Product Overview

The Siemens 6AG1972-0DA00-2AA0 SIPLUS DP Active RS-485 Terminating Resistor is an active bus termination device designed for PROFIBUS DP communication networks. It helps maintain stable signal transmission by providing the required electrical termination at the end of an RS-485 bus segment.

This component belongs to the Siemens SIPLUS product family and is based on the standard SIMATIC DP terminating element, 6ES7972-0DA00-0AA0. The SIPLUS version incorporates conformal coating and an extended operating temperature range, making it suitable for industrial environments where environmental conditions may be more demanding than those found in conventional control cabinets.

PROFIBUS DP is widely used in industrial automation to exchange process data between programmable logic controllers, remote I/O stations, drives, and other field devices. Reliable communication depends on correct cable installation, network topology, grounding, and bus termination. The 6AG1972-0DA00-2AA0 supports this infrastructure by providing an active RS-485 termination point.

The device operates from a 24 V DC supply, with a typical current consumption of approximately 30 mA. It supports PROFIBUS DP transmission rates from 9.6 kbit/s to 12 Mbit/s. Its screw-terminal connections provide a practical method for connecting the power supply and PROFIBUS bus conductors.

The SIPLUS version is specified for an operating temperature range of -25°C to +60°C. Its conformal coating provides additional protection for electronic components against certain environmental influences. This makes it relevant to process automation, manufacturing facilities, and industrial installations where reliable fieldbus communication is essential.

Technical Specifications

Technical specifications should be checked against the product label and applicable Siemens documentation before installation.

Function and Working Principle

The 6AG1972-0DA00-2AA0 performs an important electrical function in PROFIBUS DP communication networks. Its primary purpose is to provide active RS-485 bus termination, helping maintain signal quality and reducing communication problems associated with improper line termination.

1. PROFIBUS DP Signal Termination

PROFIBUS DP commonly uses an RS-485 physical layer for communication between automation devices. Electrical signals travel along the bus cable, and impedance mismatches at cable ends can cause signal reflections.

These reflections may interfere with the transmitted data and contribute to communication errors, particularly at higher transmission speeds or when cable lengths and network configurations are not correctly managed.

A termination device provides the electrical conditions required at the end of the bus segment. The 6AG1972-0DA00-2AA0 is designed to perform this function as an active terminating element.

2. Active RS-485 Termination

Unlike a simple passive resistor, an active termination device requires an external power supply to maintain its termination function.

The 6AG1972-0DA00-2AA0 uses a 24 V DC supply. This allows the termination circuit to maintain the required electrical conditions for the PROFIBUS RS-485 bus.

Because the device requires external power, engineers must verify that the supply remains available whenever the bus termination is needed. An interrupted termination supply may affect communication stability.

3. High-Speed PROFIBUS Communication

The device supports transmission rates up to 12 Mbit/s, covering the commonly used PROFIBUS DP speed range from 9.6 kbit/s to 12 Mbit/s.

Correct termination becomes particularly important as communication speeds increase. Cable characteristics, network layout, connectors, and grounding all influence the electrical quality of an RS-485 segment.

The terminating element helps maintain the physical-layer conditions required for dependable data exchange.

4. Conformal Coating Protection

The SIPLUS version includes conformal coating on its electronic assemblies. This coating provides additional protection against certain environmental influences that may affect electronic components.

It is particularly relevant in industrial process environments where temperature variations, humidity, and selected chemically active substances may be present.

Conformal coating does not make the device waterproof or suitable for unrestricted exposure to corrosive chemicals. The installation must remain within the specified environmental and protection limits.

5. Communication Stability

The device contributes to the electrical stability of a PROFIBUS DP segment by providing the intended termination at the network endpoint.

Correct termination can help reduce signal reflections, improve communication reliability, and support consistent data exchange between connected automation devices.

It should be installed as part of a properly designed bus topology rather than used as a general-purpose signal amplifier or network repeater.

Role in Industrial Automation Systems

The Siemens 6AG1972-0DA00-2AA0 is a supporting component within PROFIBUS DP communication infrastructure. Although it does not perform PLC processing or field I/O functions, it helps maintain the electrical conditions needed for reliable communication.

PLC Communication

Programmable logic controllers exchange information with remote I/O stations, drives, and other automation devices through industrial communication networks.

In a PROFIBUS DP system, the terminating element helps maintain the electrical integrity of the bus segment. This supports reliable communication between the controller and connected field devices.

Remote I/O Networks

Distributed I/O stations are commonly installed near sensors and actuators to reduce long individual wiring runs back to the main control cabinet.

These stations may communicate with a central PLC through PROFIBUS DP. Correct termination at the bus segment endpoints helps reduce communication disturbances and supports stable data exchange.

Drive Communication

Industrial drives can receive operating commands and transmit status information through PROFIBUS DP when equipped with compatible communication interfaces.

The 6AG1972-0DA00-2AA0 can support the communication infrastructure in networks containing drives, controllers, and other field devices.

Process Automation

Process plants often use distributed automation equipment across large operating areas. Stable communication is essential for monitoring measurements, exchanging control commands, and coordinating equipment operation.

The SIPLUS terminating element can be used in suitable PROFIBUS installations where its environmental specifications are required.

Industrial Applications

The 6AG1972-0DA00-2AA0 is intended for PROFIBUS DP network termination rather than direct control of motors, valves, or other field equipment.

1. Manufacturing Automation

Manufacturing lines frequently use PROFIBUS DP to connect PLCs, remote I/O stations, drives, and machine controllers.

The terminating element can be installed at the appropriate bus endpoint to help maintain signal quality and reliable communication during production.

2. Process Control Systems

Chemical processing, water treatment, and other process industries often use distributed control equipment connected through industrial fieldbus networks.

The SIPLUS conformal coating and extended temperature range make this version relevant to installations requiring additional environmental protection.

3. Distributed I/O Systems

Remote I/O networks allow sensors and actuators to communicate with central controllers through a shared fieldbus.

Correct termination helps maintain the electrical characteristics of the network and reduces the risk of communication errors caused by signal reflections.

4. Industrial Drive Systems

Variable frequency drives and other motor-control equipment may exchange control and diagnostic data over PROFIBUS DP.

The terminating element supports the physical communication network connecting these devices, helping maintain dependable data transmission.

5. Industrial Utility Facilities

Water distribution, wastewater treatment, power utilities, and other infrastructure facilities may use PROFIBUS-based automation systems.

In these applications, stable communication is important for remote monitoring, equipment coordination, and process supervision.

6. Harsh Industrial Environments

Some industrial facilities experience temperature changes, humidity, dust, or chemically active environmental conditions.

The SIPLUS version is designed with additional environmental protection compared with its standard base model. Its actual suitability must still be assessed against the installation environment and applicable specifications.

Installation and System Integration

Correct installation is essential because the 6AG1972-0DA00-2AA0 performs a physical-layer function in the PROFIBUS network.

1. Select the Correct Bus Location

The active terminating element should be installed at the appropriate endpoint of the PROFIBUS DP segment according to the network design.

PROFIBUS RS-485 networks require correct termination at both ends of a bus segment. Additional termination points or incorrect placement may interfere with communication.

Engineers should review the network topology before connecting the device.

2. Provide the Required 24 V DC Supply

The device requires a nominal 24 V DC supply, with a permissible range of 20.4–28.8 V DC.

The power supply must remain available whenever the termination function is required. A supply interruption can affect the electrical termination of the bus and may lead to communication problems.

Verify polarity, terminal assignments, and supply stability before commissioning.

3. Connect PROFIBUS Conductors

The PROFIBUS cable conductors are connected through the device’s screw terminal block.

Observe the correct conductor assignments and maintain the required cable polarity. Incorrect wiring may prevent communication or cause intermittent network faults.

Use appropriate cable preparation and tightening practices to ensure secure electrical connections.

4. Maintain Proper Shielding and Grounding

RS-485 communication networks are sensitive to electrical interference and grounding arrangements.

Follow the PROFIBUS installation guidelines for cable shielding, equipotential bonding, and grounding. Avoid unnecessary changes to the cable route and keep communication wiring away from strong sources of electromagnetic interference where practical.

5. Verify Transmission Rate

The device supports PROFIBUS DP transmission rates up to 12 Mbit/s.

The configured network speed must be compatible with all connected devices and the cable installation. Cable length, network topology, and transmission rate should be evaluated together.

6. Inspect Environmental Conditions

The SIPLUS device is specified for operation from -25°C to +60°C and has an IP20 protection rating.

Install it in a suitable enclosure or protected location. Although conformal coating offers additional environmental protection, the component should not be exposed directly to water or conditions outside its specified limits.

7. Commission and Test the Network

After installation, verify the 24 V DC supply, terminal connections, bus polarity, and termination location.

Check the network using appropriate PROFIBUS diagnostic tools. Confirm that connected devices can communicate reliably and that no persistent bus errors or station faults are present.

Compatible System Components

The 6AG1972-0DA00-2AA0 can be used with compatible Siemens SIMATIC and PROFIBUS DP equipment as part of a correctly engineered network.

Compatibility depends on the complete PROFIBUS network design. The terminating element does not replace a repeater, PLC interface, or field device.

Alternative Models and Replacement Considerations

When replacing the 6AG1972-0DA00-2AA0, it is important to distinguish between the SIPLUS version and its standard SIMATIC base model.

A standard 6ES7972-0DA00-0AA0 may be considered when replacing the SIPLUS model in a suitable environment, but it does not automatically provide the same environmental protection.

Before ordering a replacement, verify:

• The complete Siemens article number.
• Whether an active or passive termination arrangement is required.
• The required 24 V DC supply.
• The PROFIBUS transmission rate.
• The network endpoint and topology.
• The environmental temperature range.
• The need for conformal coating.
• The connection method and terminal arrangement.

A repeater, bus connector, and terminating element perform different functions. They should not be substituted for one another without reviewing the network design.

Key Advantages

Active RS-485 Termination

The device provides active termination for compatible PROFIBUS DP bus segments, helping maintain the required electrical conditions for communication.

Support for High-Speed PROFIBUS DP

With a maximum supported transmission rate of 12 Mbit/s, the device is suitable for compatible PROFIBUS DP networks operating across the specified speed range.

24 V DC Operation

The 24 V DC supply arrangement supports integration into common industrial control power systems.

SIPLUS Environmental Protection

Conformal coating provides additional protection for electronic components against selected environmental influences.

Extended Operating Temperature

The specified operating range of -25°C to +60°C supports installations exposed to wider temperature variations than standard indoor control environments.

Compact Installation

The compact 60 × 70 × 43 mm dimensions allow installation in suitable industrial control cabinets and communication enclosures.

Siemens SIMATIC Compatibility

Based on the standard 6ES7972-0DA00-0AA0, the product belongs to the Siemens PROFIBUS infrastructure family and can be integrated into suitable SIMATIC automation systems.

Technical FAQs

1. What is the Siemens 6AG1972-0DA00-2AA0?

It is a SIPLUS DP active RS-485 terminating element designed for PROFIBUS DP communication networks. Its primary function is to provide electrical termination at the appropriate end of a bus segment.

2. Is the 6AG1972-0DA00-2AA0 a passive resistor?

No. It is an active termination device that requires an external 24 V DC power supply. It should not be treated as an ordinary standalone passive resistor.

3. What is the rated supply voltage?

The nominal supply voltage is 24 V DC, with a permissible operating range of 20.4–28.8 V DC.

4. What is its typical current consumption?

The typical current consumption is approximately 30 mA.

5. What communication protocol does it support?

It is designed for PROFIBUS DP communication using the RS-485 physical layer.

6. What is the maximum transmission speed?

The supported transmission rate ranges from 9.6 kbit/s to 12 Mbit/s, with a maximum of 12 Mbit/s.

7. What is the difference between 6AG1972-0DA00-2AA0 and 6ES7972-0DA00-0AA0?

The 6AG1972-0DA00-2AA0 is the SIPLUS version based on the standard 6ES7972-0DA00-0AA0. The SIPLUS version includes conformal coating and an extended specified operating temperature range.

8. Can this device be used with Siemens S7 PLC systems?

It can be used in compatible PROFIBUS DP networks connected to Siemens S7 controllers, provided the controller has a suitable PROFIBUS interface and the network is correctly configured.

9. Why is active termination important?

Active termination helps maintain the electrical characteristics of the RS-485 bus. It reduces signal reflections and supports reliable communication, particularly in networks operating at higher transmission speeds.

10. What should be checked before purchasing this product?

Confirm the complete article number, product condition, 24 V DC supply requirement, PROFIBUS compatibility, terminal condition, and environmental specifications. For replacement projects, also verify whether the original installation requires the SIPLUS environmental protection features.

Procurement and Maintenance Recommendations

When purchasing the Siemens 6AG1972-0DA00-2AA0, verify the full article number and distinguish it from the standard 6ES7972-0DA00-0AA0. Although the products share a functional basis, their environmental specifications are not identical.

For new, used, or surplus equipment, inspect the enclosure, terminal blocks, identification label, and visible condition of the electronic assembly. Confirm that the device has not suffered damage from excessive heat, moisture, or improper handling.

During installation, maintain a stable 24 V DC supply and ensure that the terminating element is placed at the correct bus endpoint. Check cable polarity, shielding, grounding, and the network’s overall termination arrangement.

For maintenance, investigate recurring PROFIBUS communication faults by checking the complete bus segment rather than replacing the terminating element automatically. Cable damage, incorrect topology, missing termination power, loose terminals, and grounding problems can all contribute to communication instability.

Keep a record of the network layout, device locations, transmission rate, and power-supply arrangement. This information helps maintenance engineers identify faults and restore communication more efficiently.

Conclusion

The Siemens 6AG1972-0DA00-2AA0 SIPLUS DP Active RS-485 Terminating Resistor is an industrial communication component designed to support reliable PROFIBUS DP network operation. Based on the standard 6ES7972-0DA00-0AA0, it provides active bus termination, operates from a 24 V DC supply, and supports transmission rates up to 12 Mbit/s.

Its conformal coating and -25°C to +60°C operating temperature specification make it suitable for selected industrial environments requiring additional environmental protection. For PROFIBUS maintenance, system integration, and spare-parts procurement, accurate identification and correct installation of this terminating element are important for maintaining stable industrial communication.