Operating Instructions | EN

EL1904
TwinSAFE Terminal with 4 digital fail-safe inputs

2023-09-22 | Version: 3.1.1

 Table of contents

Table of contents
1 Notes on the documentation.................................................................................................................... 5
1.1 Disclaimer.......................................................................................................................................... 5
1.1.1 Trademarks ........................................................................................................................ 5
1.1.2 Patents ............................................................................................................................... 5
1.1.3 Limitation of liability ............................................................................................................ 6
1.1.4 Copyright............................................................................................................................ 6
1.2 Documentation issue status .............................................................................................................. 7
1.3 Staff qualification ............................................................................................................................... 8
1.4 Safety and instruction........................................................................................................................ 9
1.4.1 Explanation of symbols ...................................................................................................... 9
1.5 Beckhoff Support and Service......................................................................................................... 10

2 For your safety ........................................................................................................................................ 11

2.1 Duty of care ..................................................................................................................................... 11
2.2 Safety image signs .......................................................................................................................... 12
2.3 General safety instructions.............................................................................................................. 13
2.3.1 Before operation............................................................................................................... 13
2.3.2 During operation............................................................................................................... 13
2.3.3 After operation.................................................................................................................. 13

3 System description ................................................................................................................................. 14

3.1 The Beckhoff Bus Terminal system ................................................................................................ 14
3.1.1 Bus Coupler ..................................................................................................................... 15
3.1.2 Bus Terminals .................................................................................................................. 16
3.1.3 E-bus................................................................................................................................ 16
3.1.4 Power contacts................................................................................................................. 16
3.2 TwinSAFE ....................................................................................................................................... 16
3.2.1 The I/O construction kit is extended safely ...................................................................... 16
3.2.2 Safety concept ................................................................................................................. 17
3.2.3 EL1904, EL2904 - Bus Terminals with 4 fail-safe inputs or outputs................................. 18
3.2.4 EL6900 - TwinSAFE logic terminal .................................................................................. 18
3.2.5 The fail-safe principle (Fail Stop) ..................................................................................... 18

4 Product description ................................................................................................................................ 19

4.1 EL1904 – TwinSAFE terminal with 4 digital fail-safe inputs ............................................................ 19
4.2 Intended use ................................................................................................................................... 20
4.3 Technical data ................................................................................................................................. 22
4.4 Safety parameters ........................................................................................................................... 23
4.5 Characteristic curve of the inputs .................................................................................................... 24
4.6 Dimensions ..................................................................................................................................... 25
4.7 Block diagram of the EL1904 .......................................................................................................... 25

5 Operation ................................................................................................................................................. 26
5.1 Environmental conditions ................................................................................................................ 26
5.2 Installation ....................................................................................................................................... 26
5.2.1 Safety instructions............................................................................................................ 26
5.2.2 Transport / storage........................................................................................................... 26

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Table of contents

5.2.3 Mechanical installation ..................................................................................................... 26

5.2.4 Electrical installation......................................................................................................... 30
5.2.5 TwinSAFE reaction times................................................................................................. 36
5.2.6 Tested EL1904 devices.................................................................................................... 37
5.3 Operation in potentially explosive atmospheres (ATEX) ................................................................. 38
5.3.1 Special conditions ............................................................................................................ 38
5.3.2 Identification ..................................................................................................................... 38
5.3.3 Date code and serial number ........................................................................................... 39
5.3.4 Further ATEX documentation........................................................................................... 39
5.4 Configuration of the terminal in TwinCAT ....................................................................................... 39
5.4.1 Inserting a Bus Coupler.................................................................................................... 39
5.4.2 Inserting a Bus Terminal .................................................................................................. 39
5.4.3 Inserting an EL1904 ......................................................................................................... 39
5.4.4 Address settings on TwinSAFE terminals with 65535 possible addresses...................... 41
5.4.5 Entering a TwinSAFE address and parameters in the System Manager......................... 42
5.5 Diagnostics...................................................................................................................................... 46
5.5.1 Diagnostic LEDs............................................................................................................... 46
5.5.2 Diagnostic objects ............................................................................................................ 47

6 Service life ............................................................................................................................................... 49

7 Maintenance and cleaning ..................................................................................................................... 50

8 Decommissioning ................................................................................................................................... 51
8.1 Disposal .......................................................................................................................................... 51
8.1.1 Returning to the vendor.................................................................................................... 51

9 Appendix .................................................................................................................................................. 52
9.1 Volatility ........................................................................................................................................... 52
9.2 Focus of certificates ........................................................................................................................ 53
9.3 Certificate ........................................................................................................................................ 54

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 Notes on the documentation

1 Notes on the documentation

1.1 Disclaimer
Beckhoff products are subject to continuous further development. We reserve the right to revise the
operating instructions at any time and without prior announcement. No claims for the modification of products
that have already been supplied may be made on the basis of the data, diagrams and descriptions in these
operating instructions.

In these operating instructions we define all permissible use cases whose properties and operating
conditions we can guarantee. The use cases we define are fully tested and certified. Use cases beyond this,
which are not described in these operating instructions, require the approval of Beckhoff Automation GmbH
& Co KG.

1.1.1 Trademarks
Beckhoff®, TwinCAT®, EtherCAT®, EtherCAT G®, EtherCAT G10®, EtherCAT P®, Safety over EtherCAT®,
TwinSAFE®, XFC®, XTS® and XPlanar® are registered and licensed trademarks of Beckhoff Automation
GmbH.
The use of other brand names or designations by third parties may lead to an infringement of the rights of
the owners of the corresponding designations.

1.1.2 Patents
The EtherCAT technology is protected by patent rights through the following registrations and patents with
corresponding applications and registrations in various other countries:
• EP1590927
• EP1789857
• EP1456722
• EP2137893
• DE102015105702

EtherCAT® is a registered trademark and patented technology,

licensed by Beckhoff Automation GmbH.

Safety over EtherCAT® is a registered trademark and patented

technology, licensed by Beckhoff Automation GmbH.

EL1904 Version: 3.1.1 5

Notes on the documentation

1.1.3 Limitation of liability

All components in this product as described in the operating instructions are delivered in a specific
configuration of hardware and software, depending on the application regulations. Modifications and
changes to the hardware and/or software configuration that go beyond the documented options are
prohibited and nullify the liability of Beckhoff Automation GmbH & Co. KG.

The following is excluded from the liability:

• Failure to observe these operating instructions
• Improper use
• Use of untrained personnel
• Use of unauthorized spare parts

1.1.4 Copyright
© Beckhoff Automation GmbH & Co. KG, Germany.
The distribution and reproduction of this document as well as the use and communication of its contents
without express authorization are prohibited.
Offenders will be held liable for the payment of damages. All rights reserved in the event of the grant of a
patent, utility model or design.

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 Notes on the documentation

1.2 Documentation issue status

Version Comment
3.1.1 • Certificate updated
3.1.0 • In chapter Technical data [} 22] corrosive gas test and footnote for corrosive environment
added
3.0.0 • Foreword changed in Notes on the documentation [} 5] and For your safety [} 11]
• In chapter Technical data [} 22] link to download page of certificates added
• Maintenance and cleaning [} 50] and Decommissioning [} 51] added
• Appendix adapted and extended
2.3.0 • Specification of overvoltage category added
• Protection class III (SELV/PELV) added
• Device type "Open equipment" added
• Link in chapter Actuality updated
2.2.0 • Notes on heights, operation modes, fuses and wiring added
• Notes on EN 81 added
• Notes added in section Intended Use
• Chapter Identification (ATEX) updated
2.1.1 • Technical data for permissible air pressure extended
2.1.0 • Chapter on Address settings on TwinSAFE terminals with 65535 possible addresses updated
• Links in the technical data corrected
2.0.0 • Migration and structural adaptation
• Reliability document updated
• Safety parameters updated
• Foreword revised
1.5.2 • Block diagram updated
• Numbering/table of contents changed (Chapter 4.1.5 to 4.1.7)
• Description of the test pulses added
• Description of the reaction times added
• Reliability document updated
1.5.1 • Certificate updated
1.5.0 • Company address changed
• Safety parameters extended
1.4.0 • Extended temperature range added
• Temperature measurement described
• Characteristic input curve added
• Description of date code extended
1.3.1 • Document origin added
1.3.0 • Clock output currents in the technical data added
• Block diagram for EL1904 added
1.2.1 • Reference to EN 60068-2-29 removed
1.2.0 • ATEX notes added
• Installation position / minimum distances extended
• Notes regarding overvoltage protection added
• Notes regarding cable length and clocked signals extended
• Diagnostics for CoE object 0x800E described
1.1.0 • Minor amendments for EtherCAT

EL1904 Version: 3.1.1 7

Notes on the documentation

Version Comment
• Copyright / disclaimer modified
• Support / service addresses updated
1.0.0 • First released version

Currentness

Please check whether you are using the current and valid version of this document. The current version can
be downloaded from the Beckhoff homepage at http://www.beckhoff.de/twinsafe. In case of doubt, please
contact Technical Support (see Beckhoff Support and Service [} 10]).

Origin of the document

The original documentation is written in German. All other languages are derived from the German original.

Product features

Only the product properties specified in the current operating instructions are valid. Further information given
on the product pages of the Beckhoff homepage, in emails or in other publications is not authoritative.

1.3 Staff qualification

These operating instructions are intended exclusively for trained specialists in control technology and
automation with the relevant knowledge.

The trained specialist personnel must ensure that the applications and use of the described product meet all
safety requirements. This includes all applicable and valid laws, regulations, provisions and standards.

Trained specialists

Trained specialists have extensive technical knowledge from studies, apprenticeships or technical training.
Understanding of control technology and automation is available. Trained specialists can:
• Independently identify, avoid and eliminate sources of hazard.
• Apply relevant standards and directives.
• Implement specifications from accident prevention regulations.
• Evaluate, prepare and set up the workplaces.
• Evaluate, optimize and execute work independently.

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 Notes on the documentation

1.4 Safety and instruction

Read the contents that refer to the activities you have to perform with the product. Always read the chapter
For your safety [} 11] in the operating instructions.

Observe the warnings in the chapters so that you can handle and work with the product as intended and
safely.

1.4.1 Explanation of symbols

Various symbols are used for a clear arrangement:
1. The numbering indicates an action that should be taken.
• The bullet point indicates an enumeration.
[…] The square brackets indicate cross-references to other text passages in the document.
[1] The number in square brackets indicates the numbering of a referenced document.

1.4.1.1 Signal words

The signal words used in the documentation are classified below.

Warning of personal injuries

DANGER
Hazard with high risk of death or serious injury.

WARNING
Hazard with medium risk of death or serious injury.

CAUTION
There is a low-risk hazard that could result in medium or minor injury.

Warning of damage to property or environment

NOTICE
Notes
The environment, equipment, or data may be damaged.

Information on handling the product

This information includes, for example:

Recommendations for action, assistance or further information on the product.

EL1904 Version: 3.1.1 9

Notes on the documentation

1.5 Beckhoff Support and Service

Support

Beckhoff Support offers technical advice on the use of individual Beckhoff products and system planning.
The employees support you in the programming and commissioning of sophisticated automation systems.
Hotline: +49 5246/963-157
E-mail: support@beckhoff.com
Web: www.beckhoff.com/support

Training

Training in Germany takes place in our training center at the Beckhoff headquarters in Verl, at subsidiaries
or, by arrangement, at the customer's premises.
Hotline: +49 5246/963-5000
E-mail: training@beckhoff.com
Web: www.beckhoff.com/training

Service

The Beckhoff Service Center supports you with after-sales services such as on-site service, repair service or
spare parts service.
Hotline: +49 5246/963-460
E-mail: service@beckhoff.com
Web: www.beckhoff.com/service

Download area

In the download area you can obtain product information, software updates, the TwinCAT automation
software, documentation and much more.
Web: www.beckhoff.com/download

Headquarters

Beckhoff Automation GmbH & Co. KG

Hülshorstweg 20
33415 Verl
Germany
Phone: +49 5246/963-0
E-mail: info@beckhoff.com
Web: www.beckhoff.com

For the addresses of our worldwide locations, please visit our website at Global Presence.

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 For your safety

2 For your safety

Read this chapter containing general safety information. In addition, always observe the safety instructions
and warnings in these operating instructions for your own safety, the safety of other persons and the safety
of the product.

When working with control and automation products, many dangers can result from careless or incorrect use.
Work particularly thoroughly, not under time pressure and responsibly towards other people.

2.1 Duty of care

Read entire documentation for TwinSAFE component
• TwinSAFE application manual
• EL6910 TwinSAFE logic terminal operating manual
• TwinSAFE Logic FB documentation manual

The operator must comply with all the requirements and notes specified in these operating instructions in
order to fulfill his duty of care. This includes in particular that you
• comply with the provisions defined in the chapter Limitation of liability [} 6].
• only operate the TwinSAFE component when it is in perfect working order.
• provide the operating instructions in a legible condition and complete at the place of use of the
TwinSAFE component.
• do not remove the safety markings attached to the TwinSAFE component and maintain their legibility.

No disposal in domestic waste

Products marked with a crossed-out waste bin must not be disposed of with domestic
waste. The device is considered waste electrical and electronic equipment when it is
disposed of. Observe the national regulations for the disposal of waste electrical and
electronic equipment.

EL1904 Version: 3.1.1 11

For your safety

2.2 Safety image signs

Beckhoff products feature safety pictograms, either on stickers or printed, which vary depending on the
product. They serve to protect people and to prevent damage to the products. Safety pictograms may not be
removed and must be legible for the user.

Read and observe the operating instructions

Commissioning is only permitted if the operating instructions have been read and
understood beforehand. This applies in particular to the safety instructions and the
warnings.

Electrostatic sensitive components

Work with and on the TwinSAFE component is only permitted at protected
workplaces.

12 Version: 3.1.1 EL1904

 For your safety

2.3 General safety instructions

2.3.1 Before operation

Use in machines according to the Machinery Directive

Only use the TwinSAFE component in machines that comply with the Machinery Directive. This is how you
ensure safe operation.

Ensure traceability

Ensure the traceability of the TwinSAFE component via the serial number.

Use SELV/PELV power supply

Use a SELV/PELV power supply unit with an output-side voltage limit of Umax = 36 VDC to supply the
TwinSAFE component with 24 VDC.

Failure to observe this will endanger the safety function of the product. Depending on the machine, death
and danger to life, serious physical injury and damage to the machine may result.

Use ferrules with plastic collars

If you use fine-wire cables for the signal connections, use ferrules with plastic collars. This leads to a higher
system availability when the test pulses for the corresponding channels are switched off.

Carry out commissioning test

Before commissioning, wiring faults to the sensors must be excluded. Before commissioning, carry out a
commissioning test. After a successful commissioning test, you can use the TwinSAFE component for the
intended safety-related task.

In case of wiring errors, the safety function of the product is at risk. Depending on the machine, death and
danger to life, serious bodily injury and damage to the machine may result.

2.3.2 During operation

Interference due to emitted interference

Do not operate the following devices in the vicinity of the TwinSAFE component: for example, radio
telephones, radios, transmitters or high-frequency systems.

TwinSAFE components comply with the requirements of the applicable electromagnetic compatibility
standards with regard to interference emission and immunity. If you exceed the limits for emitted interference
specified in the standards, the function of the TwinSAFE component may be impaired.

2.3.3 After operation

De-energize and switch off components before working on them

Check all safety-relevant equipment for functionality before working on the TwinSAFE component. Secure
the working environment. Secure the machine or plant against being inadvertently started up. Observe the
chapter Decommissioning [} 51].

EL1904 Version: 3.1.1 13

System description

3 System description

3.1 The Beckhoff Bus Terminal system

The Beckhoff Bus Terminal system is used for decentralized connection of sensors and actuators to a
control system. The Beckhoff Bus Terminal system components are mainly used in industrial automation and
building management applications. In its minimum configuration, a bus station consists of a Bus Coupler or a
Bus Terminal Controller and Bus Terminals connected to it. The Bus Coupler forms the communication
interface to the higher-level controller, and the terminals are the interface to sensors and actuators. The
whole bus station is clipped onto a 35 mm DIN mounting rail (EN 60715). The mechanical cross connection
of the bus station is established via a slot and key system at the Bus Coupler and the Bus Terminals.

The sensors and actuators are connected with the terminals via the screwless (spring-loaded) connection
system.

Fig. 1: Slot and key system and screwless (spring-loaded) connection system.

In order to accommodate the wide range of different communication standards encountered in industrial
automation, Beckhoff offers Bus Couplers for a number of common bus systems (e.g. EK1100 for
EtherCAT).

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 System description

3.1.1 Bus Coupler

Mechanical data Bus Coupler
Material polycarbonate, polyamide (PA6.6).
Dimensions (W x H x D) 44 mm x 100 mm x 68 mm
Mounting on 35 mm mounting rail (EN 60715) with locking
Attachable by double slot and key connection

Fig. 2: Bus Coupler (EtherCAT)

Connection technology Bus Coupler

Wiring spring-loaded system
Connection cross-section 0.08 mm² ... 2.5 mm², stranded wire, solid wire
Fieldbus connection depending on fieldbus
Power contacts 3 spring contacts
Current load 10 A
Rated voltage 24 VDC

EL1904 Version: 3.1.1 15

System description

3.1.2 Bus Terminals

Mechanical data Bus Terminal
Material polycarbonate, polyamide (PA6.6).
Dimensions (W x H x D) 12 mm x 100 mm x 68 mm or 24 mm x 100 mm x 68 mm
Mounting on 35 mm mounting rail (EN 60715) with locking
Attachable by double slot and key connection

Fig. 3: TwinSAFE Terminals (EtherCAT)

Connection technology Bus Terminal

Wiring spring-loaded system
Connection cross-section 0.08 mm² ... 2.5 mm², stranded wire, solid wire
Fieldbus connection E-bus
Power contacts up to 3 blade/spring contacts
Current load 10 A
Rated voltage depends on Bus Terminal type

3.1.3 E-bus
The E-bus is the data path within a terminal strip. The E-bus is led through from the Bus Coupler through all
the terminals via six contacts on the terminals' side walls.

3.1.4 Power contacts

The operating voltage is passed on to following terminals via three power contacts. Terminal strip can be
split into galvanically isolated groups by means of potential feed terminals as required. The power feed
terminals play no part in the control of the terminals, and can be inserted at any locations within the terminal
strip.

3.2 TwinSAFE

3.2.1 The I/O construction kit is extended safely

With the TwinSAFE Terminals, Beckhoff offers the option of simply expanding the proven Bus Terminal
system, and to transfer the complete cabling for the safety circuit into the already existing fieldbus cable.
Safe signals can be mixed with standard signals without restriction. This saves design effort, installation and
material. Maintenance is simplified significantly through faster diagnosis and simple replacement of only a
few components.

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 System description

The new ELx9xx series Bus Terminals only include three basic functionalities: digital inputs EL19xx, digital
outputs EL29xx and a logic unit EL6900. For a large number of applications, all sensors and actuators can
be wired on these Bus Terminals. The required logical link of the inputs and the outputs is handled by the
EL6900. For small to medium-sized configurations, the tasks of a fail-safe PLC can thus be handled within
the Bus Terminal system.

3.2.2 Safety concept

TwinSAFE: Safety and I/O technology in one system
• Extension of the familiar Beckhoff I/O system with TwinSAFE terminals
• Freely selectable mix of safe and standard signals
• Logical link of the I/Os in the EL6900 TwinSAFE logic terminal
• Safety-relevant networking of machines via bus systems

TwinSAFE protocol (FSoE)

• Transfer of safety-relevant data via any media (“genuine black channel”)
• TwinSAFE communication via fieldbus systems such as EtherCAT, Lightbus, PROFIBUS or Ethernet
• IEC 61508:2010 SIL 3 compliant

Configuring instead of wiring: the TwinSAFE configurator

• Configuration of the TwinSAFE system via the TwinCAT System Manager
• System Manager for editing and displaying all bus parameters
• Certified function blocks such as emergency stop, operation mode, etc.
• Simple handling
• Typical function blocks for machine safety
• any bus connection with the EL6900 TwinSAFE logic terminal

TwinSAFE logic Bus Terminal EL6900

• Link unit between TwinSAFE input and output terminals
• Configuration of a simple, flexible, cost-effective, decentralized safety controller
• No safety requirements for higher-level control system
• TwinSAFE enables networks with up to 65535 TwinSAFE devices.
• TwinSAFE Logic Terminal can establish up to 128 connections (TwinSAFE connections).
• Several TwinSAFE Logic Terminals are cascadable in a network
• Safety functions such as emergency stop, protective door, etc. are already included
• Suitable for applications up to SIL 3 according to IEC 61508:2010 and
DIN EN ISO 13849-1:2015 (Cat 4, PL e).

TwinSAFE digital input (EL1904) and output terminal (EL2904)

• All current safety sensors can be connected
• Operation with a TwinSAFE logic terminal
• EL1904 with 4 fail-safe inputs for sensors (24 VDC) with potential-free contacts
• EL2904 with four safe channels for actuators (24 VDC, 0.5 A per channel)
• Conforming to IEC 61508:2010 SIL 3 and EN ISO 13849-1:2015 (Cat 4, PL e) requirements.

EL1904 Version: 3.1.1 17

System description

3.2.3 EL1904, EL2904 - Bus Terminals with 4 fail-safe inputs or

outputs
The EL1904 and EL2904 Bus Terminals enable connection of common safety sensors and actuators. They
are operated with the EL6900 TwinSAFE logic terminal. The TwinSAFE logic terminal is the link unit between
the TwinSAFE input and output terminals. It enables the configuration of a simple, flexible and cost-effective
decentralized safety control system.

Therefore, there are no safety requirements for the higher-level controller! The typical safety functions
required for the automation of machines, such as emergency stop, protective door, two-hand etc., are
already permanently programmed in the EL6900. The user configures the EL6900 terminal according to the
safety requirements of his application.

3.2.4 EL6900 - TwinSAFE logic terminal

The TwinSAFE Logic Terminal is the link unit between the TwinSAFE input and output terminals. The
EL6900 meets the requirements of IEC 61508:2010 SIL 3 and EN ISO 13849-1:2015 (Cat 4, PL e).

3.2.5 The fail-safe principle (Fail Stop)

The basic rule for a safety system such as TwinSAFE is that failure of a part, a system component or the
overall system must never lead to a dangerous condition. The safe state is always the switched off and
wattless state.

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 Product description

4 Product description

4.1 EL1904 – TwinSAFE terminal with 4 digital fail-safe

inputs
The EL1904 is a digital input terminal for encoder with potential-free contacts for 24 V DC. The Bus Terminal
has 4 fail-safe inputs.

With two-channel connection, the EL1904 meets the requirements of IEC 61508:2010 SIL 3,
EN ISO 13849-1:2015 (Cat 4, PL e), NRTL, UL508, UL1998 and UL991.

The TwinSAFE terminal has the typical design of an EtherCAT terminal.

Fig. 4: EL1904 – TwinSAFE terminal with 4 digital fail-safe inputs

EL1904 Version: 3.1.1 19

Product description

4.2 Intended use

WARNING
Caution - Risk of injury!
TwinSAFE components shall only be used for the purposes described below!

The TwinSAFE terminals expand the application range of Beckhoff Bus Terminal system with functions that
enable them to be used for machine safety applications. The TwinSAFE terminals are designed for machine
safety functions and directly associated industrial automation tasks. They are therefore only approved for
applications with a defined fail-safe state. This safe state is the wattless state. Fail-safety according to the
relevant standards is required.

The TwinSAFE Terminals enable connection of:

• 24 VDC sensors (EL1904) such as
emergency off pushbutton switches, pull cord switches, position switches, two-hand switches, safety
mats, light curtains, light barriers, laser scanner, etc.
• 24 VDC actuators (EL2904) such as
contactors, protection door switches with tumbler, signal lamps, servo drives, etc.

Test pulses
When selecting actuators please ensure that the EL2904 test pulses do not lead to actuator
switching or diagnostic message from the EL2904.

The following TwinSAFE components have been developed for these tasks:
• The EL1904 is an EtherCAT Terminal with 4 digital fail-safe inputs.
• The EL2904 is an EtherCAT Terminal with 4 digital fail-safe outputs.
• The EL6900 is an EtherCAT Terminal with integrated TwinSAFE logic.

These TwinSAFE components are suitable for operation on the

• Beckhoff EKxxxx series Bus Couplers
• Beckhoff CXxxxx series Embedded PCs with E-bus connection

WARNING
Power supply from SELV/PELV power supply unit!
The TwinSAFE components must be supplied with 24 VDC by an SELV/PELV power supply unit with an
output voltage limit Umax of 36 VDC. Failure to observe this can result in a loss of safety.

CAUTION
Follow the machinery directive!
The TwinSAFE components shall only be used in machines as defined in the machinery directive.

CAUTION
Ensure traceability!
The buyer has to ensure the traceability of the device via the serial number.

WARNING
Commissioning test
Before the TwinSAFE terminal can be used for the safety task, the user must carry out a commissioning
test so that sensor and actuator wiring faults can be ruled out.

CAUTION
Use ferrules with plastic collars
When using fine-wire cables for signal connections, use ferrules with plastic collars. This leads to a higher
system availability when the test pulses for the corresponding channels are switched off.

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 Product description

CAUTION
Note on approval according to EN 81-20, EN 81-22 and EN 81-50
• The release does not apply to the EL1918-2200, EL2911-2200 and EP1957-2222 variants.
• The TwinSAFE components may only be used in machines that have been designed and installed in
accordance with the requirements of the EN 60204-1 standard.
• Provide a surge filter for the supply voltage of the TwinSAFE components against overvoltages
(reduction to overvoltage category II).
• EN 81 requires that in the case of devices with internal temperature monitoring, a stop must be reached
in the event of an overtemperature. In this case, passengers must be able to disembark (see EN 81-20
chapter 5.10.4.3, for example). To ensure this, application measures are necessary. The internal
terminal temperature of the TwinSAFE components can be read out by the user. A direct switch-off
occurs at the maximum permissible temperature of the respective TwinSAFE component (see chapter
Temperature measurement).
The user must select a temperature threshold below the maximum temperature such that a stop can be
reached in all cases before the maximum temperature is reached. Information on the optimum terminal
configuration can be found under Notes on the arrangement of TwinSAFE components and under
Example configuration for temperature measurement.
• For the use of the TwinSAFE components according to EN 81-22 and EN 81-50, the conditions
described in the manuals for achieving category 4 according to EN ISO 13849-1:2015 must be
observed.
• The use of TwinSAFE components is limited to indoor applications.
• Basic protection against direct contact must be provided, either by fulfilling protection class IP2X or by
installing the TwinSAFE components in a control cabinet which corresponds at least to protection class
IP54 according to EN 60529.
• The ambient conditions regarding temperature, humidity, heat dissipation, EMC and vibrations, as
specified in the operating instructions under technical data, must be observed.
• The operating conditions in potentially explosive atmospheres (ATEX) are specified in the operating
instructions.
• The safe state (triggering) of the application must be the de-energized state. The safe state of the
TwinSAFE components is always the de-energized, switched-off state, and this cannot be changed.
• The service life specified in the operating instructions must be observed.
• If the TwinSAFE component is operated outside the permissible temperature range, it changes to
"Global Shutdown" state.
• The TwinSAFE components must be installed in a control cabinet with protection class IP54 according to
EN 60529, so that the requirement for degree of pollution 3 according to EN 60664-1 can be reduced to
level 2.
• The TwinSAFE components must be supplied by a SELV/PELV power supply unit with a maximum
voltage of Umax ≤ 36 VDC.

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Product description

4.3 Technical data

The current certificates of all TwinSAFE products with the underlying standards and directives can be found
at https://www.beckhoff.com/en-en/support/download-finder/certificates-approvals/.
Product designation EL1904
Number of inputs 4
Status display 4 (one green LED per input)
Response time (read input/write to E-bus) typically: 4 ms,
maximum: see fault reaction time
Fault reaction time ≤ watchdog time
Cable length between sensor and terminal unshielded max. 100 m (with 0.75 or 1 mm²)
shielded max. 100 m (with 0.75 or 1 mm²)
Output current of the clock outputs typically 10 mA, max. 15 mA
Input process image 6 bytes
Output process image 6 bytes
EL1904 supply voltage (PELV) 24 VDC (–15% / +20%)
(A 10 A fuse should be provided for the potential group)
Protection class III
(by using a SELV/PELV power supply unit)
Overvoltage category II
Signal voltage "0" inputs -3 V ... 5 V (EN 61131-2, type 3)
(see chapter Characteristic curve of the inputs [} 24])
Signal voltage "1" inputs 11 V ... 30 V (EN 61131-2, type 3)
(see chapter Characteristic curve of the inputs [} 24])
Current consumption of the module electronics at 24 V 4 channels occupied: typically 12 mA
(without current consumption of sensors) 0 channels occupied: typically 1.4 mA
Current consumption via E-bus 4 channels occupied: approx. 200 mA
Power loss of the terminal typically 1 W
Electrical isolation (between the channels) no
Electrical isolation (between the channels and the E-bus) yes
Insulation voltage (between the channels and the E-bus, Insulation tested with 500 VDC
under common operating conditions)
Dimensions (W x H x D) 12 mm x 100 mm x 68 mm
Weight approx. 50 g
Permissible ambient temperature (operation) 0 °C ... +55 °C
up to SW 05 (see chapter Example configuration for temperature measurement
[} 28])
Permissible ambient temperature (operation) -25 °C ... +55 °C
from SW 06 (CW 02/2014) (see chapter Example configuration for temperature measurement
[} 28])
Permissible ambient temperature (transport/storage) -40 °C ... +70 °C
Permissible air humidity 5% ... 95%, non-condensing
Permissible air pressure (operation/storage/transport) 750 hPa to 1100 hPa
(this is equivalent to an altitude of approx. -690 m to 2450 m above sea
level assuming an international standard atmosphere)
Climate category according to EN 60721-3-3 3K3
(the deviation from 3K3 is possible only with optimal environmental
conditions and also applies only to the technical data which are
specified differently in this documentation)
Permissible degree of pollution 2
according to EN 60664-1 (see chapter Maintenance)
Inadmissible operating conditions TwinSAFE Terminals must not be used under the following operating
conditions:
• under the influence of ionizing radiation (exceeding the natural
background radiation)
• in corrosive environments1
• in an environment that leads to unacceptable soiling of the bus
terminal
EMC immunity / emission conforms to EN 61000-6-2 / EN 61000-6-4
Vibration / shock resistance conforms to EN 60068-2-6 / EN 60068-2-27
Shocks 15 g with pulse duration 11 ms in all three axes
Corrosive gas test According to DIN EN 60068-2-60:2016-06, method 4 with increased
concentrations according to ANSI/ISA 71.04:2013 Level GX Group A

22 Version: 3.1.1 EL1904

 Product description

Product designation EL1904

• Test duration: 21 days
• Hydrogen sulfide: (50 ± 5) ppb
• Nitrogen dioxide: (1250 ± 20) ppb
• Chlorine: (10 ± 5) ppb
• Sulfur dioxide: (300 ± 20) ppb
Protection rating IP20
Device type according to EN 61010-2-201 Open equipment
Permitted operating environment In the control cabinet or terminal box, with minimum protection rating
IP54 according to IEC 60529
Permissible installation position see chapter Installation position and minimum distances [} 27]
Approvals CE, cULus, ATEX, TÜV SÜD

1
A corrosive environment exists when corrosion damage becomes apparent.

Derating table for altitudes above 2000 m

The derating table (table 8) from the IEC 61131-2:2017 standard can be referred to for the use of the
TwinSAFE components above the specified maximum altitude.
Altitude in m Derating factor for the temperature1
0 to 20002 1.0
3000 0.9
4000 0.8
5000 0.7
Note: Linear interpolation is permissible between the altitudes
1)
Ambient temperature of the device at an altitude of 2000 m
2)
The air pressure and air density increase as the altitude decreases. Therefore the derating factor for 0 to
2000 m (1.0) is used for altitudes below sea level.

Calculation example

In the following example the calculation is performed for a TwinSAFE component at an operating altitude of
4000 m.

Permissible ambient temperature up to 2000 m above sea level = 55 °C

Permissible ambient temperature up to 4000 m above sea level = 55 °C * 0.8 = 44 °C

CAUTION
Compliance with the temperature limits
The TwinSAFE component has a maximum internal temperature at which a switch-off takes place. This is
designed for the maximum permissible ambient temperature. If the derating factor for the temperature for
higher altitudes is used, the user is solely responsible for ensuring that the calculated maximum ambient
temperature is complied with.

4.4 Safety parameters

Characteristic numbers EL1904
Lifetime [a] 20
Prooftest Interval [a] not required 1
PFHD 1.11E-09
%SIL3 1.11%
PFD 8.29E-05
%SIL3 8.29 %
MTTFd high

EL1904 Version: 3.1.1 23

Product description

Characteristic numbers EL1904

DC high
Performance level PL e
Category 4
HFT 1
Element classification 2 Type B

1. Special proof tests are not required during the entire service life of the EL1904 EtherCAT terminal.
2. Classification according to IEC 61508-2:2010 (chapter 7.4.4.1.2 and 7.4.4.1.3)

The EL1904 EtherCAT Terminal can be used for safety-related applications within the meaning of
IEC 61508:2010 up to SIL3 and EN ISO 13849-1:2015 up to PL e (Cat4).

For the calculation or estimation of the MTTFd value from the PFHD value, further information can be found in
the TwinSAFE Application Guide or in ISO 13849-1:2015 Table K.1.

4.5 Characteristic curve of the inputs

The characteristic curve of the inputs is similar to type 3 according to EN 61131-2.

Fig. 5: Characteristic curve of the inputs

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 Product description

4.6 Dimensions

Fig. 6: Dimensions of the EL1904

Width: 12 mm (side-by-side installation)

Height: 100 mm
Depth: 68 mm

4.7 Block diagram of the EL1904

Fig. 7: Block diagram of the EL1904

The block diagram shows the basic configuration of a channel in the EL1904. The part with a red border is
present four times in the terminal.

EL1904 Version: 3.1.1 25

Operation

5 Operation

5.1 Environmental conditions

Please ensure that the TwinSAFE components are only transported, stored and operated under the specified
conditions (see technical data)!

WARNING
Risk of injury!
The TwinSAFE components must not be used under the following operating conditions.
• under the influence of ionizing radiation (that exceeds the level of the natural environmental radiation)
• in corrosive environments
• in an environment that leads to unacceptable soiling of the TwinSAFE component

NOTICE
Electromagnetic compatibility
The TwinSAFE components comply with the current standards on electromagnetic compatibility with regard
to spurious radiation and immunity to interference in particular.
However, in cases where devices such as mobile phones, radio equipment, transmitters or high-frequency
systems that exceed the interference emissions limits specified in the standards are operated near
TwinSAFE components, the function of the TwinSAFE components may be impaired.

5.2 Installation

5.2.1 Safety instructions

Before installing and commissioning the TwinSAFE components please read the safety instructions in the
foreword of this documentation.

5.2.2 Transport / storage

Use the original packaging in which the components were delivered for transporting and storing the
TwinSAFE components.

CAUTION
Note the specified environmental conditions
Please ensure that the digital TwinSAFE components are only transported and stored under the specified
environmental conditions (see technical data).

5.2.3 Mechanical installation

WARNING
Risk of injury!
Bring the bus system into a safe, de-energized state before starting installation, disassembly or wiring of
the devices!

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 Operation

5.2.3.1 Control cabinet / terminal box

The TwinSAFE terminals must be installed in a control cabinet or terminal box with IP54 protection class
according to IEC 60529 as a minimum.

5.2.3.2 Installation position and minimum distances

For the prescribed installation position the mounting rail is installed horizontally and the mating surfaces of
the EL/KL terminals point toward the front (see illustration below). The terminals are ventilated from below,
which enables optimum cooling of the electronics through convection. The direction indication “down”
corresponds to the direction of positive acceleration due to gravity.

Fig. 8: Installation position and minimum distances

In order to ensure optimum convection cooling, the distances to neighboring devices and to control cabinet
walls must not be smaller than those shown in the diagram.

EL1904 Version: 3.1.1 27

Operation

5.2.3.3 Example configuration for temperature measurement

Fig. 9: Example configuration for temperature measurement

The example configuration for the temperature measurement consists of an EK1100 EtherCAT coupler with
connected terminals that match the typical distribution of digital and analog signal types at a machine. On the
EL6900 a safety project is active, which reads safe inputs and enables all 4 safe outputs during the
measurement.

External heat sources / radiant heat / impaired convection

The maximum permissible ambient temperature of 55°C was checked with the above example
configuration. Impaired convection, an unfavorable location near heat sources or an unfavorable
configuration of the EtherCAT Terminals may result in overheating of the terminals.
The key parameter is always the maximum permitted internally measured temperature of 95°C,
above which the TwinSAFE terminals switch to safe state and report an error. The internal
temperature can be read from the TwinSAFE components via CoE (see chapter Diagnose).

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5.2.3.4 Installation on mounting rails

WARNING
Risk of electric shock and damage of device!
Bring the bus terminal system into a safe, powered down state before starting installation, disassembly or
wiring of the Bus Terminals!

Mounting

Fig. 10: Installation on the mounting rail

The Bus Couplers and Bus Terminals are attached to commercially available 35 mm mounting rails (DIN rail
according to EN 60715) by applying slight pressure:

1. First attach the Fieldbus Coupler to the mounting rail.

2. The Bus Terminals are now attached on the right-hand side of the Fieldbus Coupler. Join the
components with slot and key and push the terminals against the mounting rail, until the lock clicks
onto the mounting rail.
If the terminals are clipped onto the mounting rail first and then pushed together without slot and key,
the connection will not be operational! When correctly assembled, no significant gap should be visible
between the housings.

Fastening of mounting rails

The locking mechanism of the terminals and couplers protrudes into the profile of the mounting rail.
When installing the components, make sure that the locking mechanism doesn't come into conflict
with the fixing bolts of the mounting rail. For fastening mounting rails with a height of 7.5 mm under
the terminals and couplers, use flat fastening components such as countersunk head screws or
blind rivets.

EL1904 Version: 3.1.1 29

Operation

Disassembly

Fig. 11: Removal from mounting rail

Each terminal is secured by a lock on the mounting rail, which must be released for disassembly:

1. Pull down the terminal at its orange-colored straps from the mounting rail by approx. 1 cm. The rail
locking of this terminal is automatically released, and you can now pull the terminal out of the Bus
Terminal block with little effort.
2. To do this, grasp the unlocked terminal simultaneously at the top and bottom of the housing surfaces
with your thumb and index finger and pull it out of the Bus Terminal block.

5.2.4 Electrical installation

5.2.4.1 Connections within a Bus Terminal block

The electric connections between the Bus Coupler and the Bus Terminals are automatically realized by
joining the components:

Spring contacts (E-bus)

The six spring contacts of the E-bus deal with the transfer of the data and the supply of the Bus Terminal
electronics.

NOTICE
Observe the E-bus current
Observe the maximum current that your Bus Coupler can supply to the E-bus! Use the EL9410 Power
Supply Terminal if the current consumption of your terminals exceeds the maximum current that your Bus
Coupler can feed to the E-bus supply.

Power contacts

The power contacts deal with the supply for the field electronics and thus represent a supply rail within the
Bus Terminal block. The power contacts are supplied via terminals on the Bus Coupler.

Note the connection of the power contacts

During the design of a Bus Terminal block, the pin assignment of the individual Bus Terminals must
be taken account of, since some types (e.g. analog Bus Terminals or digital 4-channel Bus
Terminals) do not or not fully loop through the power contacts.
Potential supply terminals (EL91xx, EL92xx) interrupt the power contacts and thus represent the
start of a new supply rail.

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 Operation

PE power contact

The power contact labelled PE can be used as a protective earth. For safety reasons this contact mates first
when plugging together, and can ground short-circuit currents of up to 125 A.

Fig. 12: PE power contact

CAUTION
Insulation tests
Note that, for reasons of electromagnetic compatibility, the PE contacts are capacitatively coupled to the
mounting rail. This may lead to incorrect results during insulation testing or to damage on the terminal (e.g.
disruptive discharge to the PE line during insulation testing of a consumer with a rated voltage of 230 V).
For insulation testing, disconnect the PE supply line at the Bus Coupler or the Potential Supply Terminal! In
order to decouple further feed points for testing, these Power Feed Terminals can be released and pulled at
least 10 mm from the group of terminals.

DANGER
Serious risk of injury!
The PE power contact must not be used for other potentials!

5.2.4.2 Overvoltage protection

If protection against overvoltage is necessary in your plant, provide a surge filter for the voltage supply to the
Bus Terminal blocks and the TwinSAFE terminals.

EL1904 Version: 3.1.1 31

Operation

5.2.4.3 Wiring

Fig. 13: Connection of a cable to a terminal point

Up to eight terminal points enable the connection of solid or finely stranded cables to the Bus Terminal. The
terminal points are implemented in spring force technology. Connect the cables as follows:

1. Open a terminal point by pushing a screwdriver straight against the stop into the square opening
above the terminal point. Do not turn the screwdriver or move it alternately (don't toggle).
2. The wire can now be inserted into the round terminal opening without any force.
3. The terminal closes automatically when the pressure is released, holding the wire safely and
permanently.

See the following table for the suitable wire size width.
Wire size width (single core wires) 0.08 ... 2.5 mm2
Wire size width (fine-wire conductors) 0.08 ... 2.5 mm2
Wire size width (conductors with a wire end sleeve) 0.14 ... 1.5 mm2
Wire stripping length 8 ... 9 mm

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5.2.4.4 EL1904 pin assignment

Fig. 14: EL1904 pin assignment

Terminal point Input Signal

1 1 Input 1+
2 Input 1-
3 3 Input 3+
4 Input 3-
5 2 Input 2+
6 Input 2-
7 4 Input 4+
8 Input 4-

Configurable inputs
The inputs 1 to 4 can be occupied as you want with normally closed contacts or normally open
contacts. The corresponding analysis is carried out in the safety PLC.

EL1904 Version: 3.1.1 33

Operation

5.2.4.5 Signal cables

Permitted cable length

Fig. 15: Permitted cable length

When connecting a single switching contact via its own continuous cabling (or via a non-metallic sheathed
cable), the maximum permitted cable length is 100 m.

The use of contact points, connectors or additional switching contacts in the cabling reduces the maximum
propagation.

Cable routing

Fig. 16: Cable routing

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 Operation

NOTICE
Route the signal cable separately
The signal cable must be routed separately from potential sources of interference, such as motor supply
cables, 230 VAC power cables etc.!
Interference caused by cables routed in parallel can influence the signal form of the test pulses and thus
cause diagnostic messages (e.g. sensor errors or OpenLoad errors).
D: Distance between the cable ducts should be as large as possible
blue arrows: signal line
red arrows: potential source of interference

The common routing of signals together with other clocked signals in a common cable also reduces the
maximum propagation, since crosstalk of the signals can occur over long cable lengths and cause diagnostic
messages.

The test pulses can be switched off (sensor test parameter) if the connection of a common cable is
unavoidable. However, this then leads to a reduction in the degree of diagnostic cover when calculating the
performance level.

Test pulses

The typical length of a test pulse (switching from 24 V to 0 V and back to 24 V) is 350 µs and takes place
approx. 250 times per second.

The test pulses at the outputs Input 1+ to Input 4+ are generated separately for each channel in order to be
able to detect cross-circuits between the individual channels of a terminal and also between channels of
different terminals. In order to generate test pulses as shown in the diagram, the sensor test active safety
parameter must be set to true for the respective channels. The test cycle for all four channels is typically 4
ms. The times between the test pulses of different channels vary, thus allowing better diagnostic detection.

Fig. 17: Typical course of test pulses of the inputs

If self-testing sensors are to be used on the safe inputs, please refer to chapter Configuration for light
barriers, light grids, light curtains etc [} 44].

EL1904 Version: 3.1.1 35

Operation

5.2.5 TwinSAFE reaction times

The TwinSAFE terminals form a modular safety system that exchanges safety-oriented data via the Safety-
over-EtherCAT protocol. This chapter is intended to help you determine the system's reaction time from the
change of signal at the sensor to the reaction at the actuator.

Typical response time

The typical response time is the time required for transferring a piece of information from the sensor to the
actuator, when the whole system operates normally, without error.

Fig. 18: Typical response time

Definition Description
RTSensor Response time of the sensor, until the signal is made available at the interface. Typically
provided by the sensor manufacturer.
RTInput Response time of the safe input, e.g. EL1904 or EP1908. This time can be found in the
technical data. In the case of the EL1904 it is 4 ms.
RTComm Response time of the communication. This is typically 3 times the EtherCAT cycle time, since a
new Safety-over-EtherCAT telegram has to be generated before new data can be sent. These
times depend directly on the higher-level standard controller (cycle time of the PLC/NC).
RTLogic Response time of the logic terminal. This is the cycle time of the logic terminal and typically
ranges from 500 µs to 10 ms for the EL6900, depending on the size of the safety project. The
actual cycle time can be read from the terminal.
RTOutput Response time of the output terminal. This is typically between 2 and 3 ms.
RTActuator Response time of the actuator. This information is typically provided by the actuator
manufacturer
WDComm Watchdog time of the communication

The typical response time is based on the following formula:

ReactionTimetyp = RTSensor + RTInput + 3* RTComm + RTLogic + 3* RTComm + RTOutput + RTActuator

with
ReactionTimetyp = 5ms + 4ms + 3*1ms + 10ms + 3*1ms + 3ms + 20ms = 48ms

Worst case response time

The worst-case response time is the maximum time required for switching off the actuator in the event of an
error.

36 Version: 3.1.1 EL1904

 Operation

Fig. 19: Worst case response time

It is assumed that a signal change takes place at the sensor, and that this is passed to the input. A
communication error occurs just at the moment when the signal is to be passed to the communication
interface. This is detected by the logic once the watchdog time of the communication link has elapsed. This
information should then be passed on to the output, resulting in a further communication error. This fault is
detected at the output once the watchdog time has elapsed, resulting in shutdown.

This results in the following formula for the worst-case response time:
ReactionTimemax = WDComm + WDComm + RTActuator

with
ReactionTimemax = 2 *15ms + 20ms = 50ms

5.2.6 Tested EL1904 devices

The following list contains devices that were tested together with the EL1904 TwinSAFE terminal. The
results only apply for the current device hardware version at the time of testing. The tests were carried out in
a laboratory environment. Modifications of these products cannot be considered here. If you are unsure
please test the hardware together with the TwinSAFE terminal.

Manufacturer Type Comment

SICK C4000 Safety light curtain
SICK S3000 Safety laser scanner
Wenglor SG2-14ISO45C1 Safety light grids
Leuze lumiflex ROBUST 42/43/44 Safety light barriers
Schmersal BNS250-11ZG Safety switch
ifm GM701S Inductive safety sensor
Keyence SL-V (with PNP cable set) Safety light curtain

The tests were carried out as function tests only. The information provided in the respective manufacturer
documentation remains valid.

EL1904 Version: 3.1.1 37

Operation

5.3 Operation in potentially explosive atmospheres (ATEX)

5.3.1 Special conditions

WARNING
Observe the special conditions for the intended use of Beckhoff fieldbus components in
potentially explosive areas (directive 94/9/EU)!
The certified components are to be installed in a suitable housing that guarantees a protection class of at
least IP54 in accordance with EN 60529! The environmental conditions during use are thereby to be taken
into account!
If the temperatures during rated operation are higher than 70 °C at the feed-in points of cables, lines or
pipes, or higher than 80°C at the wire branching points, then cables must be selected whose temperature
data correspond to the actual measured temperature values!
Observe the permissible ambient temperature range of 0 to 55 °C when using Beckhoff fieldbus
components in potentially explosive atmospheres!
Measures must be taken to protect against the rated operating voltage being exceeded by more than 40%
due to short-term interference voltages!
The individual terminals may only be unplugged or removed from the Bus Terminal system if the supply
voltage has been switched off or if a non-explosive atmosphere is ensured!
The connections of the certified components may only be connected or disconnected if the supply voltage
has been switched off or if a non-explosive atmosphere is ensured!
The fuses of the EL92xx power feed terminals may only be exchanged if the supply voltage has been
switched off or if a non-explosive atmosphere is ensured!
Address selectors and ID switches may only be adjusted if the supply voltage has been switched off or if a
non-explosive atmosphere is ensured!

The fundamental health and safety requirements are fulfilled by compliance with the following standards:
• EN 60079-0: 2006
• EN 60079-15: 2005

5.3.2 Identification
Beckhoff fieldbus components that are certified for use in potentially explosive atmospheres bear one of the
following markings:

II 3 G Ex nA IIC T4 Gc KEMA 10ATEX0075 X

Ta: 0 … 55 °C

or

II 3 G Ex nA nC IIC T4 Gc KEMA 10ATEX0075 X

Ta: 0 … 55 °C

38 Version: 3.1.1 EL1904

 Operation

5.3.3 Date code and serial number

The TwinSAFE terminals bear a date code, which is composed as follows:

Date code: CW YY SW HW
Legend: Sample: Date code 29 10 02 01
CW: Calendar week of manufacture Calendar week: 29
YY: Year of manufacture Year: 2010
SW: Software version Software version: 02
HW: Hardware version Hardware version: 01

In addition the TwinSAFE terminals bear a unique serial number.

5.3.4 Further ATEX documentation

Please also refer to the further documentation
Notes regarding application of the Bus Terminal system in areas potentially explosive atmosphere
are available in the Download section of the Beckhoff website at http://www.beckhoff.de.

5.4 Configuration of the terminal in TwinCAT

Identical configuration
The configuration of the terminal in TwinCAT is identical for the variant.

CAUTION
Do not change CoE objects!
Do not change any of the CoE objects in the TwinSAFE terminals. Any modifications (e.g. via TwinCAT) of
the CoE objects will permanently set the terminals to the Fail-Stop state or lead to unexpected behavior of
the terminals!

5.4.1 Inserting a Bus Coupler

See TwinCAT automation software documentation.

5.4.2 Inserting a Bus Terminal

See TwinCAT automation software documentation.

5.4.3 Inserting an EL1904

An EL1904 is inserted in the same way as any other Beckhoff Bus Terminal. In the list open Safety
Terminals (ELx9xx) and select the EL1904.

EL1904 Version: 3.1.1 39

Operation

Fig. 20: Inserting an EL1904

40 Version: 3.1.1 EL1904

 Operation

5.4.4 Address settings on TwinSAFE terminals with 65535 possible

addresses

Fig. 21: Address settings on TwinSAFE terminals with 65535 possible addresses

Set the TwinSAFE address for the terminal using the two dip switches (with 8 setting options) on the left-
hand side of the EL1904 TwinSAFE terminal. TwinSAFE addresses between 1 and 65535 are available.

DIP switches Ad-

dress
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
ON OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF 1
OFF ON OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF 2
ON ON OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF 3
OFF OFF ON OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF 4
ON OFF ON OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF 5
OFF ON ON OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF 6
ON ON ON OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF 7
OFF OFF OFF ON OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF 8
… … … … … … … … … … … … … … … … …
ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON 65535

WARNING
TwinSAFE address
Each TwinSAFE address may only be used once within a network!
The address 0 is not a valid TwinSAFE address!

EL1904 Version: 3.1.1 41

Operation

5.4.5 Entering a TwinSAFE address and parameters in the System

Manager
The TwinSAFE address set at the DIP switch must also be entered in tab FSoE (under FSoE address) under
the EL1904.

Fig. 22: Entering the FSoE address

The EL1904 parameters are set under the respective TwinSAFE connection in the Connection and
Parameter tabs.

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 Operation

Fig. 23: Setting the connection of the TwinSAFE connection

Fig. 24: Setting the parameters of the TwinSAFE connection

Parameter overview

PrmName Meaning Values

FSoE_Address DIP switch address 1 to 65535
Operating Mode Digital / standstill monitoring 1 and 2 Digital / standstill 1 and 2
(Standstill monitoring is not supported)
Sensor test The clock signal for connection Input1+ true / false
channel 1 active is checked at connection Input1-.
Sensor test The clock signal for connection Input2+ true / false
channel 2 active is checked at connection Input2-.

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Operation

PrmName Meaning Values

Sensor test The clock signal for connection Input3+ true / false
channel 3 active is checked at connection Input3-.
Sensor test The clock signal for connection Input4+ true / false
channel 4 active is checked at connection Input4-.
Logic channel 1 Logic of channels 1 and 2 • single logic
and 2 • asynchronous repetition OSSD (sensor
test must be switched off)
• any pulse repetition OSSD (sensor test
must be switched off)
• short cut is no module fault
Logic channel 3 Logic of channels 3 and 4 • single logic
and 4 • asynchronous repetition OSSD (sensor
test must be switched off)
• any pulse repetition OSSD (sensor test
must be switched off)
• short cut is no module fault
Store Code This parameter is required for the 0x0000
TwinSAFE Restore Mode
Project CRC This parameter is required for the 0x0000
TwinSAFE Restore Mode

5.4.5.1 EL1904 configuration for light barriers, light grids, light curtains etc.
The EL1904 also supports direct connection of contact-free protective devices with two self-testing outputs
such as light barriers, light grids, light curtains, laser scanners, etc.

CAUTION
Sensors with self-testing outputs!
Only sensors with self-testing outputs and a maximum sensor self-test duration of 350 µs may be
connected to the EL1904 (see illustration below).

Fig. 25: Maximum permissible sensor self-test duration of 350 µs

Parameter

To connect these sensors please set the following parameters for the EL1904 in the TwinCAT System
Manager:

44 Version: 3.1.1 EL1904

 Operation

Connect the two sensor signals either to channels 1 and 2 or channels 3 and 4 and activate asynchronous
repetition OSSD or any pulse repetition for the two inputs used under parameter Logic for channel x and y.
The difference between these settings is that with any pulse repetition simultaneous tests of the OSSD
signals up to 350 µs are allowed.

For the two inputs used set the sensor test for the EL1904 to false.

5.4.5.2 Configuration of the EL1904 for safety switching mats

The EL1904 also supports direct connection of safety switching mats.

Parameter

To connect these switching mats please set the following parameters for the EL1904 in the TwinCAT System
Manager:

Connect the two sensor signals either to channels 1 and 2 or channels 3 and 4 and activate short cut
channel x/y is no module fault for the two inputs used under parameter Logic for channel x and y.

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Operation

5.5 Diagnostics

5.5.1 Diagnostic LEDs

The LEDs Diag 1 to Diag 4 display diagnostic information for the EL1904.

5.5.1.1 Diag 1 (green)

The Diag 1 LED indicates the state of the TwinSAFE interface.

Flashing Code Meaning

LED illuminated continuously normal operation:
TwinSAFE communication OK
rapid flickering, alternating with 1 flash pulse Error in S parameter (TwinSAFE parameter)
rapid flickering, alternating with 2 flash pulses Error in I parameter (Individual parameter)
rapid flickering, alternating with 3 flash pulses Waiting for S and I parameter
rapid flickering, alternating with 4 flash pulses S- and I-parameter correct:
waiting for first host message
rapid flickering, alternating with 5 flash pulses Watchdog error
rapid flickering, alternating with 6 flash pulses CRC error
rapid flickering, alternating with 7 flash pulses Sequence number error
rapid flickering, alternating with 8 flash pulses Communication error in the TwinSAFE protocol

5.5.1.2 Diag 2 (red)

The Diag 2 LED illuminates red if the terminal detects an external supply or cross-circuit. The LED
extinguishes once the error is rectified.

5.5.1.3 Diag 3 (red) and Diag 4 (red)

If the Diag 3 LED is lit, the Diag 4 LED indicates internal terminal errors.

Flashing Codes

In the case of such an error, the Diag 4 LED on the EL1904 displays flashing codes that describe the error in
more detail.

A flashing code consists of four sequences, which are interrupted in each case by a short break. After the
four sequences there is a long break, following which the flashing code is displayed again.

Count the individual sequences of the flashing code.

46 Version: 3.1.1 EL1904

 Operation

The errors indicated by the following flashing codes are reversible. After successful troubleshooting the
terminal can be restarted.

Diag 3 LED Diag 4 LED

Flashing Meaning Remedy
Code
lit 6-1-1-1 max. internal temperature Ensure that the permissible ambient
exceeded temperature is adhered to.
7-1-1-1 internal temperature below min.
value
2-1-2-1 max. supply voltage µC1 Check the supply voltage.
exceeded
3-1-2-1 max. supply voltage µC2
exceeded
4-1-2-1 voltage fell below min. supply
voltage µC1
5-1-2-1 voltage fell below min. supply
voltage µC2
8-1-1-1 Temperature difference between Check the installation position and the
the measuring points exceeded ambient temperature.

If another flashing code is displayed, this means that there is an internal terminal error that has stopped the
terminal. In this case the terminal must be checked by Beckhoff Automation GmbH & Co. KG.

Note the flashing codes and return the terminal

Note the flashing code displayed and include this information with the terminal when you return it.

5.5.2 Diagnostic objects

CAUTION
Do not change CoE objects!
Do not make any modifications to the CoE objects in the TwinSAFE components! Any modifications (e.g.
using TwinCAT) of the CoE objects will permanently set the TwinSAFE components to the Fail-Stop state.

Index FA80hex: Internal temperature values

The CoE object FA80hex indicates the current internal temperature values of the EL1904.

Index Name Meaning Flags Default

FA80:01 Temperature 1 Temperature measurement 1 RO 0bin
FA80:02 Temperature 2 Temperature measurement 2 RO 0bin

Index 800Ehex: diagnostic information

The CoE object 800Ehex displays further diagnostic information.

Index Name Meaning Flags Default

800E:0 Diag The following sub-indices contain detailed diagnostic RO
information.
800E:0A Sensor test error Bit Error during the sensor test RO
0 1bin Error at input 1 0bin
1 1bin Error at input 2 0bin
2 1bin Error at input 3 0bin
3 1bin Error at input 4 0bin

EL1904 Version: 3.1.1 47

Operation

Index Name Meaning Flags Default

800E:0B Error during two- Bit Error during the contiguous evaluation of two channels, RO
channel i.e. the two channels contradict each other.
evaluation 0 1bin Error in the first input pair 0bin
1 1bin Error in the second input pair 0bin
800E:0C Error in the safety Bits Error in the input pair RO
mat 1, 0 11bin Error in the first input pair 00bin
operation mode:
3, 2 11bin Error in the second input pair 00bin
input pair disagree
800E:0D Error in the safety Bit Error in the test pulses in the safety mat operating RO
mat mode; i.e. the terminal has detected an external
operation mode: supply.
external supply 0 1bin Error at input 1 0bin
1 1bin Error at input 2 0bin
2 1bin Error at input 3 0bin
3 1bin Error at input 4 0bin

Differing diagnostic messages possible

Due to the variable order or execution of the test series, diagnostic messages differing from those
given in the table above are possible.

48 Version: 3.1.1 EL1904

 Service life

6 Service life
The TwinSAFE terminals are designed for a service life of 20 years.

Due to the high diagnostic coverage within the lifecycle no special proof tests are required.

The TwinSAFE terminals bear a date code, which is composed as follows:

Date code: CW YY SW HW
Legend: Sample: Date Code 17 11 05 00
CW: Calendar week of manufacture Calendar week: 17
YY: Year of manufacture Year: 2011
SW: Software version Software version: 05
HW: Hardware version Hardware version: 00

In addition the TwinSAFE terminals bear a unique serial number.

00000000
17110500

Fig. 26: Unique serial number of a TwinSAFE terminal

EL1904 Version: 3.1.1 49

Maintenance and cleaning

7 Maintenance and cleaning

Cleaning by the manufacturer only
Do not operate the TwinSAFE component if it is unacceptably dirty. Refer to the technical data for
the protection class.
Send unacceptably dirty TwinSAFE component to the manufacturer for cleaning.

TwinSAFE components are basically maintenance-free.

50 Version: 3.1.1 EL1904

 Decommissioning

8 Decommissioning

8.1 Disposal
NOTICE
Correct disposal
Observe the applicable national laws and guidelines for disposal.
Incorrect disposal may result in environmental damage.

Remove the TwinSAFE component for disposal.

Depending on your application and the products used, make sure that the respective components are
disposed of properly:

Cast iron and metal

Hand over cast iron and metal parts to scrap metal recycling.

Cardboard, wood and polystyrene

Dispose of packaging materials made of cardboard, wood or Styrofoam in accordance with regulations.

Plastic and hard plastic

You can recycle parts made of plastic and hard plastic via the waste management center or reuse them in
accordance with the component regulations and markings.

Oils and lubricants

Dispose of oils and lubricants in separate containers. Hand over containers to the waste oil collection point.

Batteries and accumulators

Batteries and accumulators may also be marked with the crossed-out wheeled garbage can symbol. You
must separate these components from waste. You are legally obliged to return used batteries and
accumulators within the EU. Outside the validity of the EU Directive 2006/66/EC, observe the respective
regulations.

8.1.1 Returning to the vendor

In accordance with the WEEE-2012/19/EU directives, you can return used devices and accessories for
professional disposal. The transport costs are borne by the sender.

Send the used devices with the note "For disposal" to:

Beckhoff Automation GmbH & Co. KG

Gebäude „Service“
Stahlstraße 31
D-33415 Verl

In addition, you have the option to contact a local certified specialist company for the disposal of used
electrical and electronic appliances. Dispose of the old components in accordance with the regulations
applicable in your country.

EL1904 Version: 3.1.1 51

Appendix

9 Appendix

9.1 Volatility
If there are requirements concerning the volatility of products in your application, for example of the U.S.
Department of Defense or similar authorities or security organizations, the following process applies:

The product has both volatile and non-volatile components. Volatile components lose their data immediately
after removing power. Non-volatile components keep the data even after loss of power.

If there is customer specific data saved on the product, it cannot be ensured that this data might not be
restored through for example forensic measures, even after the data is deleted through the provided tool
chain. If this data is confidential, the scrapping of the product after usage is recommended to protect this
data.

52 Version: 3.1.1 EL1904

 Appendix

9.2 Focus of certificates

The most decisive document for certified components of the TwinSAFE department is the EC type
examination certificate. The document contains both the test coverage and the regarded component and
component family.

The current certificates of all TwinSAFE components with the underlying standards and directives can be
found at https://www.beckhoff.com/en-en/support/download-finder/certificates-approvals/.

If the document refers only to the first four figures of a product (ELxxxx), the certificate is valid for all
available variants of the component (ELxxxx-abcd). This is applicable for all components like EtherCAT
Terminals, EtherCAT Boxes, EtherCAT plug-in modules and Bus Terminals.

If you regard the example EL1918 in the picture, the certificate is valid for both the EL1918 and the available
variant EL1918-2200.

EL1904 Version: 3.1.1 53

Appendix

9.3 Certificate

Fig. 27: EL1904 EC declaration of conformity

54 Version: 3.1.1 EL1904

 Table of figures

Table of figures
Fig. 1 Slot and key system and screwless (spring-loaded) connection system. .................................... 14
Fig. 2 Bus Coupler (EtherCAT) .............................................................................................................. 15
Fig. 3 TwinSAFE Terminals (EtherCAT) ................................................................................................ 16
Fig. 4 EL1904 – TwinSAFE terminal with 4 digital fail-safe inputs ......................................................... 19
Fig. 5 Characteristic curve of the inputs................................................................................................. 24
Fig. 6 Dimensions of the EL1904 ........................................................................................................... 25
Fig. 7 Block diagram of the EL1904 ....................................................................................................... 25
Fig. 8 Installation position and minimum distances................................................................................ 27
Fig. 9 Example configuration for temperature measurement ................................................................. 28
Fig. 10 Installation on the mounting rail ................................................................................................... 29
Fig. 11 Removal from mounting rail ......................................................................................................... 30
Fig. 12 PE power contact ......................................................................................................................... 31
Fig. 13 Connection of a cable to a terminal point..................................................................................... 32
Fig. 14 EL1904 pin assignment................................................................................................................ 33
Fig. 15 Permitted cable length ................................................................................................................. 34
Fig. 16 Cable routing................................................................................................................................ 34
Fig. 17 Typical course of test pulses of the inputs ................................................................................... 35
Fig. 18 Typical response time .................................................................................................................. 36
Fig. 19 Worst case response time............................................................................................................ 37
Fig. 20 Inserting an EL1904 ..................................................................................................................... 40
Fig. 21 Address settings on TwinSAFE terminals with 65535 possible addresses.................................. 41
Fig. 22 Entering the FSoE address .......................................................................................................... 42
Fig. 23 Setting the connection of the TwinSAFE connection ................................................................... 43
Fig. 24 Setting the parameters of the TwinSAFE connection .................................................................. 43
Fig. 25 Maximum permissible sensor self-test duration of 350 µs ........................................................... 44
Fig. 26 Unique serial number of a TwinSAFE terminal ............................................................................ 49
Fig. 27 EL1904 EC declaration of conformity........................................................................................... 54

EL1904 Version: 3.1.1 55

More Information:
www.beckhoff.com/EL1904

Beckhoff Automation GmbH & Co. KG

Hülshorstweg 20
33415 Verl
Germany
Phone: +49 5246 9630
info@beckhoff.com
www.beckhoff.com