Siemens 6AG1138-4DF11-7AB0 — Product Overview, Technical Parameters, Applications, Advantages, and Related Models

1. Product Introduction

The Siemens 6AG1138-4DF11-7AB0 is a SIPLUS ET 200S EM 1SI RS232/422 serial communication module designed for industrial automation systems. It provides a serial communication interface for exchanging data between a compatible SIMATIC ET 200S station and external devices.

The module is based on the standard ET 200S module 6ES7138-4DF11-0AB0. Its key distinction is the SIPLUS environmental variant, which is specified for an operating temperature range of −25°C to +70°C and incorporates conformal coating.

This module is particularly useful when a PLC-based machine needs to communicate with serial equipment such as industrial instruments, barcode readers, printers, controllers, or other compatible devices. Depending on the application and configuration, communication can use RS232, RS422, or RS485-related signalling and supported protocols such as MODBUS RTU and USS.

The module is intended to operate as part of a compatible ET 200S station rather than as a standalone controller. Correct operation depends on the station configuration, serial wiring, communication settings, PLC program, and the protocol supported by the connected device.

2. Basic Product Information

The module’s dimensions refer to the body of the electronic module. The weight is approximately 50 g, excluding packaging and any separately supplied accessories.

The exact communication capability depends on the physical interface and selected operating mode. Before using the module in a particular system, confirm the required protocol, transmission rate, message format, and electrical connection.

3. Detailed Technical Parameters

3.1 Electrical and Power Specifications

The module is designed to receive power through the compatible ET 200S station. Its power requirements should be included in the station’s overall load calculation, together with the requirements of the interface module and other installed electronic modules.

The typical power loss of approximately 1.2 W is relevant when calculating cabinet heat dissipation. Adequate ventilation and suitable cabinet design help ensure reliable operation, particularly where several modules are installed close together.

3.2 Communication Interface Parameters

The RS232 and RS422 interfaces address different communication requirements. RS232 is commonly used for short-distance connections between two devices, while RS422 uses differential signalling and can be suitable for longer cable runs or electrically noisy industrial environments.

For applications using RS485-related communication, verify the precise interface arrangement supported by the module and the required wiring. Physical-layer compatibility must be established before connecting the equipment.

3.3 Communication Protocols and Data Handling

MODBUS RTU is commonly used to exchange register-based information with compatible instruments and industrial equipment. USS is associated with communication with compatible drive products.

The actual data throughput depends on the selected protocol, message size, transmission settings, external equipment, and PLC program. The module should therefore be selected according to the communication requirements of the application rather than the nominal interface type alone.

3.4 Environmental and Mechanical Parameters

The SIPLUS design provides additional environmental resistance compared with a standard module variant. However, conformal coating does not make the module waterproof or eliminate the need for an appropriate control cabinet.

The unused interfaces should remain covered as required by the product design. This helps maintain the intended environmental protection of the installed module.

4. Product Working Principle

The 6AG1138-4DF11-7AB0 provides a serial communication channel between the ET 200S automation station and a compatible external device. It transfers data from the PLC to the connected equipment and receives data that the PLC can use in its control logic.

A typical operating sequence involves the following steps.

1. Module installation: The module is installed in a compatible ET 200S station.

2. Physical interface selection: The engineer determines whether the external device requires RS232C, RS422, or another supported configuration.

3. Communication configuration: The transmission rate, data format, protocol settings, and other parameters are configured according to the external device.

4. Data transmission: The PLC program sends commands, requests, or data through the module.

5. Data reception: The module receives incoming messages from the connected equipment.

6. Data processing: The PLC program interprets the received information and uses it for monitoring, control, recording, or production sequencing.

7. Communication diagnostics: The program handles communication errors, timeouts, invalid messages, or unavailable devices according to the application’s requirements.

Reliable communication requires the module and external device to use compatible physical interfaces and matching communication settings. Correct wiring alone is not sufficient if the protocol or message format is incompatible.

5. Product Applications

5.1 Industrial Instruments and Measurement Devices

Many industrial instruments transmit measurement values through serial communication. The module can connect compatible instruments to a PLC-based control system.

Typical applications include reading measurement values, receiving operating status, transferring configuration information, and integrating serial instruments into an existing production process.

This arrangement is useful when an instrument does not provide the digital or analogue interface required by the control system but supports a compatible serial protocol.

5.2 MODBUS RTU Communication

MODBUS RTU is widely used for communication between PLCs and compatible industrial devices.

Where supported by the selected configuration, the module can exchange data with equipment that uses MODBUS RTU.

Examples include:

• Reading process values from compatible instruments.

• Retrieving status information from external devices.

• Transferring register data between equipment and a PLC.

• Integrating compatible serial devices into an established control system.

• Collecting process information for machine monitoring.

The device address, communication speed, parity, data format, and register mapping must be configured correctly. The module does not automatically translate an unsupported protocol into MODBUS RTU.

5.3 Communication with Compatible Drive Equipment

USS is used by compatible drive products for serial communication.

The module can form part of an automation arrangement in which the PLC exchanges supported commands and status information with a compatible drive.

Potential applications include sending operating commands, retrieving drive status, exchanging selected parameters, and integrating drive information into the PLC program.

The precise functions depend on the drive model and the configured communication method. The serial interface should not be treated as a substitute for a high-performance real-time motion-control network.

5.4 Barcode Readers and Identification Devices

Some barcode readers and identification devices provide serial data outputs.

The module can be considered when a compatible device must transmit product codes or status information to a PLC.

Typical applications include product identification, production tracking, package verification, and transferring scanned data into a machine sequence.

The reader’s physical interface, protocol, message format, and timing requirements must be checked before selecting the module.

5.5 Printers and Serial Terminals

Certain industrial printers and terminals support serial communication.

The module may be used to exchange data with compatible equipment where serial transmission is supported by both the device and the automation configuration.

Applications can include sending production information, transferring identifiers, or integrating a serial terminal into an existing machine-control system.

The required data format and transmission timing should be verified, particularly when the equipment is used in a high-throughput production environment.

5.6 Legacy Equipment Integration

Established industrial machines often contain serial devices that remain functional even when the surrounding automation system is being updated.

The module can help retain compatible equipment within an existing ET 200S architecture, reducing the need to replace every device during a retrofit.

This is useful for older measurement instruments, serial controllers, identification devices, and other industrial equipment with documented communication protocols.

5.7 Production Data Collection

The module can provide a communication path for collecting operating information from compatible external devices.

Depending on the connected equipment, this may include process measurements, device status, operating parameters, or production-related data.

The PLC can then use the received information for alarms, monitoring, process coordination, or data recording.

6. Main Product Advantages

6.1 Flexible Serial Connectivity

The module supports serial communication using the interface options associated with its RS232/422 designation. This allows it to connect compatible equipment that may not support the same communication method as newer network-based devices.

6.2 Support for Industrial Communication Protocols

Support for MODBUS RTU and USS makes the module relevant to applications involving compatible instruments and drive equipment.

Using an appropriate protocol can simplify the exchange of commands, status values, and process data between the PLC and an external device.

6.3 Compact Design

The module occupies approximately 15 mm of width in a compatible ET 200S station.

This is useful in compact control cabinets where communication functions must be added without allocating a large amount of additional rail space.

6.4 SIPLUS Environmental Protection

The specified operating temperature range of −25°C to +70°C and the conformal coating are key features of this SIPLUS variant.

These characteristics can be advantageous in industrial installations that experience wider temperature variations or specified environmental stresses.

The complete installation must still comply with the module’s environmental limits and use an appropriate enclosure.

6.5 Integration with Existing ET 200S Systems

The module is designed for a compatible SIMATIC ET 200S station.

For a plant already using this platform, it can provide serial communication without requiring the entire distributed-I/O arrangement to be redesigned.

Compatibility with the existing station, configuration software, and PLC program must still be confirmed.

6.6 Support for Equipment Modernization

The module can be useful when an established machine needs to communicate with external serial equipment while retaining much of its existing hardware.

This can make staged modernization more practical than replacing the entire system at once.

6.7 Centralized Data Processing

Data received through the serial interface can be processed in the PLC program and used alongside other machine signals.

This allows serial equipment to participate in the broader automation sequence rather than operating as an isolated device.

6.8 Low Weight and Small Footprint

With an approximate weight of 0.050 kg, the module is lightweight and compact.

Its small size can simplify installation and replacement within a compatible station.

6.9 Defined Communication Role

A dedicated serial module gives the system a clear hardware interface for communication with external equipment.

When the protocol, wiring, and program logic are documented properly, this can help maintenance personnel identify the source of communication problems more efficiently.

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

The following models are related to the ET 200S/SIPLUS range. They cover the closest serial communication alternatives and other functional modules used in compatible distributed-I/O systems.

The first model, 6ES7138-4DF11-0AB0, is the closest comparison because it is the standard counterpart of the main SIPLUS model.

The other two serial modules are related alternatives, but their exact interface capabilities should be checked before selecting them. The counter and pulse-generator modules serve different functions and are not direct replacements for a serial communication module.

Selection Guidance

– Choose 6ES7138-4DF11-0AB0 when comparing the standard environmental version of the same RS232/422 serial module.

– Consider 6AG1138-4DF01-7AB0 when a related SIPLUS serial interface is required, but confirm the precise interface and protocol configuration.

– Consider 6ES7138-4DF01-0AB0 when a standard serial interface module matches the application’s requirements.

– Choose 6AG1138-4DA04-2AB0 for pulse counting and measurement rather than serial data exchange.

– Choose 6AG1138-4DD01-7AB0 when the application needs pulse-generation and timer functions.

The listed dimensions and weights for the compact ET 200S modules are nominal module-body values. Confirm them against the exact hardware revision before ordering.

8. Five Popular Siemens Automation Models

The following models represent common product categories used in industrial automation. They are complementary components for PLC-based systems rather than direct replacements for the main serial communication module.

These products perform different functions within an industrial automation system.

A PLC executes the control program and coordinates machine operations. A distributed-I/O interface connects field modules to the controller. A power supply provides the required DC power, while an HMI provides operators with access to machine status, alarms, and operating controls.

Dimensions and weights vary with hardware revision and configuration. Where exact mechanical values have not been confirmed, they are marked for verification rather than replaced with estimates.

9. Comparison of the Main Model and Its Standard Counterpart

The main distinction is the environmental design. The SIPLUS variant is designed for a wider specified operating temperature range and incorporates conformal coating.

Although the two models are closely related, they should not be substituted without checking the complete ordering code, electrical characteristics, communication configuration, and station compatibility.

10. Installation and Maintenance Considerations

10.1 Check the Physical Interface

Confirm that the connected equipment supports the interface selected for the module. The cable wiring and signal assignments must match both ends of the connection.

10.2 Match Communication Parameters

Set the communication speed, data format, protocol, and addressing parameters according to the external device.

If communication fails, check the settings on both devices before assuming that the module is defective.

10.3 Use Suitable Industrial Cabling

Choose a suitable cable for the selected serial interface and expected transmission distance.

Grounding, shielding, cable routing, and separation from sources of electrical interference are important for reliable communication.

10.4 Plan for Communication Faults

The PLC program should handle communication timeouts, invalid messages, and unavailable devices.

The correct response depends on the machine. Some applications may require an alarm, while others may need to stop a process or move the equipment into a defined safe state.

10.5 Maintain Environmental Protection

Keep the module within its specified operating temperature range and install it in a suitable enclosure.

The conformal coating provides additional environmental protection, but the complete station still requires appropriate cabinet design and protection against unsuitable exposure.

10.6 Consider Product Lifecycle

ET 200S is an established automation platform. For an existing installation, verify spare-part availability and the compatibility of the replacement module with the installed hardware and software.

For a new design, compare the long-term maintenance costs of retaining ET 200S with those of adopting a newer distributed-I/O platform.

11. Final Recommendation

The Siemens 6AG1138-4DF11-7AB0 is a SIPLUS ET 200S EM 1SI RS232/422 serial communication module designed to connect compatible serial equipment to a distributed automation system.

Its main characteristics include a single serial communication interface, a 24 V DC supply arrangement, approximately 1.2 W typical power loss, an operating temperature range of −25°C to +70°C, a module size of 15 × 81 × 52 mm, and an approximate weight of 0.050 kg.

Its main advantages are its compact size, serial communication capabilities, integration with compatible ET 200S stations, and SIPLUS environmental design.

For a direct alternative, 6ES7138-4DF11-0AB0 is the first model to compare. Other serial modules may be appropriate when the required interface differs, while the counter and pulse-generator models should be considered only for their respective functions.

Before purchasing or replacing the module, confirm the exact ordering code, interface type, supported protocol, transmission settings, electrical requirements, dimensions, weight, and compatibility with the existing automation station.