. The fail-safe controller evaluates these signals against the configured safety logic.

3. The controller transmits the required output state through the supported safety communication arrangement.

4. The output module switches the appropriate channel or channels to control the connected loads.

5. If a safety condition or supported fault response requires a shutdown, the safety system drives the relevant outputs to their defined safe state.

The safe state depends on the application. For many machines, it means removing electrical power from a hazardous actuator. Some applications require a different response, so the safety design must define the appropriate state for every relevant fault or operating condition.

3.3 Role in a distributed I/O system

Distributed I/O makes it possible to locate signal modules near the machinery they control rather than bringing every field cable back to a central PLC cabinet.

The ET 200S platform uses a modular arrangement in which the interface hardware, terminal components, and electronic modules form a station. The station can be organized around a production cell, conveyor section, packaging machine, or other equipment group.

Within this arrangement, the 6AG1138-4FB04-2AB0 handles fail-safe output functions. It is especially relevant when safety-related switching needs to be located near the equipment and integrated into a compatible safety network.

3.4 Difference between F-DQ and ordinary digital outputs

The designation F-DQ identifies a fail-safe digital output function. This is different from a standard digital output, which may be used for ordinary sequence control, status lamps, or non-safety-related solenoids.

A standard digital output is not an equivalent replacement for this model when the application depends on a safety-related shutdown function.

3.5 Purpose of the SIPLUS design

The SIPLUS variant is designed for applications that require additional environmental protection compared with the corresponding standard product.

The 6AG1138-4FB04-2AB0 uses conformal coating and has a specified operating temperature range of -25°C to +60°C. These characteristics can be useful in industrial installations where environmental conditions are more demanding than those found in a clean, temperature-controlled cabinet.

The coating does not eliminate the need to protect the module from unsuitable exposure. Proper enclosure selection, condensation management, wiring protection, and compliance with the installation instructions remain necessary.

4. Typical Applications

4.1 Emergency-stop circuits

Emergency-stop devices are used on production machines, packaging systems, conveyor installations, and automated handling equipment.

The module can be used as part of a compatible safety system that switches designated loads when an emergency-stop condition is detected. For example, the safety controller may command the output to de-energize a contactor that removes power from a hazardous drive.

The module is only one element of the overall safety function. The emergency-stop device, input system, safety program, contactors, feedback monitoring, and stopping behavior must all be considered together.

4.2 Safety-door and guard interlocks

Industrial machines often have access doors, movable guards, protective covers, or interlocked maintenance panels.

When a guard is opened, the safety controller may need to stop hazardous motion or prevent the machine from starting. The 6AG1138-4FB04-2AB0 can switch compatible output loads as part of the resulting safety action.

Typical applications include enclosed assembly stations, machining equipment, robotic cells, automated test equipment, and packaging machines.

4.3 Robotic cells

Robotic systems often contain several safety-related devices, including access gates, emergency-stop buttons, protective sensors, and interlocks.

A fail-safe output module can be used to control compatible external devices involved in a safety function. Examples include switching a safety contactor or commanding a supported safety-related actuator arrangement.

The module does not independently provide complete robot safety. The robot controller, safety controller, protective equipment, stopping mechanisms, and overall machine design must meet the required safety standards.

4.4 Conveyor systems

Large conveyor installations may have many separate operating zones, each with its own protective devices and stopping requirements.

Distributed I/O can help organize these functions by placing control modules near the relevant equipment. The fail-safe outputs can be assigned to supported shutdown devices or other compatible safety-related loads.

Applications include warehouse conveyors, sorting systems, assembly-line transfer stations, pallet handling equipment, and automated material movement.

4.5 Packaging and production machinery

Packaging machines may contain cutters, sealing units, moving belts, pneumatic mechanisms, and other equipment that requires protective interlocks.

A fail-safe output module can participate in the controlled shutdown of compatible actuators when a safety condition occurs. The actual output assignment depends on the machine’s safety architecture and the electrical characteristics of each load.

The four-channel arrangement may be useful where several independent safety-related output commands are required within one ET 200S station.

4.6 Pneumatic and hydraulic control systems

Some industrial machines use solenoid valves to control pneumatic or hydraulic mechanisms. Where a valve is part of a defined safety function, its electrical control may need to be integrated into a fail-safe system.

The module can be considered for compatible 24 V DC loads within its specified current and switching limits.

Valve selection requires particular care. The designer must consider coil current, inductive switching behavior, residual energy, valve failure modes, and whether de-energizing the valve actually produces the intended safe state.

4.7 Industrial machinery operating in demanding environments

The conformal coating and specified temperature range make this SIPLUS module relevant to selected industrial environments where environmental resistance is an important design consideration.

Potential applications include machinery in industrial processing areas, production facilities with airborne contaminants, and control cabinets exposed to temperature fluctuations.

The environmental classification must be compared with the actual site conditions. A coated module should not be assumed to tolerate every chemical, high-humidity condition, or direct exposure to liquids.

4.8 Existing ET 200S safety installations

This model is particularly relevant to the maintenance of existing ET 200S installations.

If a machine was originally designed around the 6AG1138-4FB04-2AB0, retaining the same model may reduce the need for hardware changes and help preserve the existing configuration.

Because the model is a legacy product, availability and lifecycle status should be considered during maintenance planning. A replacement should be confirmed against the original configuration rather than selected solely on the basis of a similar product description.

5. Product Advantages

5.1 Four fail-safe output channels

The module offers four safety-related digital output channels in one compact electronic module.

This allows multiple output commands to be organized within a single station, reducing the need to distribute every safety-related output across separate modules. The actual channel assignment depends on the application and safety configuration.

5.2 Rated 24 V DC operation

The 24 V DC load supply is commonly used in industrial control cabinets and automation equipment.

This makes the module relevant to compatible systems that use 24 V DC contactors, valves, and other industrial loads. The supply voltage, load current, and protection requirements must still be checked for every connected device.

5.3 Up to 2 A per output channel

The specified rated current of 2 A per channel provides capacity for a range of compatible industrial loads.

It is important to distinguish rated current from startup current and switching capacity. A load that draws less than 2 A during normal operation may still exceed the permitted conditions when energized or switched off.

5.4 Short-circuit protection

Short-circuit protection is specified for the digital outputs. This can help protect the output circuitry under supported fault conditions and assist with fault management.

It does not replace correct circuit protection, appropriate cable sizing, or proper installation. The documented protective behavior and response to faults must be understood before the module is incorporated into a safety design.

5.5 PROFIsafe integration

PROFIsafe enables safety-related communication within compatible automation architectures.

This can help integrate the module into a coordinated safety system rather than requiring every safety-related output to be controlled independently through conventional wiring and standard logic.

The communication arrangement must use compatible safety hardware, engineering configuration, and validated safety parameters.

5.6 Environmental protection through conformal coating

The SIPLUS version has conformal coating intended to improve resistance to selected environmental influences.

This can be an advantage in industrial cabinets exposed to environmental stresses that are covered by the product’s specifications. It is still necessary to follow the permitted humidity, temperature, and installation conditions.

5.7 Extended operating temperature range

The specified operating range of -25°C to +60°C provides more flexibility than many conventional indoor automation environments require.

This may be useful when the equipment is installed in facilities with lower ambient temperatures or warmer operating conditions. The actual temperature at the module should be considered, including the heat generated by neighboring equipment.

5.8 Compact 30 mm width

The module has a width of 30 mm and dimensions of 30 × 81 × 52 mm.

The compact form factor can help keep distributed I/O assemblies organized and reduce the physical space needed for the electronic module itself. Complete station planning must also include terminal components, wiring space, and maintenance access.

5.9 Support for demanding safety applications

The module is specified for applications with capability up to SIL 3, Performance Level e, and Category 4 under the applicable standards and system conditions.

This makes it a potential component in high-integrity safety functions. The safety level achieved by the finished machine depends on the entire safety-related control system, including sensors, controller, actuators, wiring, diagnostics, and validation.

5.10 Useful for maintaining installed machinery

For a plant already using ET 200S fail-safe modules, the model can be useful for maintaining the original system design.

Matching the original model may reduce engineering changes, help preserve existing cabinet layouts, and simplify the process of verifying hardware compatibility.

Since the product is a legacy item, spare-parts planning should include the availability of suitable replacements and the feasibility of a controlled migration to a newer platform.

6. Brand and Product Series

6.1 Siemens

Siemens is an industrial automation brand whose portfolio includes programmable controllers, distributed I/O, drives, industrial networking, operator interfaces, and related control equipment.

For this product, the relevant area is the SIMATIC automation platform and its safety-related distributed I/O hardware.

6.2 SIPLUS

SIPLUS identifies a product range designed for selected applications requiring enhanced environmental characteristics.

The precise benefits depend on the model. For the 6AG1138-4FB04-2AB0, the main characteristics are conformal coating and the specified -25°C to +60°C operating range.

6.3 ET 200S

ET 200S is a modular distributed I/O series used to connect field signals and actuators to compatible automation systems.

The family includes standard signal modules, communication-related modules, fail-safe electronic modules, and other components that form distributed stations.

The 6AG1138-4FB04-2AB0 belongs to the fail-safe electronic module group. Its purpose is to switch supported loads as part of a safety-related control function, rather than perform ordinary general-purpose output switching.

7. Five Related Models in the Same Series or Functional Group

The following models are useful for comparison when maintaining an ET 200S installation or planning a safety-related I/O arrangement.

The standard counterpart, 6ES7138-4FB04-0AB0, is the closest technical comparison. The other models provide related input, combined I/O, or relay-output functions, but they are not direct replacements for the four-channel fail-safe transistor output module.

How to choose between these related models

– Choose the standard counterpart when the required output function is the same and the environmental specification of the standard module is suitable for the installation.

– Choose a fail-safe input module when the system needs to acquire safety-related signals rather than switch loads.

– Consider a combined input/output module when the application requires both functions and the available channels and configuration meet the safety requirements.

– Consider a relay-output model only when its switching characteristics, electrical ratings, response behavior, and safety capability are appropriate for the connected load.

The dimensions and weights marked for verification should be confirmed from the exact model documentation before using them in a bill of materials or replacement plan.

8. Five Popular Siemens Models for Industrial Automation

The models below are widely recognized products from the broader Siemens automation portfolio. They are included as related purchasing and system-planning references, not as direct substitutes for the 6AG1138-4FB04-2AB0.

8.1 SIMATIC S7-1200 CPU

The S7-1200 series is commonly used in compact machines and smaller automation systems. It provides programmable control functions and supported communication interfaces for integrating field equipment.

When used alongside safety-related equipment, the selected controller and architecture must be appropriate for the intended safety functions. A standard PLC cannot be assumed to replace a fail-safe controller.

8.2 SIMATIC S7-1500 CPU

The S7-1500 series is intended for more demanding control tasks and larger or more complex automation applications.

It may be relevant when planning a new control system or modernization project. The precise CPU model, safety capabilities, communication interfaces, and engineering requirements must be matched to the project.

8.3 SIMATIC ET 200SP interface module

ET 200SP is another distributed I/O platform. It can be considered for new installations or modernization where a different station architecture is appropriate.

ET 200SP modules and ET 200S modules are not automatically interchangeable. A migration requires checking the interface hardware, signal modules, terminal components, engineering configuration, wiring, and safety requirements.

8.4 SITOP power supply

A suitable 24 V DC supply is essential for many industrial automation systems.

The power supply must support the total connected load, including startup current, actuator demand, and any design margin required by the application. Protective functions and power-distribution arrangements should be selected to suit the control cabinet and equipment.

8.5 SIMATIC HMI Basic Panel

An HMI panel gives operators access to machine status, alarm information, process displays, and supported operating commands.

It can complement a PLC and distributed I/O installation, but it is not a replacement for safety logic or fail-safe output hardware. Any operator command affecting machine operation must be handled by the appropriate control and safety architecture.

9. Installation and Engineering Considerations

9.1 Confirm the supply voltage and load current

The module is designed for 24 V DC loads, with a rated output current of 2 A per channel.

Before connecting a load, confirm its normal current, startup current, inrush behavior, and inductive characteristics. The module’s specified switching limits and wiring requirements must be observed.

9.2 Check the interface and safety controller

The module must be used in a supported ET 200S configuration with compatible safety hardware and PROFIsafe engineering.

The interface module, controller, software version, and configuration must all support the intended arrangement. A physically compatible module is not necessarily compatible with every existing safety project.

9.3 Verify the safe state of each output

A safe state is determined by the machine’s risk assessment and the required safety function.

For one actuator, removing power may be appropriate. For another, a controlled sequence or additional monitoring may be necessary. The designer must verify that the connected device and the complete control arrangement produce the required safe behavior.

9.4 Observe inductive-load limitations

Contactors and solenoid valves are inductive loads. When their current is switched off, the resulting voltage transient can affect the output circuit.

Use compatible loads and follow the module’s specified electrical limits. Any required suppression components must be selected in accordance with the load and safety design.

9.5 Maintain environmental protection

The conformal coating provides additional protection, but the module still has defined operating limits.

Keep the module within its specified temperature range, avoid prohibited condensation conditions, and leave the required connector covers in place on unused interfaces. The control cabinet should be suitable for the actual dust, humidity, chemical exposure, and temperature conditions.

9.6 Consider the product lifecycle

The 6AG1138-4FB04-2AB0 is a legacy model with a discontinued catalog lifecycle status.

For an existing installation, it may remain relevant as a maintenance or spare-parts item. For a new project, evaluate the long-term availability of the module, the feasibility of a supported replacement, and the engineering effort involved in moving to a newer platform.

A replacement should not be selected on dimensions or nominal voltage alone. It must meet the required output function, current ratings, communication requirements, environmental conditions, and safety performance.

10. Final Product Summary

The Siemens 6AG1138-4FB04-2AB0 is a SIPLUS ET 200S fail-safe digital output module designed to switch compatible industrial loads as part of a safety-related automation system.

Its main characteristics include four fail-safe transistor outputs, a nominal 24 V DC load supply, a rated output current of 2 A per channel, PROFIsafe integration, conformal coating, and a specified operating temperature range of -25°C to +60°C.

The module has dimensions of 30 × 81 × 52 mm and a physical weight of approximately 0.085 kg, while the catalog net weight is listed at approximately 0.092 kg.

Its main advantages are the compact four-channel design, support for safety-related output switching, specified short-circuit protection, environmental coating, and integration with compatible ET 200S safety architectures.

The closest comparison is the standard module 6ES7138-4FB04-0AB0. Other related models can provide fail-safe inputs, combined I/O, or relay outputs, but their functions and electrical characteristics differ.

For an existing machine, matching the original hardware is often the simplest starting point. For a new installation or modernization, the decision should also account for product lifecycle, replacement availability, safety-system compatibility, environmental conditions, and the validation requirements of the complete machine.