Beckhoff ELX3351 Operating Manual

Operating manual

ELX3351

1-channel analog input terminal for strain gauge, 16 bit, Ex i

Version:
Date:

1.3.1
2019-01-15

Table of contents

Table of contents

1 Foreword ....................................................................................................................................................5

1.1 Notes on the documentation........................................................................................................... 5

1.2 Safety instructions .......................................................................................................................... 6

1.3 Documentation Issue Status........................................................................................................... 7

1.4 Marking of ELX terminals................................................................................................................ 8

2 Product overview.....................................................................................................................................11

2.1 ELX3351 - Introduction ................................................................................................................. 11

2.2 Technical data .............................................................................................................................. 12

2.3 Intended use ................................................................................................................................. 13

3 Mounting and wiring ...............................................................................................................................14

3.1 Special conditions of use for ELX terminals ................................................................................. 14

3.2 Installation notes for ELX terminals .............................................................................................. 14

3.3 Arrangement of ELX terminals within a bus terminal block .......................................................... 16

3.4 Installation position and minimum distances ................................................................................ 19

3.5 Installation of ELX terminals on mounting rails............................................................................. 20

3.6 Connection.................................................................................................................................... 21

3.6.1 Connection system...........................................................................................................21

3.6.2 Wiring...............................................................................................................................22

3.6.3 Proper line connection .....................................................................................................23

3.6.4 Shielding and potential separation...................................................................................23

3.6.5 ELX3351 - Contact assignment .......................................................................................24

4 Basic function principles........................................................................................................................26

4.1 EtherCAT basics........................................................................................................................... 26

4.2 Basic principles of strain gauge technology.................................................................................. 26

5 Parameterization and programming ......................................................................................................33

5.1 Basics of the measurement functions........................................................................................... 33

5.1.1 General notes ..................................................................................................................33

5.1.2 Block diagram ..................................................................................................................35

5.1.3 Software filter ...................................................................................................................35

5.1.4 Dynamic filter ...................................................................................................................37

5.1.5 Calculating the weight......................................................................................................38

5.2 Application notes .......................................................................................................................... 38

5.2.1 Wiring fail indication .........................................................................................................38

5.2.2 InputFreeze......................................................................................................................38

5.2.3 Gravity adaptation............................................................................................................39

5.2.4 Idling recognition..............................................................................................................40

5.2.5 Official calibration capability.............................................................................................40

5.3 Calibration and compensation ...................................................................................................... 40

5.3.1 Sensor calibration ............................................................................................................41

5.3.2 Self-calibration .................................................................................................................43

5.3.3 Taring...............................................................................................................................44

5.3.4 Overview of commands....................................................................................................44

5.4 Notices on analog specifications .................................................................................................. 45

5.4.1 Full scale value (FSV)......................................................................................................45

5.4.2 Measuring error/ measurement deviation ........................................................................45

5.4.3 Temperature coefficient tK [ppm/K] .................................................................................46

5.4.4 Single-ended/differential typification ................................................................................47

ELX3351 3Version: 1.3.1

Table of contents

5.4.5 Common-mode voltage and reference ground (based on differential inputs)..................50

5.4.6 Dielectric strength ............................................................................................................50

5.4.7 Temporal aspects of analog/digital conversion................................................................51

5.5 Process data................................................................................................................................. 54

5.5.1 Selection of process data.................................................................................................54

5.5.2 Default process image .....................................................................................................55

5.5.3 Variants Predefined PDO.................................................................................................57

5.5.4 Sync Manager..................................................................................................................58

5.6 ELX3351 - Object description and parameterization .................................................................... 59

5.6.1 Restore object..................................................................................................................59

5.6.2 Configuration data............................................................................................................60

5.6.3 Command object..............................................................................................................61

5.6.4 Input data .........................................................................................................................61

5.6.5 Output data ......................................................................................................................61

5.6.6 Information / diagnostic data............................................................................................62

5.6.7 Standard objects ..............................................................................................................62

6 Appendix ..................................................................................................................................................68

6.1 EtherCAT AL Status Codes .......................................................................................................... 68

6.2 UL notice....................................................................................................................................... 68

6.3 Support and Service ..................................................................................................................... 69

ELX33514 Version: 1.3.1

Foreword

1 Foreword

1.1 Notes on the documentation

Intended audience

This description is only intended for the use of trained specialists in control and automation engineering who
are familiar with the applicable national standards.
It is essential that the documentation and the following notes and explanations are followed when installing
and commissioning these components.
It is the duty of the technical personnel to use the documentation published at the respective time of each
installation and commissioning.

The responsible staff must ensure that the application or use of the products described satisfy all the
requirements for safety, including all the relevant laws, regulations, guidelines and standards.

Disclaimer

The documentation has been prepared with care. The products described are, however, constantly under
development.

We reserve the right to revise and change the documentation 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 this documentation.

Trademarks

Beckhoff®, TwinCAT®, EtherCAT®, EtherCATP®, SafetyoverEtherCAT®, TwinSAFE®, XFC® and XTS® are
registered trademarks of and licensed by Beckhoff Automation GmbH.
Other designations used in this publication may be trademarks whose use by third parties for their own
purposes could violate the rights of the owners.

Patent Pending

The EtherCAT Technology is covered, including but not limited to the following patent applications and
patents: EP1590927, EP1789857, DE102004044764, DE102007017835 with corresponding applications or
registrations in various other countries.

The TwinCAT Technology is covered, including but not limited to the following patent applications and
patents: EP0851348, US6167425 with corresponding applications or registrations in various other countries.

EtherCAT® is registered trademark and patented technology, licensed by Beckhoff Automation GmbH,
Germany.

Copyright

© Beckhoff Automation GmbH & Co. KG, Germany.
The reproduction, distribution and utilization of this document as well as the communication of its contents to
others 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.

ELX3351 5Version: 1.3.1

Foreword

1.2 Safety instructions

Safety regulations

Please note the following safety instructions and explanations!
Product-specific safety instructions can be found on following pages or in the areas mounting, wiring,
commissioning etc.

Exclusion of liability

All the components are supplied in particular hardware and software configurations appropriate for the
application. Modifications to hardware or software configurations other than those described in the
documentation are not permitted, and nullify the liability of Beckhoff Automation GmbH & Co. KG.

Personnel qualification

This description is only intended for trained specialists in control, automation and drive engineering who are
familiar with the applicable national standards.

Description of instructions

In this documentation the following instructions are used.
These instructions must be read carefully and followed without fail!

DANGER

WARNING

CAUTION

Attention

Note

Serious risk of injury!

Failure to follow this safety instruction directly endangers the life and health of persons.

Risk of injury!

Failure to follow this safety instruction endangers the life and health of persons.

Personal injuries!

Failure to follow this safety instruction can lead to injuries to persons.

Damage to environment/equipment or data loss

Failure to follow this instruction can lead to environmental damage, equipment damage or
data loss.

Tip or pointer

This symbol indicates information that contributes to better understanding.

ELX33516 Version: 1.3.1

1.3 Documentation Issue Status

Version Comment

1.3.1 • Minor corrections at chapter Basic function principles and Parameterization and
programming during translation

1.3.0 • Chapter Basic function principles added

• Chapter Parameterization and programming added

1.2.0 • Connection extended with sensor display

• Chapter Configuration of ELX terminals in Bus Terminal block updated

• Chapter Identification of ELX terminals updated

• Technical data updated

1.1.0 • Chapter Configuration of ELX terminals in Bus Terminal block updated

1.0.1 • Layout updated

1.0 • Technical data updated

• Chapter Mounting and wiring updated

0.2 • Technical data updated

• Chapter Mounting and wiring updated

0.1 • First preliminary version (for internal use only)

Foreword

ELX3351 7Version: 1.3.1

Foreword

1.4 Marking of ELX terminals

Name

An ELX terminal has a 15-digit technical designation, composed of

• family key

• type

• software variant

• revision

example family type software variant revision

ELX1052-0000-0000 ELX terminal 1052: two-channel digital input terminal

for NAMUR sensors, Ex i

ELX9650-0000-0000 ELX terminal 9650: power supply terminal 0000: basic type 0001

Notes

• The elements mentioned above result in the technical designation. ELX1052-0000-0001 is used in
the example below.

• Of these, ELX1052-0000 is the order identifier, commonly called just ELX1052 in the "-0000" revision.
“-0001” is the EtherCAT revision.

• The order identifier is made up of

- family key (ELX)

- type (1052)

- software version (-0000)

• The Revision -0001 shows the technical progress, such as the extension of features with regard to the
EtherCAT communication, and is managed by Beckhoff.
In principle, a device with a higher revision can replace a device with a lower revision, unless specified
otherwise, e.g. in the documentation.
Associated and synonymous with each revision there is usually a description (ESI, EtherCAT Slave
Information) in the form of an XML file, which is available for download from the Beckhoff website.
The revision has been applied to the terminals on the outside, see ELX1052 with date code

3218FMFM, BTN 10000100 and Ex marking.

• The hyphen is omitted in the labeling on the side of the terminal. Example:
Name: ELX1052-0000
Label: ELX1052

• The type, software version and revision are read as decimal numbers, even if they are technically
saved in hexadecimal.

0000

0000: basic type 0001

Identification numbers

ELX terminals have two different identification numbers:

• date code (batch number)

• Beckhoff Traceability Number, or BTN for short (as a serial number it clearly identifies each terminal)

Datecode

The date code is an eight-digit number given by Beckhoff and printed on the ELX terminal. The date code
indicates the build version in the delivery state and thus identifies an entire production batch, but does not
distinguish between the terminals in a batch.

Structure of the date code: WWYYFFHH

WW - week of production (calendar week)
YY - year of production
FF - firmware version
HH - hardware version

ELX33518 Version: 1.3.1

Example with date code: 02180100:
02 - week of production 02
18 - year of production 2018
01 - firmware version 01
00 - hardware version 00

Beckhoff Traceability Number (BTN)

In addition, each ELX terminal has a unique Beckhoff Traceability Number (BTN).

Ex marking

The Ex marking can be found at the top left on the terminal:

II 3 (1) G Ex ec [ia Ga] IIC T4 Gc
II (1) D [Ex ia Da] IIIC
I (M1) [Ex ia Ma] I
IECEx BVS 18.0005X
BVS 18 ATEX E 005 X

Examples

Foreword

Fig.1: ELX1052-0000 with date code 32180000, BTN 10000100 and Ex marking

ELX3351 9Version: 1.3.1

Foreword

Fig.2: ELX9012 with date code 32180005 and Ex marking

ELX335110 Version: 1.3.1

2 Product overview

2.1 ELX3351 - Introduction

Product overview

Fig.3: 1-channel analog input terminal for strain gauge, 16 bit, Ex i

The analog ELX3351 input terminal enables direct connection of a resistor bridge or load cell from
hazardous areas, Zone 0/20 and 1/21. The terminal can be connected in 4- or 6-wire technology. The ratio
between the bridge voltage UD and the supply voltage UR is determined in 24-bit resolution, and the load
value is calculated as a process value. Apart from automatic self-calibration (can be deactivated), additional
functions such as Tara and Freeze as well as dynamic filters are integrated.

ELX3351 11Version: 1.3.1

Product overview

2.2 Technical data

Technical data ELX3351-0000

Sensor types resistor bridge, strain gauge
Number of inputs 1, for 1 resistor bridge in full bridge technology
Connection method 4-wire, 6-wire
Bridge input resistance 300Ω…1.5kΩ
Measuring range U
Measuring range U

D

REF

Internal resistance > 25kΩ (UR, differential), > 1MΩ (UD, differential)
Resolution 24Bit, 32bit presentation
Measuring error < ±0,5 % (relative to full scale value), self-calibration active
Input filter limit frequency typ. 3.6kHz (-3dB, low pass)
Conversion time typ. 1.6 ms
Filter 50Hz, configurable
Supply voltage electronics via E-Bus (5VDC) and Power Contacts (24V

Current consumption from E-Bus typ. 85mA
Power supply U

V

Current consumption power contacts min. 20mA, dependent on sensor
Special features self-calibration, dynamic filters, freeze
Bit width in the process image 32 bit
Electrical isolation 1500V (E-Bus/ field voltage)
Weight app. 60g
Permissible ambient temperature range

during operation
Permissible ambient temperature range

during storage
Permissible relative humidity 95%, no condensation
Permissible air pressure

(operation, storage, transport)

Dimensions (W x H x D) app. 15mm x 100mm x 70mm (width aligned: 12mm)
Mounting on 35mm mounting rail conforms to EN 60715
Vibration/ shock resistance conforms to EN60068-2-6/ EN60068-2-27
EMC immunity/ emission conforms to EN61000-6-2/ EN61000-6-4
Protect. class IP20
Permissible installation position

Approvals CE, ATEX, IECEx

max. -18…+18mV
max. -12…+12V

Ex, feeding by

DC

ELX9560)

up to 10VDC, dependent on sensor

-25°C ... + 60°C

-40°C ... + 85°C

800hPa to 1100hPa
(this corresponds to a height of approx. -690m to 2000m over
sea level assuming an international standard atmosphere)

See chapter Installation position and minimum distances [}19]

ELX335112 Version: 1.3.1

Technical data for explosion protection ELX3351-0000

Ex marking II 3 (1) G Ex ec [ia Ga] IIC T4 Gc

II (1) D [Ex ia Da] IIIC
I (M1) [Ex ia Ma] I

Certificate numbers IECEx BVS 18.0005X

BVS 18 ATEX E 005 X
Power supply Invariable in connection with ELX9560
Field interfaces UO = 11.76V

IO = 146mA

PO = 214mW

Characteristic curve: linear
Reactance (without

consideration of the
simultaneousness)

Ex ia I 20mH 40µF
Ex ia IIA 13.3mH 39µF
Ex ia IIB 6.6mH 9.9µF
Ex ia IIC 1.7mH 1.5µF
Ex ia IIIC 6.6mH 9.9µF

L

0

C

0

Product overview

2.3 Intended use

Endangering the safety of persons and equipment!

The ELX components may only be used for the purposes described below!

WARNING

Observe ATEX and IECEx!

The ELX components may only be used in accordance with the ATEX directive and the

CAUTION

The ELX terminals extend the field of application of the Beckhoff bus terminal system with functions for
integrating intrinsically safe field devices from hazardous areas. The intended field of application is data
acquisition and control tasks in discrete and process engineering automation, taking into account explosion
protection requirements.

The ELX terminals are protected by the type of protection "Increased safety" (Exe) according to
IEC60079-7 and must only be operated in hazardous areas of Zone2 or in non-hazardous areas.

The field interfaces of the ELX terminals achieve explosion protection through the type of protection "intrinsic
safety" (Exi) according to IEC60079-11. For this reason, only appropriately certified, intrinsically safe
devices may be connected to the ELX terminals. Observe the maximum permissible connection values for
voltages, currents and reactances. Any infringement can damage the ELX terminals and thus eliminate the
explosion protection.

IECEx scheme!

The ELX terminals are open, electrical equipment for installation in lockable cabinets, enclosures or
operating rooms. Make sure that access to the equipment is only possible for authorized personnel.

Ensure traceability!

The buyer has to ensure the traceability of the device via the Beckhoff Traceability Number

CAUTION

ELX3351 13Version: 1.3.1

(BTN) [}9].

Mounting and wiring

3 Mounting and wiring

3.1 Special conditions of use for ELX terminals

Observe the special conditions of use for the intended use of Beckhoff ELX
terminals in potentially explosive areas (ATEX directive 2014/34/EU)!

WARNING

• The certified components are to be installed in a suitable housing that guarantees an
ingress protection of at least IP54 in accordance with EN60079-0 and EN60529! The
prescribed environmental conditions during installation, operation and maintenance are
thereby to be taken into account! Inside the housing, pollution degree 1 and 2 are per­missible.

• 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 -25 to +60°C of Beckhoff ELX
terminals!

• Measures must be taken to protect against the rated operating voltage being exceeded
by more than 40% due to short-term interference voltages! The power supply of the
ELX9560 power supply terminal must correspond to overvoltage categoryII according
to EN60664-1

• The individual terminals may only be unplugged or removed from the bus terminal sys­tem if all supply voltages have been switched off or if a non-explosive atmosphere is
ensured!

• The connections of the ELX9560 power supply terminal may only be connected or dis­connected if all supply voltages have been switched off or if a non-explosive atmos­phere is ensured!

• The fuses of the EL92xx power feed terminals may only be exchanged if all supply volt­ages have been switched off or if a non-explosive atmosphere is ensured!

• Address selectors and switches may only be adjusted if all supply voltages have been
switched off or if a non-explosive atmosphere is ensured!

3.2 Installation notes for ELX terminals

Storage, transport and mounting

• Transport and storage are permitted only in the original packaging!

Attention

WARNING

• Store in a dry place, free from vibrations.

• A brand new ELX terminal with a certified build version is delivered only in a sealed car­ton. Therefore, check that the carton and all seals are intact before unpacking.

• Do not use the ELX terminal if

- its packaging is damaged

- the terminal is visibly damaged or

- you cannot be sure of the origin of the terminal.

• ELX terminals with a damaged packaging seal are regarded as used.

Observe the accident prevention regulations

During mounting, commissioning, operation and maintenance, adhere to the safety regula­tions, accident prevention regulations and general technical rules applicable to your de­vices, machines and plants.

ELX335114 Version: 1.3.1

CAUTION

Attention

Attention

Attention

Mounting and wiring

Observe the erection regulations

Observe the applicable erection regulations.

Protect the terminals against electrostatic discharge (ESD)

Electronic components can be destroyed by electrostatic discharge. Therefore, take the
safety measures to protect against electrostatic discharge as described in DIN EN
61340-5-1 among others. In conjunction with this, ensure that the personnel and surround­ings are suitably earthed.

Do not place terminals on E-bus contacts

Do not place the ELX terminals on the E-bus contacts located on the right-hand side. The
function of the E-bus contacts can be negatively affected by damage caused by this, e.g.
scratches.

Protect the terminals against dirt

To ensure the functionality of the ELX terminals they must be protected against dirt, espe­cially on the contact points. For this reason use only clean tools and materials.

Handling

• It is forbidden to insert conductive or non-conductive objects of any kind into the interior

Attention

If an ELX terminal is defective or damaged it must be replaced by an equivalent terminal. Do not carry out
any repairs to the devices. For safety reasons repairs may only be carried out by the manufacturer.

of the housing (e.g. through the ventilation slots in the housing).

• Use only the openings provided in the housing front and appropriate tools to actuate the
spring-loaded terminal contacts on the front side for attaching connection cables to the

terminal; see chapter Wiring [}22].

• The opening of the housing, the removal of parts and any mechanical deformation or
machining of an ELX terminal are not permitted!

Contact marking and pin assignment

The colored inscription labels above the front connection contacts shown in the illustrations

Attention

in the introduction chapter are only examples and are not part of the scope of delivery!
A clear assignment of channel and terminal designation according to the chapter contact
assignment to the actual terminal point can be made via the lasered channel numbers 1 to
8 on the left above the respective terminal point as well as via the laser image.
Observe any possible polarity dependency of connected intrinsically safe circuits!

ELX3351 15Version: 1.3.1

Mounting and wiring

3.3 Arrangement of ELX terminals within a bus terminal block

Observe the following instructions for the arrangement of ELX terminals!

• ELX signal terminals must always be installed behind an ELX9560 power supply termi-

WARNING

Examples for the arrangement of ELX terminals

nal, without exception!

• Only signal terminals of the ELX series may be installed behind an ELX9560 power
supply terminal!

• Multiple ELX9560 power supply terminals may be set in one terminal block as long as
one ELX9410 is placed before each additional ELX9560!

• An ELX9410 power supply terminal must not be mounted to the right of an ELX9560
nor to the left of any ELX signal terminal!

• The last terminal of each ELX segment is to be covered by an ELX9012 bus end cover,
unless two ELX9410 power supply terminals are installed in direct succession for con­tinuing the same terminal segment with standard Beckhoff EtherCAT terminals (e.g. EL/
ES/EK)!

Fig.4: Valid arrangement of the ELX terminals (right terminal block).

Fig.5: Valid arrangement - terminals that do not belong to the ELX series are set before and after the ELX
terminal segment. The separation is realized by the ELX9560 at the beginning of the ELX terminal segment
and two ELX9410 at the end of the ELX terminal segment.

Fig.6: Valid arrangement - multiple power supplies by ELX9560, each with an upstream ELX9410.

ELX335116 Version: 1.3.1

Fig.7: Valid arrangement - ELX9410 in front of an ELX9560 power supply terminal.

Mounting and wiring

Fig.8: Invalid arrangement - missing ELX9560 power supply terminal.

Fig.9: Invalid arrangement - terminal that does not belong to the ELX series within the ELX terminal
segment.

Fig.10: Invalid arrangement - second ELX9560 power supply terminal within the ELX terminal segment
without an upstream ELX9410.

ELX3351 17Version: 1.3.1

Mounting and wiring

Fig.11: Invalid arrangement - missing ELX9012 bus end cover.

Observe the maximum output current of the ELX9560

When configuring the ELX terminal segment, please note the maximum available output

Attention

current of the ELX9560 power supply terminal in accordance with the specified technical
data.
If required, an additional power supply terminal ELX9560 with an upstream ELX9410 con­nected (see mounting examples) must be installed or a completely new terminal block must
be assembled.

ELX335118 Version: 1.3.1

Mounting and wiring

3.4 Installation position and minimum distances

Installation position

For the prescribed installation position the mounting rail is installed horizontally and the mating surfaces of
the ELX 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.

Minimum distances

Observe the following minimum distances to ensure optimum convection cooling:

• above and below the ELX terminals: 35mm (required!)

• besides the bus terminal block: 20mm (recommended)

Fig.12: Installation position and minimum distances

Observe the minimum separation distances according to IEC 60079-14!

Observe the prescribed minimum separation distances between intrinsically safe and non-

WARNING

ELX3351 19Version: 1.3.1

intrinsically safe circuits according to IEC 60079-14.

Mounting and wiring

3.5 Installation of ELX terminals on mounting rails

Risk of electric shock and damage of device!

Bring the bus terminal system into a safe, powered down state before starting installation,

WARNING

CAUTION

Assembly

disassembly or wiring of the bus terminals!

Danger of injury due to power contacts!

For your own protection, pay attention to careful and careful handling of the ELX terminals.
In particular, the left side mounted, sharp-edged blade contacts pose a potential risk of in­jury.

Fig.13: Attaching on mounting rail

The bus coupler and bus terminals are attached to commercially available 35mm mounting rails (DIN rails
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 tongue and groove 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 tongue and
groove, the connection will not be operational! When correctly assembled, no significant gap should
be visible between the housings.

Fixing of mounting rails

The locking mechanism of the terminals and couplers extends to the profile of the mounting

Note

rail. At the installation, the locking mechanism of the components must not come into con­flict with the fixing bolts of the mounting rail. To mount the mounting rails with a height of

7.5mm under the terminals and couplers, you should use flat mounting connections (e.g.
countersunk screws or blind rivets).

ELX335120 Version: 1.3.1

Mounting and wiring

Disassembly

Fig.14: Disassembling of terminal

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

1. Pull the terminal by its orange-colored lugs approximately 1cm away from the mounting rail. In doing
so for this terminal the mounting rail lock is released automatically and you can pull the terminal out of
the bus terminal block easily without excessive force.

2. Grasp the released terminal with thumb and index finger simultaneous at the upper and lower grooved
housing surfaces and pull the terminal out of the bus terminal block.

Connections within a bus terminal block

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

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

• 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 of the ELX terminals are supplied by the ELX9560 power terminal. This interrupts
the power contacts and thus represents the beginning of a new supply rail.

Power Contacts

During the design of a bus terminal block, the pin assignment of the individual Bus Termi-

Note

nals must be taken account of, since some types (e.g. analog Bus Terminals or digital 4­channel Bus Terminals) do not or not fully loop through the power contacts.

3.6 Connection

3.6.1 Connection system

Risk of electric shock and damage of device!

Bring the bus terminal system into a safe, powered down state before starting installation,

WARNING

ELX3351 21Version: 1.3.1

disassembly or wiring of the bus terminals!

Mounting and wiring

Overview

The terminals of ELXxxxx series with standard wiring include electronics and connection level in a single
enclosure.

Standard wiring (ELXxxxx)

Fig.15: Standard wiring

The terminals of ELXxxxx series feature integrated screwless spring force technology for fast and simple
assembly.

Ultrasonically "bonded" (ultrasonically welded) conductors

Ultrasonically “bonded" conductors

It is also possible to connect the Standard Terminals with ultrasonically "bonded" (ultrasoni-

Note

cally welded) conductors. In this case, please note the tables concerning the wire-size
width below!

3.6.2 Wiring

Risk of electric shock and damage of device!

Bring the bus terminal system into a safe, powered down state before starting installation,

WARNING

Terminals for standard wiring ELXxxxx

disassembly or wiring of the Bus Terminals!

Fig.16: Connecting a cable on a terminal point

ELX335122 Version: 1.3.1

Mounting and wiring

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 point closes automatically when the pressure is released, holding the wire securely and
permanently.

Observe the requirements for connecting cables and cross sections according to IEC 60079-7 and IEC
60079-11. See the following tables for the suitable wire size width.

Power supply terminal ELX9560
Wire size width (single core wires) 0.14 ... 1.5mm
Wire size width (fine-wire conductors) 0.14 ... 1.5mm
Wire size width (conductors with a wire end sleeve) 0.14 ... 1.0mm

2

2

2

Wire stripping length 8 ... 9mm

Maximum screwdriver width for ELX9560

Use a screwdriver with a maximum width of 2mm to wire the ELX9560 power supply termi-

Attention

nal. Wider screwdrivers can damage the terminal points.

All other ELX terminals ELXxxxx
Wire size width (single core wires) 0.08 ... 2.5mm
Wire size width (fine-wire conductors) 0.08 ... 2.5mm
Wire size width (conductors with a wire end sleeve) 0.14 ... 1.5mm

2

2

2

Wire stripping length 8 ... 9mm

3.6.3 Proper line connection

Always connect only one wire per terminal point.

When using fine-wire conductors it is recommended to connect them with wire end sleeves in order to
establish a safe, conductive connection.

In addition, make sure that the pin assignment is correct to prevent damage to the ELX terminals and the
connected devices.

3.6.4 Shielding and potential separation

Shielding

Encoder, analog sensors and actors should always be connected with shielded, twisted

Note

paired wires.

Observe installation requirements in areas of potentially explosive atmos­pheres!

CAUTION

During installation, observe the requirements for cables, shielding and earth potential
equalization in areas of potentially explosive atmospheres according to IEC60079-11,
IEC60079-14 and IEC60079-25.

Ensure potential separation of the 24V Ex busbar!

In any case, make sure that the galvanic isolation made by the ELX9560 between the 24V

WARNING

ELX3351 23Version: 1.3.1

Ex busbar (power contacts +24VEx and 0VEx) and other system potentials (if applicable
also functional or protective earths) is not removed.

Mounting and wiring

3.6.5 ELX3351 - Contact assignment

Fig.17: ELX3351 - Contact assignment

Terminal point Description

Name No.

1 not implemented
+U
+ U
+U

D

R

V

2 + input measuring voltage (difference voltage of bridge)

3 + input reference voltage (supply voltage at bridge)

4 + output supply voltage for bridge

5 not implemented

-U

- U

- U

D

R

V

6 - input measuring voltage (difference voltage of bridge)

7 - input reference voltage (supply voltage at bridge)

8 - output supply voltage for bridge

ELX335124 Version: 1.3.1

Wiring the bridge

Fig.18: ELX3351 - Connection of a full bridge in 6-wire technology

Mounting and wiring

The ELX3351 is standardly designed for a sensor connection in 6-wire technology.
In the event that a sensor is to be operated in 4-wire technology, the contacts +UV and +UR as well as the
contacts -UV and -UR are to be bridged manually, a software-side switching within the terminal is not
possible.

The terminal supplies 10VDC bridge supply voltage UV in not loaded state. This voltage is still limited to UO in
accordance with the Technical Data for Explosion Protection [}13].

The maximum measuring input voltage U

is limited to 12VDC, the input measuring voltage is limited to

REF

18mVDC.

LED Display

LED Color Meaning

Run green These LED indicates the terminal's operating state:

off State of the EtherCAT State Machine: INIT=initialization of the terminal
flashing State of the EtherCAT State Machine: PREOP = function for mailbox

communication and different standard-settings set

single
flash

State of the EtherCAT State Machine: SAFEOP = verification of the Sync
Manager channels and the distributed clocks.
Outputs remain in safe state

on State of the EtherCAT State Machine: OP = normal operating state;

mailbox and process data communication is possible

flickering State of the EtherCAT State Machine: BOOTSTRAP = function for

firmware updates of the terminal

Error red on There is a fault (eg. undershooting or exceeding the measured value

range)

Note: Wire break detection is only for the +Uv and -Uv connections
Measuring green on The terminal is in normal operating mode (measurement)
Self calibration green on Self-calibration in operation

ELX3351 25Version: 1.3.1

Basic function principles

4 Basic function principles

4.1 EtherCAT basics

Please refer to the EtherCAT System Documentation for the EtherCAT fieldbus basics, also available as PDF
file from www.beckhoff.com.

4.2 Basic principles of strain gauge technology

Basic information on the technological field of strain gauges/load cells as metrological instruments is to be
given below. The information is of general nature; it is up to the user to check the extent to which it applies to
his application.

• Strain gauges serve either to directly measure the static (0 to a few Hz) or dynamic (up to several KHz)
elongations, compressions or torsions of a body by being directly fixed to it, or to measure various
forces or movements as part of a sensor (e.g. load cells/force transducers, displacement sensor,
vibration sensors).

• In the case of the optical strain gauge (e.g. Bragg grating), an application of force causes a
proportional change in the optical characteristics of a fiber used as a sensor. Light with a certain
wavelength is fed into the sensor. Depending upon the deformation of the grating, which is laser-cut
into the sensor, due to the mechanical load, part of the light is reflected and evaluated using a suitable
measuring transducer (interrogator).

The commonest principle in the industrial environment is the electrical strain gauge. There are many
common terms for this type of sensor: load cell, weighbridge, etc.

Structure of electrical strain gauges

A strain gauge consists of a carrier material (e.g. stretchable plastic film) with an applied metal film from
which a lattice of electrically conductive resistive material is worked in very different geometrical forms,
depending on the requirements.

Fig.19: Strain gauge

This utilizes a behavior whereby, for example in the case of strain, the length of a metallic resistance network
increases and its diameter decreases, as a result of which its electrical resistance increases proportionally.

ΔR/R = k*ε

ε = Δl/l thereby corresponds to the elongation; the strain sensitivity is called the k-factor. This also gives rise
to the typical track layout inside the strain gauge: the resistor track or course is laid in a meandering pattern
in order to expose the longest possible length to the strain.

Example

The elongation ε = 0.1% of a strain gauge with k-factor 2 causes an increase in the resistance of 0.2%.
Typical resistive materials are constantan (k~2) or platinum tungsten (92PT, 8W with k ~4). In the case of
semiconductor strain gauges a silicon structure is glued to a carrier material. The conductivity is changed
primarily by deformation of the crystal lattice (piezo-resistive effect). k-factors of up to 200 can be achieved.

ELX335126 Version: 1.3.1

Basic function principles

Measurement of signals

The change in resistance of an individual strain gauge can be determined in principle by resistance
measurement (current/voltage measurement) using a 2/3/4-wire measurement technique.

Usually 1/2/4 strain gauges are arranged in a Wheatstone bridge (-> quarter/half/full bridge); the nominal
resistance/impedance R0 of all strain gauges (and the auxiliary resistors used if necessary) is usually
equivalent to R1=R2=R3=R4=R0. Typical values in the non-loaded state are R0=120Ω, 350Ω, 700Ω and
1kΩ.

The full bridge possesses the best characteristics such as linearity in the feeding of current/voltage, four
times the sensitivity of the quarter-bridge as well as systematic compensation of disturbing influences such
as temperature drift and creeping. In order to achieve high sensitivity, the 4 individual strain gauges are
arranged on the carrier in such a way that 2 are elongated and 2 are compressed in each case.

Fig.20: quarter, half, and full bridge

The measuring bridges can be operated with constant current, constant voltage, or also with AC voltage
using the carrier frequency method.

Full bridge strain gauge at constant voltage (ratiometric measurement)

Since the relative resistance change ΔR is low in relation to the nominal resistance R0, a simplified equation
is given for the strain gauge in the Wheatstone bridge arrangement:

UD/UV= ¼ * (ΔR1-ΔR2+ΔR3-ΔR4)/R0.

ΔR usually has a positive sign in the case of elongation and a minus sign in the case of compression.

A suitable measuring instrument measures the bridge supply voltage UV and the resulting bridge voltage UD,
and forms the quotients from both voltages, i.e. the ratio. After further calculation and scaling the measured
value is output, e.g. in kg.

If the voltages UV and UD are measured simultaneously, i.e. at the same moment, and placed in relation to
each other, then this is referred to as a ratiometric measurement.

The advantage of this is that (with simultaneous measurement!) brief changes in the supply voltage (e.g.
EMC effects) or a generally inaccurate or unstable supply voltage likewise have no effect on the
measurement.

A change in UV by e.g. 1% creates the same percentage change in UD according to the above equation. Due
to the simultaneous measurement of UD and UV the error cancels itself out completely during the division.

4-wire vs. 6-wire connection

With a constant voltage supply, the magnitude of the current can be quite considerable, e.g. 12V/ 350
Ω=34.3mA. This leads not only to dissipated heat, wherein the specification of the strain gauge employed
must not be exceeded, but possibly also to measuring errors in the case of inadequate wiring due to line
losses not being taken into account or compensated.

In principle a full bridge can be operated with a 4-conductor connection (2 conductors for the supply UV and 2
for the measurement of the bridge voltage UD).

ELX3351 27Version: 1.3.1

Basic function principles

If, for example, a 25 m copper cable (feed + return = 50 m) with a cross section q of 0.25 mm2 is used, this
results in a line resistance of

RL= l/ (κ * q) = 50 m / (58 S*m/mm2* 0.25 mm2) = 3.5 Ω

If this value remains constant, then the error resulting from it can be calibrated out. However, assuming a
realistic temperature change of, for example, 30° the line resistance RL changes by

ΔRL =30° * 3.9 * 10-4 * 3.5 Ω = 0.41 Ω

In relation to a 350Ω measuring bridge this means a measuring error of > 0.1%.

Fig.21: 4-wire connection

This can be remedied by a 6-wire connection, in particular for precision applications.

Fig.22: 6-wire connection

The supply voltage UV is thereby fed to the strain gauge (= current carrying conductor). The incoming supply
voltage U

is only measured with high impedance directly at the measuring bridge in exactly the same way

Ref

as the bridge voltage UD with two currentless return conductors in each case. The conductor-related errors
are hence omitted.

Since these are very small voltage levels of the order of mV and µV, all conductors should be screened.

ELX335128 Version: 1.3.1

Basic function principles

Structure of a load cell with a strain gauge

One application of the strain gauge is the construction of load cells.

This involves gluing strain gauges (full bridges as a rule) to an elastic mechanical carrier, e.g. a double­bending beam spring element, and additionally covered to protect against environmental influences.

The individual strain gauges are aligned for maximum output signals according to the load direction (2 strain
gauges in the elongation direction and 2 in the compression direction).

Fig.23: Example of a load cell

The most important characteristic data of a load cell

Characteristic data

Please enquire to the sensor manufacturer regarding the exact characteristic data!

Note

Nominal load E

Maximum permissible load for normal operation, e.g. 10kg

Nominal characteristic value mV/V

The nominal characteristic value 2mV/V means that, with a supply of US=10V and at the full load E
load cell, the maximum output voltage UD=10V*2mV/V=20mV. The nominal characteristic value is
always a nominal value – a manufacturer’s test report is included with good load cells stating the
characteristic value determined for the individual load cell, e.g. 2.0782mV/V.

Minimum calibration value V

This indicates the smallest mass that can be measured without the maximum permissible error of the load
cell being exceeded [RevT].

This value is represented either by the equation V
E

(e.g. 0.01).

max

max

min

min

= E

/ n (where n is an integer, e.g. 10000), or in % of

max

max

of the

ELX3351 29Version: 1.3.1

Basic function principles

This means that a load cell with E

V

=10kg / 10000 = 1 g or V

min

= 10kg has a maximum resolution of

max

=10kg*0.01%= 1g.

min

Accuracy class according to OIML R60

The accuracy class is indicated by a letter (A, B, C or D) and an additional number, which encodes the scale
interval d with a maximum number n

(*1000); e.g. C4 means Class C with maximally 4000d scale

max

intervals.

The classes specify a maximum and minimum limit for scale intervals d:

• A: 50,000 – unlimited

• B: 5000 – 100,000

• C: 500 – 10,000

• D: 500 – 1000,

The scale interval n
scales can be built that has a maximum measuring range of 4000d * V

= 4000d states that, with a load cell with a resolution of V

max

= 4kg. Since V

min

= 1g, a calibratable set of

min

is thereby a

min

minimum specification, an 8 kg set of scales could be built – if the application allows – with the same load
cell, wherein the calibratable resolution would then fall to 8 kg/4000d = 2g. From another point of view the
scale interval n

is a maximum specification; hence, the above load cell could be used to build a set of

max

scales with a measuring range of 4 kg, but a resolution of only 2000 divisions = 2g, if this is adequate for the
respective application. Also the classes differ in certain error limits related to non-repeatability/creep/TC.

Accuracy class according to PTB

The European accuracy classes are defined in an almost identical way (source: PTB).

Class Calibration value e Minimum load Max/e

Minimum value Maximum value

I

0.001 g <= e 100 e 50000 -

Fine scales
II

Precision scales
III

Commercial scales
IIII

0,001 g <= e <= 0,05 g
0,1 g <= e

0.1g <= e <= 2g
5 g <= e

20 e
50 e

20 e
20 e

100
5000

100
500

100000
100000

10000
10000

5 g <= e 10 e 100 1000

Coarse scales

Minimum application range or minimum measuring range in % of rated load

This is the minimum measuring range/measuring range interval, which a calibratable load cell/set of scales
must cover.

Example: above load cell E

= 10kg; minimum application range e.g. 40% E

max

max

The used measuring range of the load cell must be at least 4 kg. The minimum application range can lie in
any range between E
structural reasons. A relationship between n

and E

min

, e.g. between 2kg and 6kg if a tare mass of 2kg already exists for

max

max

and V

is thereby likewise apparent:

min

4000 * 1g = 4kg .

There are further important characteristic values, which are for the most part self-explanatory and need not
be discussed further here, such as nominal characteristic value tolerance, input/output resistance,
recommended supply voltage, nominal temperature range etc.

ELX335130 Version: 1.3.1

Basic function principles

Parallel connection of strain gauges

It is usual to distribute a load mechanically to several strain gauge load cells at the same time. Hence, for
example, the 3-point bearing of a silo container on 3 load cells can be realized. Taking into account wind
loads and loading dynamics, the total loading of the silo including the dead weight of the container can thus
be measured. The mechanically parallel-connected load cells are usually also electrically connected in
parallel and to one measuring transducer, e.g. the ELX3351. To this end the following must be observed:

• The load cells must be matched to each other and approved by the manufacturer for this mode of
operation.

• The impedance of the load cells must be such that the current feed capability of the transducer
electronics is not overloaded.

• For parallel connection, the minimum permissible connection resistance to the ELX3351 must be
observed (bridge input resistance according to chapter Technical data [}12]). To ensure explosion

protection, the parallel connection of the individual bridge resistors must not fall below the minimum
value of 300Ω. The individual strain gage bridges do not require safe isolation in accordance with the
requirements of IEC60079-11 and must be regarded as an intrinsically safe circuit (e.g. for the design
of connection cables in accordance with IEC60079-25).

Fig.24: Parallel strain gauge

Sources of error/disturbance variables

Inherent electrical noise of the load cell

Electrical conductors exhibit so-called thermal noise (thermal/Johnson noise), which is caused by irregular
temperature-dependent movements of the electrons in the conductor material. The resolution of the bridge
signal is already limited by this physical effect. The rms value en of the noise can be calculated by
en=√4kTRB.

In the case of a load cell with R0 = 350 Ω at an ambient temperature T=20°C (= 293K) and a bandwidth of
the measuring transducer of 50Hz (and Boltzmann constant k = 1.38 * 10
peak-peak noise epp is thus approx. e

~6.6*en=111nV.

pp

-23

J/K), the rms en= 16.8 nV. The

Example

In relation to the maximum output voltage U
U

= 5V*2mV/V=10mV. (For the nominal load) this results in a maximum resolution of

out_max

of a bridge with 2 mV/V and Us=5V, this corresponds to

out_max

10mV/111nV=90090digits. Converted into bit resolution: ln(90090)/ln(2)~16bits.

ELX3351 31Version: 1.3.1

Basic function principles

Interpretation: a higher digital measuring resolution than 16 bits is thus inappropriate for such an analog
signal in the first step. If a higher measuring resolution is used, then additional measures may need to be
taken in the evaluation chain in order to obtain the higher information content from the signal, e.g. hardware
low-pass filter or software algorithms.

This resolution applies alone to the measuring bridge without any further interferences. The resolution of the
measuring signal can be increased by reducing the bandwidth of the measuring unit.

If the strain gauge is glued to a carrier (load cell) and wired up, both external electrical disturbances (e.g.
thermovoltage at connection points) and mechanical vibrations in the vicinity (machines, drives, transformers
(mechanical and audible 50Hz vibration due to magnetostriction etc.)) can additionally impair the result of
measurement.

Creep

Under a constant load, spring materials can further deform in the load direction. This process is reversible,
but it generates a slowly changing measured value during the static measurement. In an ideal case the error
can be compensated by constructive measures (geometry, adhesives).

Hysteresis

If even elongation and compression of the load cell take place, then the output voltage does not follow
exactly the same curve, since the deformation of the strain gauge and the carrier may be different due to the
adhesive and its layer thickness.

Temperature drift (inherent heating, ambient temperature)

Relatively large currents can flow in strain gauge applications, e.g. I=Us/R0=10V/350Ω=26mA.
The power dissipation at the sensor is thus Pv=U*I=10V*26mA=260mW. Depending on application/
carrier material (= cooling) and ambient temperature, a not insignificant error can arise that is termed
apparent elongation. The sensor manufacturers integrate suitable compensation elements in their strain
gauges.

Inadequate circuit technology

As already shown, a full bridge may be able (due to the system) to fully compensate non-linearity, creep and
temperature drift. Wiring-related measuring errors are avoided by the 6-conductor connection.

References

Some organizations are listed below that provide the specifications or documents for the technological field
of weighing technology:

• OIML (ORGANISATION INTERNATIONALE DE MÉTROLOGIE LÉGALE) www.oiml.org

• PTB - Physikalisch-Technischen Bundesanstalt www.ptb.de

• www.eichamt.de

• WELMEC - European cooperation in legal metrology www.welmec.org

• DKD - Deutscher Kalibrierdienst www.dkd.eu

• Fachgemeinschaft Waagen (AWA) im Verband Deutscher Maschinen- und Anlagenbau VDMA
www.vdma.org

ELX335132 Version: 1.3.1

Parameterization and programming

5 Parameterization and programming

5.1 Basics of the measurement functions

The measuring functions of the ELX3351 can be described as follows:

• The ELX3356 Analog Input Terminal is used to acquire the supply voltage to a load cell as a reference
voltage, and the differential voltage that is proportional to the force acting on the cell.

• A full bridge must be connected. If only a quarter or half bridge is available, external auxiliary bridges
should be added. In this case, the nominal characteristic value should be modified accordingly.

• The reference and differential voltages are measured simultaneously.

• Since the two voltages are measured at the same time, there is basically no need for a high-precision
reference voltage with respect to the level.
The bridge supply and reference voltages are provided by the ELX3351 for the full bridge. A
connection of other, externally supplied circuits (e.g. an external bridge supply) is not permitted!

• The change of the quotient of the differential and reference voltages corresponds to the relative force
acting on the load cell.

• The quotient is converted into a weight and is output as process data.

• The data processing is subject to the following filtering procedures:

◦ software filter IIR/FIR (if activated)

• The ELX3351 has an automatic compensation/self-calibration function.

◦ Default state: self-calibration activated, execution every 3 minutes
◦ Errors in the analog input stages (temperature drift, long-term drift etc.) are checked by regular

automatic calibration, and compensated to bring the measurement within the permitted
tolerance range.

◦ The automatic function can be deactivated or activated in a controlled manner.

5.1.1 General notes

General notes

• The measuring ranges of both channels (supply voltage and bridge voltage) should always be used as
widely as possible in order to achieve a high measuring accuracy.
We recommended a load cell that has such a sensitivity (e.g. 2mV/V) that the largest possible bridge
voltage (ideally ±20mV) is generated.

Note the input voltages (see Technical data [}12]).

Fig.25: Max. input voltages

ELX3351 33Version: 1.3.1

Parameterization and programming

• Parallel operation of load cells is possible with the ELX3351. Please note:

◦ Load cells approved and calibrated by the load cell manufacturer for parallel operation should

be used. The nominal characteristic values [mV/V], zero offset [mV/V] and impedance [Ω, ohm]

are then usually adjusted accordingly.
◦ A 6-wire connection is expressly recommended.
◦ All the relevant operating parameters (e.g. the minimum bridge input resistance)

must be observed.

Fig.26: Parallel connection with ELX3351

◦ Load cell signals have a low amplitude and are occasionally very sensitive to electromagnetic

interference. Considering the typical system characteristics and taking into account the

technical possibilities, purposeful state-of-the-art EMC protective measures are to be taken.

If shielded cables are used, the installation measures and, if necessary, the Separation

distances in accordance with IEC60079-11 and IEC60079-25 must be taken into account.

Under high EMC interference loads, it can be helpful to remove the cable shield in front of the

terminal additionally with suitable shielding material.

ELX335134 Version: 1.3.1

Parameterization and programming

5.1.2 Block diagram

Fig.27: ELX3351 - Block diagramm

The ELX3351 processes the data in the following order

1. Hardware low-pass 3.6KHz

2. 2-channel simultaneous sampling by delta-sigma (ΔΣ) converter and internal prefiltration

3. Software filter (can be deactivated)

4. Calculating the weight

Measurement principle of delta-sigma (ΔΣ) converter

The measurement principle employed in the ELX3351, with real sampling in the MHz

Note

range, shifts aliasing effects into a very high frequency range, so that normally no such ef­fects are to be expected in the KHz range.

5.1.3 Software filter

The ELX3351 is equipped with a digital software filter which, depending on its settings, can adopt the
characteristics of a Finite Impulse Response filter (FIR filter), or an Infinite Impulse Response filter (IIR filter).
The filter is activated by default as 50Hz-FIR.

In the respective measuring mode the filter can be activated (0x8000:01 [}60], 0x8000:02 [}60]) and
parameterized (0x8000:11 [}60], 0x8000:12 [}60]) (the ELX3351 supports only mode 0).

• FIR 50/60Hz
The filter performs a notch filter function and determines the conversion time of the terminal. The
higher the filter frequency, the faster the conversion time. A 50Hz and a 60Hz filter are available.
Notch filter means that the filter has zeros (notches) in the frequency response at the filter frequency
and multiples thereof, i.e. it attenuates the amplitude at these frequencies. The FIR filter operates as a
non-recursive filter.

Fig.28: Notch characteristic/amplitude curve and step response of the FIR filter

ELX3351 35Version: 1.3.1

Parameterization and programming

• IIR-Filter 1 to 8
The filter with IIR characteristics is a discrete time, linear, time invariant filter that can be set to eight
levels (level 1 = weak recursive filter, up to level 8 = strong recursive filter).
The IIR can be understood to be a moving average value calculation after a low-pass filter.

Fig.29: Step response of the IIR filter

Filter and cycle time

If the FIR filters (50Hz or 60Hz) are switched on, the process data are updated maximally
with the specified conversion time. (see table) The IIR filter works cycle-synchronously.

Note

Hence, a new measured value is available in each PLC cycle.

IIR filter

Differential equation: Yn = Xn * a0 + Y

Note

with a0 + b1 = 1
a0 = (see table)
b1 = 1 - a

0

n-1

* b

1

ELX335136 Version: 1.3.1

Parameterization and programming

5.1.4 Dynamic filter

The dynamic IIR filter automatically switches through the 8 different IIR filters depending on the weight
change. The idea:

• The target state is always the IIR8-Filter, i.e. the greatest possible damping and hence a very calm
measured value.

• In the input variable changes rapidly the filter is opened, i.e. switched to the next lower filter (if still
possible). This gives the signal edge more weight and the measured value curve can follow the load
quickly.

• If the measured value changes very little the filter is closed, i.e. switched to the next higher filter (if still
possible). Hence the static state is mapped with a high accuracy.

• The evaluation as to whether a downward change of filter is required or whether an upward change is
possible takes place continuously at fixed time intervals.

Parameterization takes place via the CoE entries 0x8000:13 [}60] and 0x8000:14 [}60]. Evaluation takes
place according to 2 parameters:

• The "Dynamic filter change time" object (0x8000:13 [}60]) is used to set the time interval at which the
existing signal is re-evaluated.

• Object 0x8000:14 [}60] is used to specify the maximum deviation that is permissible during this time
without filter switching occurring.

Example:

The dynamic filter is to be adjusted in such a manner that a maximum slope of 0.5 digits per 100 ms (5 digits
per second) is possible without the filter being opened. This results in a "calm" measured value. In the case
of a faster change, however, it should be possible to immediately follow the load.

• Dynamic filter change time (0x8000:13 [}60]) = 10 (equivalent to 100 ms)

• Dynamic filter delta (0x8000:14 [}60]) = 0.5 (related to the calculated load value)

The measured value curve is shown below for a slower (left) and faster (right) change.

Fig.30: Effect of dynamic IIR filters

• Links: The scales are slowly loaded. The change in the weight (delta/time) remains below the mark of

0.5 digits per 100 ms. The filter therefore remains unchanged at the strongest level (IIR8), resulting in a
low-fluctuation measured value.

• Right: The scales are suddenly loaded. The change in the weight immediately exceeds the limit value
of 0.5 digits per 100 ms. The filter is opened every 100 ms by one level (IIR8 --> IIR7 --> IIR6 etc.) and
the display value immediately follows the jump. After the removal of the weight the signal quickly falls
again. If the change in the weight is less than 0.5 digit per 100 ms, the filter is set one level stronger
every 100 ms until IIR8 is reached. The green line is intended to clarify the decreasing "noise level"

ELX3351 37Version: 1.3.1

Parameterization and programming

5.1.5 Calculating the weight

Each measurement of the analog inputs is followed by the calculation of the resulting weight or the resulting
force, which is made up of the ratio of the measuring signal to the reference signal and of several
calibrations.

YR = (U
YL = ( (YR - CZB) / (Cn - CZB) ) * E
YS = Y
YG = Y
Y

AUS

/U

Diff

L * AS

S *

) x A

Ref

i

(G / 9.80665) (1.3) Influence of acceleration of gravity

(1.0) Calculation of the raw value in mV/V
(1.1) Calculation of the weight

max

(1.2) Scaling factor (e.g. factor 1000 for rescaling from kg to g)

= YGxGain - Tare (1.4) Gain and Tare

Name Description CoE Index

U
U
A

Bridge voltage/differential voltage of the sensor element, after filter

Diff

Bridge supply voltage/reference signal of the sensor element, after filter

Ref

Internal gain, not changeable. This factor accounts for the unit standardization

i

from mV to V and the different full-scale deflections of the input channels

C

Nominal characteristic value of the sensor element (unit mV/V, e.g. nominally

n

0x8000:23 [}60]

2mV/V or 2.0234 mV/V according to calibration protocol)

C

Zero balance of the sensor element (unit mV/V, e.g. -0.0142 according to

ZB

0x8000:25 [}60]

calibration protocol)

E
A
G Acceleration of gravity in m/s^2 (default: 9.80665 ms/s^2)
Gain
Tare

Nominal load of the sensor element

max

Scaling factor (e.g. factor 1000 for rescaling from kg to g)

S

0x8000:24 [}60]

0x8000:27 [}60]

0x8000:26 [}60]

0x8000:21 [}60]

0x8000:22 [}60]

5.2 Application notes

5.2.1 Wiring fail indication

The ELX3351 has no express open-circuit recognition facility. If one of the bridge wires is broken, however,
the voltage measured there generally moves towards the final value, thus displaying an error in the status
word. Over/underrange of the supply voltage is likewise indicated.

5.2.2 InputFreeze

If the terminal is placed in the freeze state by InputFreeze in the control word, no further analog measured
values are relayed to the internal filter. This function is usable, for example, if a filling surge is expected from
the application that would unnecessarily overdrive the filters due to the force load. This would result in a
certain amount of time elapsing until the filter had settled again. The user himself must determine a sensible
InputFreeze time for his filling procedure.

For clarification: temporal control of the InputFreeze and the decision regarding its use must be realized by
the user in the PLC, they are not components of the ELX3351.

In the following example (recorded with Scope2) impulses on a 15kg load cell are recorded; the filter is wide
open at IIR1 so that steep edges occur in the signal.

ELX335138 Version: 1.3.1

Parameterization and programming

Fig.31: InputFreeze example

Explanation: The weight (A) is shown in blue; the state of the InputFreeze variable, which can be controlled
by the PLC program and can be TRUE/FALSE, is shown in red (B). The first two impulses (C) lead to large
peak deflections in the signal. After that the following is activated in the PLC program (see example
program):

• if the measured value for the last cycle (cycle time 100µs) has changed by more than 10g (indicating
a sudden load),

• bInputFreeze is set to TRUE for 50ms by a TOF block on the ELX3351

The effect can be seen in (D): The peak load is no longer acknowledged by the ELX3351. If it is optimally
adapted to the expected force impulse, the ELX3351 can measure the current load value without overshoot.

5.2.3 Gravity adaptation

The calculation of the weight depends on the gravitation/the Earth's gravitational force/acceleration due to
gravity at the place of installation of the scales. In general, acceleration due to the gravitational pull of the
earth at the place of installation is not equal to the defined standard value of g = 9.80665m/s². For example,
4 zones of acceleration due to gravity are defined in Germany, in which a local acceleration due to gravity of

9.807 to 9.813 m/s² is to be assumed. Hence, within Germany alone there is a clear dispersion of the order
of parts per thousand for acceleration due to gravity, which has a direct effect on the measured weight in
accordance with the equation FG = m*g!

If

• load cells are used in the theoretical calibration with characteristic values according to the sensor
certificate

• calibration weights are used whose weight at the place of installation of the scales is by nature different
to that at the place of origin

• scales of the accuracy class I to III are to be realized

• scales that are generally independent of acceleration due to gravity are to be realized

ELX3351 39Version: 1.3.1

Parameterization and programming

then one should check whether the gravity correction needs to be adapted via object 0x8000:26 [}60].

5.2.4 Idling recognition

Weighing is a dynamic procedure that can lead to large jumps in the bridge voltage and thus to the
calculation of the value. Following a change in load, the measured value must first "settle" so that the
process value is evaluable in the controller. The evaluation of the measured value and the decision over the
degree of calmness can be done in the controller; however, the ELX3351 also offers this function, which is
activated by default. The result is output in the status word.

• If the load value remains within a range of values y for longer than time x, then the SteadyState is
activated in the StatusWord.

• SteadyState is set to FALSE as soon as this condition no longer applies.

• The parameters x and y can be specified in the CoE

• The evaluation is naturally considerably affected by the filter setting

In the following example (recorded with TwinCAT Scope2), a 15kg load cell is suddenly unloaded and
loaded with 547g. SteadyState is subject to a window time from 100ms and a tolerance of 8g (15kg
nominal value, scaling 1000; see CoE).

Fig.32: Idling recognition example

5.2.5 Official calibration capability

"Official calibration" is a special kind of calibration that is accomplished according to special regulations with
the involvement of trained personnel using prescribed aids. The use of "officially calibrated" scales is
mandatory in the Central European region, in particular for the filling of foodstuffs. This ensures the
correctness of the weighed quantities in a particular way.

The ELX3351 terminals cannot be officially calibrated as individual devices. However, they can be integrated
as elements in applications that can then be equipped by the integrator with the required characteristics for
official calibration capability using appropriate means.

5.3 Calibration and compensation

The term "calibration" can be applied in 3 different ways to the ELX3351:

• Sensor calibration: once-only calibration of the employed sensor (strain gauge) during commissioning
of the system

ELX335140 Version: 1.3.1

Parameterization and programming

• Self-calibration: continuously repeated self-calibration of the terminal for the improvement of the
measuring accuracy

• Tare: repeated gross/net compensation by taring

5.3.1 Sensor calibration

The ELX3351 is matched to the characteristic curve of the sensor element by means of the calibration. Two
values are required for this procedure: the initial value without a load (zero balance) and fully loaded (rated
output). These values can be determined by a calibration protocol or by a calibration using calibration
weights.

Fig.33: Adaptation to the sensor curve

Calibration by means of compensation in the system

In the practical calibration, measurement takes place first with the scales unloaded, then with a defined load
on the scales. The ELX3351 automatically calculates the existing sensor characteristic values from the
measured values.

Sequence:

1. Perform a CoE reset with object 0x1011:01
see Restoring the delivery state

2. Activate mode 0 via the control word

3. Set scale factor to 1 (0x8000:27 [}60])

4. Set gravity of earth (0x8000:26) [}60] if necessary (default: 9.806650)

5. Ste gain to (0x8000:21 [}60]) = 1

6. Set tare to 0 (0x8000:22 [}60])

7. Set the filter (0x8000:11 [}60]) to the strongest level: IIR8

8. Specify the nominal load of the sensor in 0x8000:24 [}60] ("Nominal load")

9. Zero balance: Do not load the scales
As soon as the measured value indicates a constant value for at least 10 seconds, execute the com­mand 0x0101 (257

) on CoE object 0xFB00:01.

dec

This command causes the current mV/V value(0x9000:11 [}62]) to be entered in the "Zero balance"
object.
Check: CoE objects FB00:02 and FB00:03 must contain "0" after execution

ELX3351 41Version: 1.3.1

Parameterization and programming

Fig.34: Zero calibration with command 0x0101 in CoE object 0xFB00:01

10. Load the scales with a reference load. This should be at least 20% of the rated load. The larger the
reference load, the better the sensor values can be calculated.

In object 0x8000:28 [}60] ("Reference load"), enter the load in the same unit as the rated load
(0x8000:24 [}60]).

As soon as the measured value indicates a constant value for at least 10 seconds, execute the com­mand "0x0102" (258

) on CoE object 0xFB00:01.

dec

By means of this command the ELX3351 determines the output value for the nominal weight ("Rated
output")
Check: CoE objects FB00:02 and FB00:03 must contain "0" after execution

Fig.35: Loading with reference load, command 0x0102 in CoE object 0xFB00:01

11. Reset: execute the command 0x0000 (0

) on CoE object 0xFB00:01.

dec

12. Set the filter to a lower stage.

Calibration according to the sensor calibration protocol (theoretical calibration)

The sensor characteristic values according to the manufacturer's certificate are communicated here directly
to the ELX3351, so that it can calculate the load.

1. Execute a CoE reset

2. Set scale factor to 1 (0x8000:27 [}60])

3. Set gravity of earth (0x8000:26) [}60] if necessary (default: 9.806650)

4. Ste gain to (0x8000:21 [}60]) = 1

5. Set tare to 0 (0x8000:22 [}60])

6. Specify the nominal load of the sensor in 0x8000:24 [}60] (Nominal load)

7. Adopt the "Rated output" (mV/V value 0x8000:23 [}60]) from the calibration protocol

8. Adopt the "Zero balance" (0x8000:25 [}60]) from the calibration protocol

ELX335142 Version: 1.3.1

Parameterization and programming

Calibration

The calibration is of great importance for the accuracy of the system. In order to increase

Note

this, the filter should be set as strong as possible over the entire calibration phase. It may
take several seconds before a static value is obtained.

Local storage

The values modified during the theoretical and practical calibration are stored in a local

Note

EEPROM. This can be written to up to 1 million time. In order to prolong the life of the EEP­ROM, therefore, the commands should not be executed cyclically.

5.3.2 Self-calibration

Self-calibration of the measuring amplifiers

The measuring amplifiers are periodically subjected to examination and self-calibration. Several analog
switches are provided for this purpose, so that the various calibration signals can be connected. It is
important for this process that the entire signal path, including all passive components, is examined at every
phase of the calibration. Only the interference suppression elements (L/C combination) and the analog
switches themselves cannot be examined. In addition, a self-test is carried out at longer intervals.

The self-calibration is carried out every 3 minutes in the default setting.

• Self-calibration
The time interval is set in 100ms steps with object 0x8000:31 [}60]; default: 3min.

Duration approx. 150ms

By means of the self-calibration of the input stages at the two operating points (zero point and final value),
the two measuring channels are calibrated to each other.

Interface for controller

The self-calibration takes place automatically at the defined intervals. In order to prevent calibration during a
time-critical measurement, the automatic calibration can be disabled permanently via the Disable calibration
bit in ControlWord. If it should be additional necessary to carry out a manual test, this is started by a rising
edge of the Start manual calibration bit in the process image.

While the terminal is performing a self-calibration, the Calibration in progress bit is set in the process image.
Once started, a self-calibration cannot be aborted.

If the self-calibration has been disabled by Disable calibration, it can nevertheless be started by the Start
calibration process data bit.

Self-calibration

The self-calibration takes place for the first time directly after starting up the terminal. At this

Note

point the supply voltage must already be applied. If the supply voltage is only applied later,
the self-calibration must be manually initiated (process data bit: Start calibration).
The self-calibration must be executed at least once after each start-up.

A lower measuring accuracy is expected if the self-calibration is disabled for a longer period
or permanently.

After a change in the CoE settings (section x80nn), a self-calibration is always performed (even if
DisabledCalibration = TRUE), since the settings affect the measurement. Changing the CoE settings during
an ongoing measurement should therefore be avoided, if possible.

ELX3351 43Version: 1.3.1

Parameterization and programming

5.3.3 Taring

When taring, the scales are zeroed using an arbitrary applied load; i.e. an offset correction is performed. This
is necessary for the gross/net compensation of goods that cannot be weighed without a container that has a
mass of its own.

The ELX3351 supports 2 tarings; it is recommended to set a strong filter when taring.

• Temporary tare
The correction value is NOT stored in the terminal and is lost in the event of a power failure.
To this end the command 0x0001 is executed on CoE object 0xFB00:01 (binary dialog in the System

Manager: 01 00). This sets the tare object (0x8000:22 [}60]) such that the display value is 0.
Note: in the case of a device restart (INIT->OP) the tare is not deleted.
In addition this tare can be executed via the control word:

Fig.36: Control word, tare

• Permanent tare
The correction value is stored locally in the terminal's EEPROM and is not lost in the event of a power
failure.
To this end the command 0x0002 is executed on CoE object 0xFB00:01 (binary dialog in the System

Manager: 02 00). This sets the tare object (0x8000:22 [}60]) such that the display value is 0.

Local storage

The values modified during the theoretical and practical calibration are stored in a local

Note

EEPROM. This can be written to up to 1 million time. In order to prolong the life of the EEP­ROM, therefore, the commands should not be executed cyclically.

5.3.4 Overview of commands

The functions described above are carried out by means of commands in the standardized object 0xFB00.

Index Name Comment

FB00:01 Request Entry of the command to be executed
FB00:02 Status Status of the command currently being executed

0: Command executed without error.
255: Command is being executed

FB00:03 Response Optional response value of the command

The function blocks FB_EcCoESdoWrite and FB_EcCoESdoRead from the TcEtherCAT.lib (contained in the
standard TwinCAT installation) can be used in order to execute the commands from the PLC.

Commands of the ELX3351

The following commands can be transferred to the terminal via the CoE entry 0xFB00:01.

Command Comment

0x0101 Execute zero balance
0x0102 Execute calibration
0x0001 Execute tare procedure (value is NOT saved in the terminal's EEprom)
0x0002 Execute tare procedure (value is saved in the terminal's EEprom)

ELX335144 Version: 1.3.1

Parameterization and programming

5.4 Notices on analog specifications

Beckhoff I/O devices (terminals, boxes, modules) with analog inputs are characterized by a number of
technical characteristic data; refer to the technical data in the respective documents.

Some explanations are given below for the correct interpretation of these characteristic data.

5.4.1 Full scale value (FSV)

An I/O device with an analog input measures over a nominal measuring range that is limited by an upper and
a lower limit (initial value and end value); these can usually be taken from the device designation.
The range between the two limits is called the measuring span and corresponds to the equation (end value ­initial value). Analogous to pointing devices this is the measuring scale (see IEC61131) or also the dynamic
range.

For analog I/O devices from Beckhoff the rule is that the limit with the largest value is chosen as the full scale
value of the respective product (also called the reference value) and is given a positive sign. This applies to
both symmetrical and asymmetrical measuring spans.

Fig.37: Full scale value, measuring span

For the above examples this means:

• Measuring range 0...10V: asymmetric unipolar, full scale value=10V, measuring span=10V

• Measuring range 4...20 mA: asymmetric unipolar, full scale value = 20mA, measuring span=16mA

• Measuring range -200...1370°C: asymmetric bipolar, full scale value=1370°C, measuring
span=1570°C

• Measuring range -10...+10V: symmetric bipolar, full scale value = 10V, measuring span=20V

This applies to analog output terminals/ boxes (and related Beckhoff product groups).

5.4.2 Measuring error/ measurement deviation

The relative measuring error (% of the full scale value) is referenced to the full scale value and is calculated
as the quotient of the largest numerical deviation from the true value (‘measuring error’) referenced to the full
scale value.

The measuring error is generally valid for the entire permitted operating temperature range, also called the
‘usage error limit’ and contains random and systematic portions of the referred device (i.e. ‘all’ influences
such as temperature, inherent noise, aging, etc.).

It is always to be regarded as a positive/negative span with ±, even if it is specified without ± in some cases.

ELX3351 45Version: 1.3.1

Parameterization and programming

The maximum deviation can also be specified directly.

Example: Measuring range 0...10V and measuring error <±0.3% full scale value → maximum deviation ±
30mV in the permissible operating temperature range.

Lower measuring error

Since this specification also includes the temperature drift, a significantly lower measuring
error can usually be assumed in case of a constant ambient temperature of the device and

Note

thermal stabilization after a user calibration.
This applies to analog output devices.

5.4.3 Temperature coefficient tK [ppm/K]

An electronic circuit is usually temperature dependent to a greater or lesser degree. In analog measurement
technology this means that when a measured value is determined by means of an electronic circuit, its
deviation from the "true" value is reproducibly dependent on the ambient/operating temperature.

A manufacturer can alleviate this by using components of a higher quality or by software means.

The temperature coefficient, when indicated, specified by Beckhoff allows the user to calculate the expected
measuring error outside the basic accuracy at 23 °C.

Due to the extensive uncertainty considerations that are incorporated in the determination of the basic
accuracy (at 23 °C), Beckhoff recommends a quadratic summation.

Example: Let the basic accuracy at 23 °C be ±0.01% typ. (full scale value), tK = 20 ppm/K typ.; the accuracy
A35 at 35 °C is wanted, hence ΔT = 12 K

Remarks: ppm ≙ 10

-6

% ≙ 10

-2

ELX335146 Version: 1.3.1

Parameterization and programming

5.4.4 Single-ended/differential typification

For analog inputs Beckhoff makes a basic distinction between two types: single-ended (SE) and differential
(DIFF), referring to the difference in electrical connection with regard to the potential difference.

The diagram shows two-channel versions of an SE module and a DIFF module as examples for all multi­channel versions.

Fig.38: SE and DIFF module as 2-channel version

Note: Dashed lines indicate that the respective connection may not necessarily be present in each SE or
DIFF module. Electrical isolated channels are operating as differential type in general, hence there is no
direct relation (voltaic) to ground within the module established at all. Indeed, specified information to
recommended and maximum voltage levels have to be taken into account.

The basic rule:

• Analog measurements always take the form of voltage measurements between two potential points.
For voltage measurements a large R is used, in order to ensure a high impedance. For current
measurements a small R is used as shunt. If the purpose is resistance measurement, corresponding
considerations are applied.

◦ Beckhoff generally refers to these two points as input+/signal potential and input-/reference

potential.
◦ For measurements between two potential points two potentials have to be supplied.
◦ Regarding the terms "single-wire connection" or "three-wire connection", please note the

following for pure analog measurements: three- or four-wire connections can be used for

sensor supply, but are not involved in the actual analog measurement, which always takes

place between two potentials/wires.

In particular this also applies to SE, even though the term suggest that only one wire is

required.

• The term "electrical isolation" should be clarified in advance.
Beckhoff IO modules feature 1..8 or more analog channels; with regard to the channel connection a
distinction is made in terms of:

◦ how the channels WITHIN a module relate to each other, or
◦ how the channels of SEVERAL modules relate to each other.

ELX3351 47Version: 1.3.1

Parameterization and programming

The property of electrical isolation indicates whether the channels are directly connected to each
other.

◦ Beckhoff terminals/ boxes (and related product groups) always feature electrical isolation

between the field/analog side and the bus/EtherCAT side. In other words, if two analog
terminals/ boxes are not connected via the power contacts (cable), the modules are effectively
electrically isolated.

◦ If channels within a module are electrically isolated, or if a single-channel module has no

power contacts, the channels are effectively always differential. See also explanatory notes
below. Differential channels are not necessarily electrically isolated.

• Analog measuring channels are subject to technical limits, both in terms of the recommended operating
range (continuous operation) and the destruction limit. Please refer to the respective terminal/ box
documentation for further details.

Explanation

• differential (DIFF)

◦ Differential measurement is the most flexible concept. The user can freely choose both

connection points, input+/signal potential and input-/reference potential, within the framework
of the technical specification.

◦ A differential channel can also be operated as SE, if the reference potential of several sensors

is linked. This interconnection may take place via the system GND.

◦ Since a differential channel is configured symmetrically internally (cf. Fig. SE and DIFF module

as 2-channel variant), there will be a mid-potential (X) between the two supplied potentials that
is the same as the internal ground/reference ground for this channel. If several DIFF channels
are used in a module without electrical isolation, the technical property VCM (common-mode
voltage) indicates the degree to which the mean voltage of the channels may differ.

◦ The internal reference ground may be accessible as connection point at the terminal/ box, in

order to stabilize a defined GND potential in the terminal/ box. In this case it is particularly
important to pay attention to the quality of this potential (noiselessness, voltage stability). At
this GND point a wire may be connected to make sure that V

is not exceeded in the

CM,max

differential sensor cable.
If differential channels are not electrically isolated, usually only one V

is permitted. If the

CM, max

channels are electrically isolated this limit should not apply, and the channels voltages may
differ up to the specified separation limit.

◦ Differential measurement in combination with correct sensor wiring has the special advantage

that any interference affecting the sensor cable (ideally the feed and return line are arranged
side by side, so that interference signals have the same effect on both wires) has very little
effect on the measurement, since the potential of both lines varies jointly (hence the term
common mode). In simple terms: Common-mode interference has the same effect on both
wires in terms of amplitude and phasing.

◦ Nevertheless, the suppression of common-mode interference within a channel or between

channels is subject to technical limits, which are specified in the technical data.

◦ Further helpfully information on this topic can be found on the documentation page

Configuration of 0/4..20mA differential inputs (see documentation for the EL30xx terminals, for
example).

• Single Ended (SE)

◦ If the analog circuit is designed as SE, the input/reference wire is internally fixed to a certain

potential that cannot be changed. This potential must be accessible from outside on at least
one point for connecting the reference potential, e.g. via the power contacts (cable).

◦ In other words, in situations with several channels SE offers users the option to avoid returning

at least one of the two sensor cables to the terminal/ box (in contrast to DIFF). Instead, the
reference wire can be consolidated at the sensors, e.g. in the system GND.

◦ A disadvantage of this approach is that the separate feed and return line can result in voltage/

current variations, which a SE channel may no longer be able to handle. See common-mode
interference. A VCM effect cannot occur, since the module channels are internally always 'hard­wired' through the input/reference potential.

ELX335148 Version: 1.3.1

Parameterization and programming

Typification of the 2/3/4-wire connection of current sensors

Current transducers/sensors/field devices (referred to in the following simply as ‘sensor’) with the industrial
0/4-20 mA interface typically have internal transformation electronics for the physical measured variable
(temperature, current, etc.) at the current control output. These internal electronics must be supplied with
energy (voltage, current). The type of cable for this supply thus separates the sensors into self-supplied or
externally supplied sensors:

Self-supplied sensors

• The sensor draws the energy for its own operation via the sensor/signal cable + and -.
So that enough energy is always available for the sensor’s own operation and open-circuit detection is
possible, a lower limit of 4 mA has been specified for the 4-20 mA interface; i.e. the sensor allows a
minimum current of 4 mA and a maximum current of 20 mA to pass.

• 2-wire connection see Fig. 2-wire connection, cf. IEC60381-1

• Such current transducers generally represent a current sink and thus like to sit between + and – as a
‘variable load’. Refer also to the sensor manufacturer’s information.

Fig.39: 2-wire connection

Therefore, they are to be connected according to the Beckhoff terminology as follows:

preferably to ‘single-ended’ inputs if the +Supply connections of the terminal/ box are also to be used ­connect to +Supply and Signal

they can, however, also be connected to ‘differential’ inputs, if the termination to GND is then
manufactured on the application side – to be connected with the right polarity to +Signal and –Signal
It is important to refer to the information page Configuration of 0/4..20mA differential inputs (see
documentation for the EL30xx terminals, for example)!

Externally supplied sensors

An external supply of sensors / actuators, which are connected to signal ter­minals of the ELX series is not permitted!

WARNING

In terms of intrinsic safety, all signal terminals of the ELX series are energy-supplying, as­sociated equipment. For this reason, connected sensors or actuators are supplied exclu­sively via the respective channel of the terminal and must not be externally supplied in any
form (e.g. via an additional, external supply voltage).

This limitation is also independent of whether the additional, external supply is energy lim­ited in the sense of IEC60079-11.

Connecting any externally powered, intrinsically safe circuits to a ELX signal terminal con­tradicts the intended use and the specified technical data for explosion protection [}13].

The explosion protection provided by the specified type of protection thus automatically ex­pires.

ELX3351 49Version: 1.3.1

Parameterization and programming

5.4.5 Common-mode voltage and reference ground (based on differential inputs)

Common-mode voltage (Vcm) is defined as the average value of the voltages of the individual connections/
inputs and is measured/specified against reference ground.

Fig.40: Common-mode voltage (Vcm)

The definition of the reference ground is important for the definition of the permitted common-mode voltage
range and for measurement of the common-mode rejection ratio (CMRR) for differential inputs.

The reference ground is also the potential against which the input resistance and the input impedance for
single-ended inputs or the common-mode resistance and the common-mode impedance for differential
inputs is measured.

The reference ground is usually accessible at or near the terminal/ box, e.g. at the terminal contacts, power
contacts (cable) or a mounting rail. Please refer to the documentation regarding positioning. The reference
ground should be specified for the device under consideration.

For multi-channel terminals/ boxes with resistive (=direct, ohmic, galvanic) or capacitive connection between
the channels, the reference ground should preferably be the symmetry point of all channels, taking into
account the connection resistances.

Reference ground samples for Beckhoff IO devices:

1. Internal AGND fed out: EL3102/EL3112, resistive connection between the channels

2. 0V power contact: EL3104/EL3114, resistive connection between the channels and AGND; AGND
connected to 0V power contact with low-resistance

3. Earth or SGND (shield GND):

◦ EL3174-0002: Channels have no resistive connection between each other, although they are

capacitively coupled to SGND via leakage capacitors

◦ EL3314: No internal ground fed out to the terminal points, although capacitive coupling to

SGND

5.4.6 Dielectric strength

A distinction should be made between:

• Dielectric strength (destruction limit): Exceedance can result in irreversible changes to the electronics
◦ Against a specified reference ground
◦ Differential

• Recommended operating voltage range: If the range is exceeded, it can no longer be assumed that the

system operates as specified

◦ Against a specified reference ground
◦ Differential

ELX335150 Version: 1.3.1

Parameterization and programming

Fig.41: Recommended operating voltage range

The device documentation may contain particular specifications and timings, taking into account:

• Self-heating

• Rated voltage

• Insulating strength

• Edge steepness of the applied voltage or holding periods

• Normative environment (e.g. PELV)

5.4.7 Temporal aspects of analog/digital conversion

The conversion of the constant electrical input signal to a value-discrete digital and machine-readable form
takes place in the analog Beckhoff EL/KL/EP input modules with ADC (analog digital converter). Although
different ADC technologies are in use, from a user perspective they all have a common characteristic: after
the conversion a certain digital value is available in the controller for further processing. This digital value,
the so-called analog process data, has a fixed temporal relationship with the “original parameter”, i.e. the
electrical input value. Therefore, corresponding temporal characteristic data can be determined and specified
for Beckhoff analogue input devices.

This process involves several functional components, which act more or less strongly in every AI (analog
input) module:

• the electrical input circuit

• the analog/digital conversion

• the digital further processing

• the final provision of the process and diagnostic data for collection at the fieldbus (EtherCAT, K‑bus,

etc.)

Fig.42: Signal processing analog input

Two aspects are crucial from a user perspective:

ELX3351 51Version: 1.3.1

Parameterization and programming

• “How often do I receive new values?”, i.e. a sampling rate in terms of speed with regard to the device/

channel

• What delay does the (whole) AD conversion of the device/channel cause?

- i.e. the hardware and firmware components in its entirety. For technological reasons, the signal
characteristics must be taken into account when determining this information: the run times through the
system differ, depending on the signal frequency.

This is the “external” view of the “Beckhoff AI channel” system – internally the signal delay in particular is
composed of different components: hardware, amplifier, conversion itself, data transport and processing.
Internally a higher sampling rate may be used (e.g. in the deltaSigma converters) than is offered “externally”
from the user perspective. From a user perspective of the “BeckhoffAIchannel” component this is usually
irrelevant or is specified accordingly, if it is relevant for the function.

For Beckhoff AI devices the following specification parameters for the AI channel are available for the user
from a temporal perspective:

1. Minimum conversion time [ms, µs]

= the reciprocal value of the maximum sampling rate [sps, samples per second]:
Indicates how often the analog channel makes a newly detected process data value available for collection
by the fieldbus. Whether the fieldbus (EtherCAT, K-bus) fetches the value with the same speed (i.e.
synchronous), or more quickly (if the AI channel operates in slow FreeRun mode) or more slowly (e.g. with
oversampling), is then a question of the fieldbus setting and which modes the AI device supports.
For EtherCAT devices the so-called toggle bit indicates (by toggling) for the diagnostic PDOs when a newly
determined analog value is available.
Accordingly, a maximum conversion time, i.e. a smallest sampling rate supported by the AI device, can be
specified.
Corresponds to IEC 61131-2, section 7.10.2 2, “Sampling repeat time”

2. Typical signal delay
Corresponds to IEC 61131-2, section 7.10.2 1, “Sampling duration”. From this perspective it includes all
internal hardware and firmware components, but not “external” delay components from the fieldbus or the
controller (TwinCAT).
This delay is particularly relevant for absolute time considerations, if AI channels also provide a time stamp
that corresponds to the amplitude value – which can be assumed to match the physically prevailing
amplitude value at the time.
Due to the frequency-dependent signal delay time, a dedicated value can only be specified for a given
signal. The value also depends on potentially variable filter settings of the channel.
A typical characterization in the device documentation may be:

2.1Signal delay (step response)

Keywords: Settling time
The square wave signal can be generated externally with a frequency generator (note impedance!)
The 90% limit is used as detection threshold.
The signal delay [ms, µs] is then the time interval between the (ideal) electrical square wave signal and the
time at which the analog process value has reached the 90% amplitude.

ELX335152 Version: 1.3.1

Parameterization and programming

Fig.43: Diagram signal delay (step response)

2.2Signal delay (linear)

Keyword: Group delay
Describes the delay of a signal with constant frequency
A test signal can be generated externally with a frequency generator, e.g. as sawtooth or sine. A
simultaneous square wave signal would be used as reference.
The signal delay [ms, µs] is then the interval between the applied electrical signal with a particular amplitude
and the moment at which the analog process value reaches the same value.
A meaningful range must be selected for the test frequency, e.g. 1/20 of the maximum sampling rate.

Fig.44: Diagram signal delay (linear)

3. Additional information:
may be provided in the specification, e.g.

3.1Actual sampling rate of the ADC (if different from the channel sampling rate)

3.2Time correction values for run times with different filter settings
…

ELX3351 53Version: 1.3.1

Parameterization and programming

5.5 Process data

This section describes the individual PDOs and their content. A PDO (Process Data Object) is a unit on
cyclically transmitted process values. Such a unit can be an individual variable (e.g. the weight as a 32-bit
value) or a group/structure of variables. The individual PDOs can be activated or deactivated separately in
the TwinCAT System Manager. The ‘Process data’ tab is used for this (visible only if the terminal is selected
on the left). A change in the composition of the process data in the TwinCAT System Manager becomes
effective only after restarting the EtherCAT system.

5.5.1 Selection of process data

The process data of the ELX3351 are set up in the TwinCAT System Manager. The PDOs can be activated
or deactivated separately. The ‘Process data’ tab is used for this (visible only if the terminal is selected on
the left).

Fig.45: ELX3351 – process data selection in the TwinCAT System Manager

If the terminal is selected in the System Manager (A), the Process data tab (B) shows the PDO selection.
The two SyncManagers of the inputs (SM3) and outputs (SM2) can be changed (C). If one of the two is
clicked on, the PDO possible for this SyncManager appears underneath it (D). PDOs that are already
activated have an activated checkbox in front of them; this is activated by clicking on it.

ELX335154 Version: 1.3.1

Parameterization and programming

The process data which then belong to the device are listed underneath it (G). So that the individual bit
meanings are visible, e.g. in the Status status word, and can be separately linked (G), ShowSubVariables
must be activated in the System Manager (F). The bit position at which the subvariables are located in the
status or control word Ctrl) can be taken from the address overview (H) or the following information.

Predefined PDO Assignment

In order to simplify the configuration, typical configuration combinations of process data are stored in the
device description. The predefined configurations can be selected in the process data overview. Therefore

the function is available only if the ESI/XML files are saved in the system (downloadable from the Beckhoff
website).

The following combinations are possible (see also Fig. ELX3351 process data selection in the TwinCAT
System Manager, E):

Fig.46: ELX3351 - selection Predefined PDO Assignment

• Standard (INT32): [Default setting] load calculation; 32-bit integer load value as final value according to

the calculation specifications in the CoE, no further conversion necessary in the PLC.

• Standard (REAL): Load calculation; 32-bit floating-point load value as final value according to the

calculation specifications in the CoE, no further conversion necessary in the PLC.

5.5.2 Default process image

The default process image is standard (INT32).

ELX3351 55Version: 1.3.1

Parameterization and programming

Fig.47: ELX3351 - Default process image

Note regarding ELX3351: No switching of SampleMode in the Ctrl word

Function of the variables

Variable Meaning

Status The status word (SW) is located in the input process image, and is transmitted from terminal to the controller. For expla-

nation see the entries in the object overview, index 0x6000 [}61] see "Bit - meaning of the status word [}57]"
Value calculated 32-bit DINT load value in unit [1], with sign
Value (Real) calculated 32-bit floating point REAL load value with mantissa and exponent in unit [1]

The format matches the REAL format of IEC 61131-3, which in turn is based on the REAL format of IEC 559. A REAL

number (single precision) is defined as follows (See also Beckhoff InfoSys: TwinCAT PLC Control: standard data types).

According to IEC 61131, this 32-bit variable can be linked directly with a FLOAT variable of the PLC, see "Bit - meaning

of the variable value (REAL) [}57]"
WcState cyclic diagnostic variable; "0" indicates correct data transmission
Status State of the EtherCAT device; State.3 = TRUE indicates correct operation in OP
AdsAddr AmsNet address of the EtherCAT device from AmsNetId (in this case: 192.168.0.20.5.1) and port (in this case: 1003)
Ctrl The control word (CW) is located in the output process image, and is transmitted from the controller to the terminal. For

explanation see the entries in the object overview, index 0x7000 [}61] see "Bit - meaning of the control word [}57]"

See also the example program for the dissection of the Status and CTRL variable.

ELX335156 Version: 1.3.1

Parameterization and programming

Bit - meaning of the Status Word

Bit SW.15 SW.14 SW.13 SW.12 -

Name TxPDO Tog-

gle

Meaning toggeles

0->1->0 with
each up­dated data
set

- - - Steady State Calibra-

- - - Idling recogni-

SW.9

SW.8 SW.7 SW.6 SW.5 -

Error - Data invalid - Over -

Collective
error dis­play

tion

tion in
progress

Calibra­tion in
progress

SW.4

- Input data

SW.3 SW.2SW.1 SW.

range

are invalid

- Measuring
range ex­ceeded

Bit - purpose of the variable Value (Real)

Bit position (from left) 1 8 23 (+1 "hidden bit", see IE559)
Function Sign Exponent Mantissa

Bit - meaning of the Control Word

Bit CW.15 -

CW.5

Name - Tare - Input Freeze Disable Calibration Start Calibration
Meaning - starts tare - stops the measurement switches the automatic self-cali-

CW.4 CW.3 CW.2 CW.1 CW.0

bration off

starts the self-calibra­tion immediately

0

-

-

5.5.3 Variants Predefined PDO

Floating-point representation of the load

The display of the load value can also be converted already in the terminal into a point representation. To do
this the input PDOs are to be changed as follows:

Fig.48: Load value in floating-point representation

Variable Meaning

Value
(Real)

calculated 32-bit floating point REAL load value with mantissa and exponent in unit [1]
The format matches the REAL format of IEC 61131-3, which in turn is based on the REAL format

of IEC 559. A REAL number (single precision) is defined as follows (See also Beckhoff InfoSys:
TwinCAT PLC Control: standard data types). According to IEC61131, this 32-bit variable can be

linked directly with a FLOAT variable of the PLC, see "Bit – meaning of the variable value
(REAL)"

ELX3351 57Version: 1.3.1

Parameterization and programming

5.5.4 Sync Manager

PDO Assignment

Inputs: SM3, PDO Assignment 0x1C13

Index Index of ex-

0x1A00
(default)

0x1A01(d
efault)

0x1A02 0x1A01

cluded PDOs

- 2.0 RMB Status

0x1A02
0x1A04
0x1A05
0x1A06
0x1A07

0x1A04
0x1A05
0x1A06
0x1A07

Size
(byte.bit)

4.0 RMB Value (INT32)

4.0 RMB Value (Real)

Name PDO content

(Resistor Measurement
Bridge)

Index 0x6000:02 [}61] - Overrange
Index 0x6000:04 [}61] - Data invalid
Index 0x6000:07 [}61] - Error
Index 0x6000:08 [}61] - Calibration in progress
Index 0x6000:09 [}61] - Steady State
Index 0x6000:10 [}61] - TxPDO Toggle

Index 0x6000:11 [}61] - Value

Index 0x6000:12 [}61] - Value (Real)

Outputs: SM2, PDO assignment 0x1C12

Index Index of ex-

0x1600
(default)

cluded PDOs

- 2.0 RMB Control

Size
(byte.bit)

Name PDO content

(Resistor Measurement
bridge)

Index 0x7000:01 [}61] - Start calibration
Index 0x7000:02 [}61] - Disable calibration
Index 0x7000:03 [}61] - Input freeze
Index 0x7000:05 [}61] - Tare

ELX335158 Version: 1.3.1

Parameterization and programming

5.6 ELX3351 - Object description and parameterization

EtherCAT XML Device Description

The display matches that of the CoE objects from the EtherCAT XML Device Description.

Note

Note

5.6.1 Restore object

Index 1011 Restore default parameters

Index Name Meaning Data type Flags Default

1011:0 Restore default param-

1011:01 SubIndex 001 If this object is set to “0x64616F6C” in the set value di-

We recommend downloading the latest XML file from the download area of the Beckhoff
website and installing it according to installation instructions.

Parameterization via the CoE list (CAN over EtherCAT)

The EtherCAT device is parameterized via the CoE-Online tab (double-click on the respec­tive object) or via the Process Data tab (allocation of PDOs). Please note the following gen­eral CoE notes when using/manipulating the CoE parameters:

• Keep a startup list if components have to be replaced

• Differentiation between online/offline dictionary, existence of current XML description

• use “CoE reload” for resetting changes

eters

Restore default parameters UINT8 RO 0x01 (1

alog, all backup objects are reset to their delivery state.

UINT32 RW 0x00000000

(0

)

dec

)

dec

ELX3351 59Version: 1.3.1

Parameterization and programming

5.6.2 Configuration data

Index 8000 RMB Settings

Index (hex) Name Meaning Data type Flags Default

8000:0 RMB Settings Max. subindex UINT8 RO 0x32 (50
8000:01 Enable filter 0: No filters active. The terminal operates cycle-syn-

BOOLEAN RW 0x01 (1

chronous
1: The filter settings selected in subindex 0x8000:11

or 0x8000:12 are active.
8000:03 Enable averager Activate hardware mean value filter BOOLEAN RW 0x01 (1
8000:05 Symmetric reference

Activate symmetric measurement BOOLEAN RW 0x01 (1

potential

8000:11 Mode0 filter settings 0: FIR 50 Hz

UINT16 RW 0x0000 (0
1: FIR 60 Hz
2: IIR 1
3: IIR 2
4: IIR 3
5: IIR 4
6: IIR 5
7: IIR 6
8: IIR 7
9: IIR 8
10: Dynamic IIR

8000:13 Dynamic filter change

time

Sampling rate for dynamic filter switching.
Scaling in 0.01ms (100 = 1s)

UINT16 RW 0x000A (10

(only if the filters are active and "dynamic IIR" is se­lected as filter)

8000:14 Dynamic filter delta Limit value for dynamic filter switching.

(only if the filters are active and "dynamic IIR" is se­lected as filter)

REAL32 RW 0x41A00000

(1101004800

20.0

8000:21 Gain Scale factor REAL32 RW 0x3F800000

(1065353216

1.0

8000:22 Tare Process data value offset REAL32 RW 0x00000000 (0

0.0

8000:23 Rated output Nominal characteristic value of the sensor element in

mV/V

REAL32 RW 0x40000000

(1073741824

2.0

8000:24 Nominal load Nominal load of the force transducer/load cell/etc.

(e.g. in kg, N or ...)

REAL32 RW 0x40A00000

(1084227584

5.0

8000:25 Zero balance Zero point offset in mV/V REAL32 RW 0x00000000 (0

0.0

8000:26 Gravity of earth Current acceleration of gravity (default 9.806650) REAL32 RW 0x411CE80A

(1092413450

9.806650

8000:27 Scale factor This factor can be used to re-scale the process data.

In order to change the display from kg to g, for exam­ple, the factor 1000 can be entered here.

REAL32 RW 0x447A0000

(1148846080

1000.0

8000:28 Reference load Reference weight for manual calibration REAL32 RW 0x40A00000

(1084227584

5.0

8000:29 Steady state window Time constant for the "steady state" bit (used for idle

UINT16 RW 0x03E8 (1000
recognition)

8000:2A Steady state toler-

Tolerance window for the "steady state" bit UINT32 RW 0x00000005 (5

ance

8000:31 Calibration interval Calibration interval for automatic calibration of the

UINT16 RW 0x0708 (1800
terminal.

The unit is 100ms.
The smallest possible value is 5 (500ms). A value of

0 deactivates automatic self-calibration. This is also
possible via the process data bit "Disable calibration".

)

dec

)

dec

)

dec

)

dec

dec

dec

)

)

) =

dec

) =

dec

) =

dec

) =

dec

) =

dec

) =

dec

) =

dec

) =

dec

) =

dec

)

dec

)

dec

)

dec

ELX335160 Version: 1.3.1

Parameterization and programming

5.6.3 Command object

Index FB00 RMB Command

Index (hex) Name Meaning Data type Flags Default

FB00:0 RMB Command Max. subindex UINT8 RO 0x03 (3
FB00:01 Request Commands can be sent to the terminal via the re-

quest object. Command:

• 0x0101: Zero balance

• 0x0102: Calibration

• 0x0001 Taring

• 0x0002 Taring (data are stored in the
EEPROM)

see commands

FB00:02 Status Status of the command currently being executed

0: Command executed without error.
255: Command is being executed

FB00:03 Response Optional response value of the command OCTET-

OCTET-

RW {0}

STRING[2]

UINT8 RO 0x00 (0

RO {0}

STRING[4]

)

dec

)

dec

5.6.4 Input data

Index 6000 RMB Inputs

Index (hex) Name Meaning Data type Flags Default

6000:0 RMB Inputs Max. Subindex UINT8 RO 0x13 (19
6000:02 Overrange The measured value has reached its end value BOOLEAN RO 0x00 (0
6000:04 Data invalid The displayed process data are invalid. e.g. during

BOOLEAN RO 0x00 (0

calibration.
6000:07 Error An error has occurred. BOOLEAN RO 0x00 (0
6000:08 Calibration in

progress

Calibration is running. The process data show the

last valid measured value.

BOOLEAN RO 0x00 (0

6000:09 Steady state BOOLEAN RO 0x00 (0
6000:10 TxPDO Toggle The TxPDO toggle is toggled by the slave when the

BOOLEAN RO 0x00 (0

data of the associated TxPDO is updated.
6000:11 Value Measured value as 32bit signed integer INT32 RO 0x61746144

(1635017028

6000:12 Value (Real) Measured value as real REAL32 RO 0x00000000 (0

)

dec

)

dec

)

dec

)

dec

)

dec

)

dec

)

dec

5.6.5 Output data

Index 7000 RMB Outputs

Index (hex) Name Meaning Data type Flags Default

7000:0 RMB Outputs Max. subindex UINT8 RO 0x05 (5
7000:01 Start calibration The calibration can be started manually with a rising

BOOLEAN RO 0x00 (0
edge. This can be used to prevent the calibration
from starting automatically at an unsuitable time.

7000:02 Disable calibration 0: Automatic calibration is active.

BOOLEAN RO 0x00 (0
1: Automatic calibration is switched off.

7000:03 Input freeze The process data and the digital filters are frozen. BOOLEAN RO 0x00 (0
7000:05 Tare The process record can be set to 0 with a rising

BOOLEAN RO 0x00 (0
edge. The tare value is not stored in the EEPROM
and is therefore no longer available after a terminal
reset.

)

dec

)

dec

)

dec

)

dec

)

dec

)

dec

)

dec

ELX3351 61Version: 1.3.1

Parameterization and programming

5.6.6 Information / diagnostic data

Index 9000 RMB Info data

Index (hex) Name Meaning Data type Flags Default

9000:0 RMB Info data Max. subindex UINT8 RO 0x11 (17
9000:11 mV/V Current mV/V value REAL32 RO 0x00000000 (0

Index A000 RMB Diag data

Index (hex) Name Meaning Data type Flags Default

A000:13 No external reference

supply
A000:15 Overrange bridge Measuring range exceeded in the bridge junction BOOLEAN RO 0x00 (0
A000:16 Underrange bridge Value below measuring range in the bridge junction BOOLEAN RO 0x00 (0
A000:17 Overrange supply Measuring range of the reference voltage exceeded BOOLEAN RO 0x00 (0
A000:18 Underrange supply Value below measuring range for the reference volt-

A000:21 ADC raw value supply ADC raw value bridge supply voltage INT32 RO 0x00 (0
A000:22 ADC raw value bridge ADC raw value bridge voltage INT32 RO 0x00 (0

The external reference voltage is less than ±1 V. BOOLEAN RO 0x00 (0

BOOLEAN RO 0x00 (0

age

)

dec

)

dec

)

dec

)

dec

)

dec

)

dec

)

dec

)

dec

)

dec

5.6.7 Standard objects

Index 1000 Device type

Index (hex) Name Meaning Data type Flags Default

1000:0 Device type Device type of the EtherCAT slave: the Lo-Word con-

tains the CoE profile used (5001). The Hi-Word con­tains the module profile according to the modular de­vice profile.

Index 1008 Device name

Index (hex) Name Meaning Data type Flags Default

1008:0 Device name Device name of the EtherCAT slave STRING RO ELX3351

Index 1009 Hardware version

Index (hex) Name Meaning Data type Flags Default

1009:0 Hardware version Hardware version of the EtherCAT slave STRING RO 00

Index 100A Software version

Index (hex) Name Meaning Data type Flags Default

100A:0 Software version Firmware version of the EtherCAT slave STRING RO 01

Index 1018 Identity

Index (hex) Name Meaning Data type Flags Default

1018:0 Identity Information for identifying the slave UINT8 RO 0x04 (4
1018:01 Vendor ID Vendor ID of the EtherCAT slave UINT32 RO 0x00000002

1018:02 Product code Product code of the EtherCAT slave UINT32 RO 0x0D1C3052

1018:03 Revision Revision numberof the EtherCAT slave; the low word

(bit 0-15) indicates the special terminal number, the
high word (bit 16-31) refers to the device description

1018:04 Serial number Serial number of the EtherCAT slave; the low byte (bit

0-7) of the low word contains the year of production,
the high byte (bit 8-15) of the low word contains the
week of production, the high word (bit 16-31) is 0

UINT32 RO 0x01681389

(23597961

)

dec

(2

)

dec

(219951186

UINT32 RO 0x00100000

(1048576

dec

UINT32 RO 0x00000000

(0

)

dec

)

dec

)

dec

)

ELX335162 Version: 1.3.1

Parameterization and programming

Index 10F0 Backup parameter handling

Index (hex) Name Meaning Data type Flags Default

10F0:0 Backup parameter

handling

10F0:01 Checksum Checksum across all backup entries of the EtherCAT

Information for standardized loading and saving of
backup entries

slave

UINT8 RO 0x01 (1

UINT32 RO 0x00000000

(0

)

dec

Index 1600 RMB RxPDO-Map Control

Index (hex) Name Meaning Data type Flags Default

1600:0 RMB RxPDO-Map

Control
1600:01 Subindex 001 1. PDO Mapping entry (object 0x7000 (RMB out-

1600:02 Subindex 002 2. PDO Mapping entry (object 0x7000 (RMB out-

1600:03 Subindex 003 3. PDO Mapping entry (object 0x7000 (RMB out-

1600:04 Subindex 004 4. PDO Mapping entry (4 bits align) OCTET-

1600:05 Subindex 005 5. PDO Mapping entry (object 0x7000 (RMB out-

1600:06 Subindex 006 6. PDO Mapping entry (3 bits align) OCTET-

1600:07 Subindex 007 7. PDO Mapping entry (8 bits align) OCTET-

PDO Mapping RxPDO-Map control UINT8 RO 0x07 (7

puts), entry 0x01 (Start calibration))

puts), entry 0x02 (Disable calibration))

puts), entry 0x03 (Input freeze))

OCTET­STRING[10]

OCTET­STRING[10]

OCTET­STRING[10]

RO 0x7000:01, 1

RO 0x7000:02, 1

RO 0x7000:03, 1

RO 0x0000:00, 1

STRING[10]

puts), entry 0x05 (Tara))

OCTET­STRING[10]

RO 0x7000:05, 1

RO 0x0000:00, 3

STRING[10]

RO 0x0000:00, 8

STRING[10]

dec

)

dec

)

Index 1800 RMB TxPDO-Par Status

Index (hex) Name Meaning Data type Flags Default

1800:0 RMB TxPDO-Par Sta-

PDO Parameter TxPDO 1 UINT8 RO 0x06 (6

tus

1800:06 Exclude TxPDOs Specifies the TxPDOs (index of TxPDO mapping ob-

jects) that must not be transferred together with Tx-

OCTET­STRING[10]

RO 04 1A 05 1A 06

1A 07 1A 00 00

PDO 1

Index 1801 RMB TxPDO-Par Value (INT32)

Index (hex) Name Meaning Data type Flags Default

1801:0 RMB TxPDO-Par

PDO Parameter TxPDO 2 UINT8 RO 0x06 (6

Value (INT32)

1801:06 Exclude TxPDOs Specifies the TxPDOs (index of TxPDO mapping ob-

jects) that must not be transferred together with Tx-

OCTET­STRING[10]

RO 02 1A 04 1A 05

1A 06 1A 07 1A

PDO 2

Index 1802 RMB TxPDO-Par Value (Real)

Index (hex) Name Meaning Data type Flags Default

1802:0 RMB TxPDO-Par

Value (Real)

1802:06 Exclude TxPDOs Specifies the TxPDOs (index of TxPDO mapping ob-

PDO Parameter TxPDO 3 UINT8 RO 0x06 (6

jects) that must not be transferred together with Tx-

OCTET­STRING[10]

RO 01 1A 04 1A 05

1A 06 1A 07 1A

PDO 3

)

dec

)

dec

)

dec

ELX3351 63Version: 1.3.1

Parameterization and programming

Index 1A00 RMB TxPDO-Map Status

Index (hex) Name Meaning Data type Flags Default

1A00:0 RMB TxPDO-Map

Status
1A00:01 Subindex 001 1. PDO Mapping entry (1 bits align) OCTET-

1A00:02 Subindex 002 2. PDO Mapping entry (object 0x6000 (RMB inputs),

1A00:03 Subindex 003 3. PDO Mapping entry (1 bits align) OCTET-

1A00:04 Subindex 004 4. PDO Mapping entry (object 0x6000 (RMB inputs),

1A00:05 Subindex 005 5. PDO Mapping entry (2 bits align) OCTET-

1A00:06 Subindex 006 6. PDO Mapping entry (object 0x6000 (RMB inputs),

1A00:07 Subindex 007 7. PDO Mapping entry (object 0x6000 (RMB inputs),

1A00:08 Subindex 008 8. PDO Mapping entry (object 0x6000 (RMB inputs),

1A00:09 Subindex 009 9. PDO Mapping entry (4 bits align) OCTET-

1A00:0A Subindex 010 10. PDO Mapping entry (object 0x6000 (RMB inputs),

PDO Mapping RxPDO-Map Status UINT8 RO 0x0A (10

RO 0x0000:00, 1

STRING[10]

entry 0x02 (Overrange))

OCTET­STRING[10]

RO 0x6000:02, 1

RO 0x0000:00, 1

STRING[10]

entry 0x04 (Data invalid))

OCTET­STRING[10]

RO 0x6000:04, 1

RO 0x0000:00, 2

STRING[10]

entry 0x07 (Error))

entry 0x08 (Calibration in progress))

entry 0x09 (Steady state))

OCTET­STRING[10]

OCTET­STRING[10]

OCTET­STRING[10]

RO 0x6000:07, 1

RO 0x6000:08, 1

RO 0x6000:09, 1

RO 0x0000:00, 6

STRING[10]

entry 0x0E (Sync error))

OCTET­STRING[10]

RO 0x6000:10, 1

)

dec

Index 1A01 RMB TxPDO-Map Value (INT32)

Index (hex) Name Meaning Data type Flags Default

1A01:0 RMB TxPDO-Map

PDO Mapping Value (INT32) UINT8 RW 0x01 (1

Value (INT32)

1A01:01 SubIndex 001 1. PDO Mapping entry (object 0x6000 (RMB inputs),

UINT32 RW 0x6000:11, 32

entry 0x11 (Value))

Index 1A02 RMB TxPDO-Map Value (Real)

Index (hex) Name Meaning Data type Flags Default

1A02:0 RMB TxPDO-Map

PDO Mapping Value (real) UINT8 RW 0x01 (1

Value (real)

1A02:01 SubIndex 001 1. PDO Mapping entry (object 0x6000 (RMB inputs),

UINT32 RW 0x6000:12, 32

entry 0x12 (Value (real)))

Index 1C00 Sync manager type

Index (hex) Name Meaning Data type Flags Default

1C00:0 Sync manager type Using the sync managers UINT8 RO 0x04 (4
1C00:01 SubIndex 001 Sync-Manager Type Channel 1: Mailbox Write UINT8 RO 0x01 (1
1C00:02 SubIndex 002 Sync-Manager Type Channel 2: Mailbox Read UINT8 RO 0x02 (2
1C00:03 SubIndex 003 Sync-Manager Type Channel 3: Process Data Write

(Outputs)

1C00:04 SubIndex 004 Sync-Manager Type Channel 4: Process Data Read

(Inputs)

UINT8 RO 0x03 (3

UINT8 RO 0x04 (4

)

dec

)

dec

)

dec

)

dec

)

dec

)

dec

)

dec

Index 1C12 RxPDO assign

Index (hex) Name Meaning Data type Flags Default

1C12:0 RxPDO assign PDO Assign Outputs UINT8 RW 0x02 (2
1C12:01 Subindex 001 1. allocated RxPDO (contains the index of the associ-

ated RxPDO mapping object)

1C12:02 Subindex 002 2. allocated RxPDO (contains the index of the associ-

ated RxPDO mapping object)

UINT16 RW 0x1600 (5632

UINT16 RW -

)

dec

)

dec

ELX335164 Version: 1.3.1

Parameterization and programming

Index 1C13 TxPDO assign

Index (hex) Name Meaning Data type Flags Default

1C13:0 TxPDO assign PDO Assign Inputs UINT8 RW 0x03 (3
1C13:01 Subindex 001 1. allocated TxPDO (contains the index of the associ-

UINT16 RW 0x1A00 (6656

)

dec

ated TxPDO mapping object)

1C13:02 Subindex 002 2. allocated TxPDO (contains the index of the associ-

UINT16 RW 0x1A01 (6657

ated TxPDO mapping object)

1C13:03 Subindex 003 3. allocated TxPDO (contains the index of the associ-

UINT16 RW -

ated TxPDO mapping object)

Index 1C32 SM output parameter

Index (hex) Name Meaning Data type Flags Default

1C32:0 SM output parameter Synchronization parameters for the outputs UINT8 RO 0x20 (32
1C32:01 Sync mode Current synchronization mode:

UINT16 RW 0x0000 (0

• 0: Free Run

• 1: Synchron with SM 2 Event

• 2: DC-Mode - Synchron with SYNC0 Event

• 3: DC-Mode - Synchron with SYNC1 Event

1C32:02 Cycle time Cycle time (in ns):

• Free Run: Cycle time of the local timer

UINT32 RW 0x001E8480

(2000000

• Synchronous with SM 2 event: Master cycle
time

• DC mode: SYNC0/SYNC1 Cycle Time

1C32:03 Shift time Time between SYNC0 event and output of the out-

UINT32 RO 0x00000000 (0

puts (in ns, DC mode only)

1C32:04 Sync modes sup-

ported

Supported synchronization modes:

• Bit 0 = 1: free run is supported

UINT16 RO 0x0001 (1

• Bit 1 = 1: Synchronous with SM 2 event is
supported

• Bit 2-3 = 01: DC mode is supported

• Bit 4-5 = 10: Output shift with SYNC1 event
(only DC mode)

• Bit 14 = 1: dynamic times (measurement
through writing of 0x1C32:08)

1C32:05 Minimum cycle time Minimum cycle time (in ns) UINT32 RO 0x000186A0

(100000

1C32:06 Calc and copy time Minimum time between SYNC0 and SYNC1 event (in

UINT32 RO 0x00000000 (0

ns, DC mode only)
1C32:07 Minimum delay time UINT32 RO 0x00000000 (0
1C32:08 Command • 0: Measurement of the local cycle time is

UINT16 RW 0x0000 (0

stopped

• 1: Measurement of the local cycle time is
started

The entries 0x1C32:03, 0x1C32:05, 0x1C32:06,
0x1C32:09, 0x1C33:03, 0x1C33:06, 0x1C33:09 [}65]

are updated with the maximum measured values.
For a subsequent measurement the measured val­ues are reset

1C32:09 Maximum Delay time Time between SYNC1 event and output of the out-

UINT32 RO 0x00000000 (0

puts (in ns, DC mode only)

1C32:0B SM event missed

counter

1C32:0C Cycle exceeded

counter

Number of missed SM events in OPERATIONAL (DC
mode only)

Number of occasions the cycle time was exceeded in
OPERATIONAL (cycle was not completed in time or

UINT16 RO 0x0000 (0

UINT16 RO 0x0000 (0

the next cycle began too early)

1C32:0D Shift too short counter Number of occasions that the interval between

UINT16 RO 0x0000 (0
SYNC0 and SYNC1 event was too short (DC mode
only)

1C32:20 Sync error The synchronization was not correct in the last cycle

BOOLEAN RO 0x00 (0
(outputs were output too late; DC mode only)

)

dec

dec

)

dec

dec

)

dec

dec

dec

dec

dec

)

dec

)

dec

)

dec

)

)

dec

)

)

dec

)

dec

)

)

dec

)

)

)

ELX3351 65Version: 1.3.1

Parameterization and programming

Index 1C33 SM input parameter

Index Name Meaning Data type Flags Default

1C33:0 SM input parameter Synchronization parameters for the inputs UINT8 RO 0x20 (32
1C33:01 Sync mode Current synchronization mode:

UINT16 RW 0x0000 (0

• 0: Free Run

• 1: Synchronous with SM 3 event (no outputs
available)

• 2: DC - Synchronous with SYNC0 Event

• 3: DC - Synchronous with SYNC1 Event

• 34: Synchronous with SM 2 event (outputs
available)

1C33:02 Cycle time as 0x1C32:02 UINT32 RW 0x001E8480

(2000000

1C33:03 Shift time Time between SYNC0 event and reading of the in-

UINT32 RO 0x00000000 (0

puts (in ns, only DC mode)

1C33:04 Sync modes sup-

ported

Supported synchronization modes:

• Bit 0: free run is supported

UINT16 RO 0x0001 (1

• Bit 1: synchronous with SM 2 event is
supported (outputs available)

• Bit 1: synchronous with SM 3 event is
supported (no outputs available)

• Bit 2-3 = 01: DC mode is supported

• Bit 4-5 = 01: input shift through local event
(outputs available)

• Bit 4-5 = 10: input shift with SYNC1 event (no
outputs available)

• Bit 14 = 1: dynamic times (measurement
through writing of 0x1C32:08 or 0x1C33:08)

1C33:05 Minimum cycle time as 0x1C32:05 UINT32 RO 0x000186A0

(100000

1C33:06 Calc and copy time Time between reading of the inputs and availability of

UINT32 RO 0x00000000 (0

the inputs for the master (in ns, only DC mode)
1C33:07 Minimum delay time UINT32 RO 0x00000000 (0
1C33:08 Command as 0x1C32:08 UINT16 RW 0x0000 (0
1C33:09 Maximum Delay time Time between SYNC1 event and reading of the in-

UINT32 RO 0x00000000 (0

puts (in ns, only DC mode)
1C33:0B SM event missed

as 0x1C32:11 UINT16 RO 0x0000 (0

counter

1C33:0C Cycle exceeded

as 0x1C32:12 UINT16 RO 0x0000 (0

counter
1C33:0D Shift too short counter as 0x1C32:13 UINT16 RO 0x0000 (0
1C33:20 Sync error as 0x1C32:32 BOOLEAN RO 0x00 (0

)

dec

dec

)

dec

dec

)

dec

dec

dec

dec

dec

)

dec

)

)

dec

)

)

dec

)

dec

)

)

dec

)

)

)

Index F000 Modular device profile

Index (hex) Name Meaning Data type Flags Default

F000:0 Modular device profile General information for the modular device profile UINT8 RO 0x02 (2
F000:01 Module index dis-

tance
F000:02 Maximum number of

modules

Index spacing of the objects of the individual chan-

UINT16 RO 0x0010 (16

nels
Number of channels UINT16 RO EL3351-0000:

0x0001 (1

)

dec

dec

)

dec

EL3351-0090:
0x0002 (2

)

dec

Index F008 Code word

Index (hex) Name Meaning Data type Flags Default

F008:0 Code word reserved UINT32 RW 0x00000000

(0

)

dec

ELX335166 Version: 1.3.1

)

Parameterization and programming

Index F010 Module list

Index (hex) Name Meaning Data type Flags Default

F010:0 Module list Max. subindex UINT8 RW 0x02 (2

)

dec

F010:01 SubIndex 001 RMB UINT32 RW 0x00000172

(370

)

dec

F010:02* SubIndex 002 TSC UINT32 RW 0x000003B6

(950

)

dec

*) ELX3351-0090 only

ELX3351 67Version: 1.3.1

Appendix

6 Appendix

6.1 EtherCAT AL Status Codes

For detailed information please refer to the EtherCAT system description.

6.2 UL notice

Application

Beckhoff EtherCAT modules are intended for use with Beckhoff’s UL Listed EtherCAT Sys­tem only.

Examination

For cULus examination, the Beckhoff I/O System has only been investigated for risk of fire
and electrical shock (in accordance with UL508 and CSAC22.2 No.142).

For devices with Ethernet connectors

Not for connection to telecommunication circuits.

Basic principles

Two UL certificates are met in the Beckhoff EtherCAT product range, depending upon the components:

1. UL certification according to UL508. Devices with this kind of certification are marked by this sign:

2. UL certification according to UL508 with limited power consumption. The current consumed by the de­vice is limited to a max. possible current consumption of 4A. Devices with this kind of certification are
marked by this sign:

Almost all current EtherCAT products (as at 2010/05) are UL certified without restrictions.

Application

If terminals certified with restrictions are used, then the current consumption at 24VDC must be limited
accordingly by means of supply

• from an isolated source protected by a fuse of max. 4A (according to UL248) or

• from a voltage supply complying with NECclass2.
A voltage source complying with NECclass2 may not be connected in series or parallel with another
NECclass2compliant voltage supply!

These requirements apply to the supply of all EtherCAT bus couplers, power adaptor terminals, Bus
Terminals and their power contacts.

ELX335168 Version: 1.3.1

Appendix

6.3 Support and Service

Beckhoff and their partners around the world offer comprehensive support and service, making available fast
and competent assistance with all questions related to Beckhoff products and system solutions.

Beckhoff's branch offices and representatives

Please contact your Beckhoff branch office or representative for local support and service on Beckhoff
products!

The addresses of Beckhoff's branch offices and representatives round the world can be found on her internet
pages:

http://www.beckhoff.com

You will also find further documentation for Beckhoff components there.

Beckhoff Headquarters

Beckhoff Automation GmbH & Co. KG

Huelshorstweg 20
33415 Verl
Germany

Phone: [phone]
Fax: [phone]
e-mail: [e-mail]

Beckhoff Support

Support offers you comprehensive technical assistance, helping you not only with the application of
individual Beckhoff products, but also with other, wide-ranging services:

• support

• design, programming and commissioning of complex automation systems

• and extensive training program for Beckhoff system components

Hotline: [phone]
Fax: [phone]
e-mail: [e-mail]

Beckhoff Service

The Beckhoff Service Center supports you in all matters of after-sales service:

• on-site service

• repair service

• spare parts service

• hotline service

Hotline: [phone]
Fax: [phone]
e-mail: [e-mail]

ELX3351 69Version: 1.3.1

Table of figures

Table of figures

Fig. 1 ELX1052-0000 with date code 32180000, BTN 10000100 and Ex marking ............................... 9

Fig. 2 ELX9012 with date code 32180005 and Ex marking................................................................... 10

Fig. 3 1-channel analog input terminal for strain gauge, 16 bit, Ex i...................................................... 11

Fig. 4 Valid arrangement of the ELX terminals (right terminal block). ................................................... 16

Fig. 5 Valid arrangement - terminals that do not belong to the ELX series are set before and after the

ELX terminal segment. The separation is realized by the ELX9560 at the beginning of the ELX

terminal segment and two ELX9410 at the end of the ELX terminal segment. ........................... 16

Fig. 6 Valid arrangement - multiple power supplies by ELX9560, each with an upstream ELX9410. ... 16

Fig. 7 Valid arrangement - ELX9410 in front of an ELX9560 power supply terminal............................. 17

Fig. 8 Invalid arrangement - missing ELX9560 power supply terminal.................................................. 17

Fig. 9 Invalid arrangement - terminal that does not belong to the ELX series within the ELX terminal

segment....................................................................................................................................... 17

Fig. 10 Invalid arrangement - second ELX9560 power supply terminal within the ELX terminal seg-

ment without an upstream ELX9410............................................................................................ 17

Fig. 11 Invalid arrangement - missing ELX9012 bus end cover. ............................................................. 18

Fig. 12 Installation position and minimum distances ............................................................................... 19

Fig. 13 Attaching on mounting rail ........................................................................................................... 20

Fig. 14 Disassembling of terminal............................................................................................................ 21

Fig. 15 Standard wiring............................................................................................................................ 22

Fig. 16 Connecting a cable on a terminal point ....................................................................................... 22

Fig. 17 ELX3351 - Contact assignment ................................................................................................... 24

Fig. 18 ELX3351 - Connection of a full bridge in 6-wire technology ........................................................ 25

Fig. 19 Strain gauge ................................................................................................................................ 26

Fig. 20 quarter, half, and full bridge ......................................................................................................... 27

Fig. 21 4-wire connection......................................................................................................................... 28

Fig. 22 6-wire connection......................................................................................................................... 28

Fig. 23 Example of a load cell.................................................................................................................. 29

Fig. 24 Parallel strain gauge .................................................................................................................... 31

Fig. 25 Max. input voltages...................................................................................................................... 33

Fig. 26 Parallel connection with ELX3351 ............................................................................................... 34

Fig. 27 ELX3351 - Block diagramm ......................................................................................................... 35

Fig. 28 Notch characteristic/amplitude curve and step response of the FIR filter.................................... 35

Fig. 29 Step response of the IIR filter ...................................................................................................... 36

Fig. 30 Effect of dynamic IIR filters .......................................................................................................... 37

Fig. 31 InputFreeze example ................................................................................................................... 39

Fig. 32 Idling recognition example ........................................................................................................... 40

Fig. 33 Adaptation to the sensor curve .................................................................................................... 41

Fig. 34 Zero calibration with command 0x0101 in CoE object 0xFB00:01 .............................................. 42

Fig. 35 Loading with reference load, command 0x0102 in CoE object 0xFB00:01 ................................. 42

Fig. 36 Control word, tare ........................................................................................................................ 44

Fig. 37 Full scale value, measuring span ................................................................................................ 45

Fig. 38 SE and DIFF module as 2-channel version ................................................................................. 47

Fig. 39 2-wire connection......................................................................................................................... 49

Fig. 40 Common-mode voltage (Vcm)..................................................................................................... 50

Fig. 41 Recommended operating voltage range...................................................................................... 51

ELX335170 Version: 1.3.1

Table of figures

Fig. 42 Signal processing analog input.................................................................................................... 51

Fig. 43 Diagram signal delay (step response) ......................................................................................... 53

Fig. 44 Diagram signal delay (linear) ....................................................................................................... 53

Fig. 45 ELX3351 – process data selection in the TwinCAT System Manager ........................................ 54

Fig. 46 ELX3351 - selection Predefined PDO Assignment...................................................................... 55

Fig. 47 ELX3351 - Default process image ............................................................................................... 56

Fig. 48 Load value in floating-point representation.................................................................................. 57

ELX3351 71Version: 1.3.1