Introduction to Fieldbus Foundation Physical LayerIntroduction to Fieldbus Foundation Physical Layer Fazi Hashim – MTL Muhammad Syafiq bin Hamid – KLAESB Product Sales /Application

Introduction to FieldbusFoundation Physical Layer

Fazi Hashim – MTL

Muhammad Syafiq bin Hamid – KLAESB

Product Sales /Application Engineer

Email: [email protected]

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Fieldbus

�What is fieldbus�Benefits of fieldbus�How is fieldbus different to 4-20mA?�Wiring and Interconnection

�Components�Topologies� (Design) tools

� Installation and ‘lessons learned’�Earthing/Grounding

�Communication

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What is fieldbus

(Foundation) Fieldbus:� is all-digital, serial communication system� interconnects “field” equipment such as sensors,

actuators and controllers� is used in both process and manufacturing

automation� has built-in capability to distribute the control

application across the network

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What is fieldbus

Foundation Fieldbus� connects many instruments on the same segment� allows various hazardous area methods on the same

segment (e.g. Ex d and Ex i using fieldbus barriers)– not done so that plant people do not get confused

� provides/requires/uses intelligent field instruments regardless their function, whether temperature, ON/OFF valves, flow, pressure, etc.

� uses standardized device configuration methods DD and EDDL

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Fieldbus Infrastructure

Foundation Fieldbus uses a common FF power supply (or FF IS power supply) compared to multiple isolators and individual wiring

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Benefits of fieldbus

Some of the many benefits of fieldbus:� Faster and easier to design� Greater flexibility (adding/changing devices –

drawings remain unchanged)� Reduced validation, particularly for I.S. (e.g. FISCO)� Higher accuracy (digital data throughout)� Precise timing – improved process control� Reduced components (less isolators, I/O cards), less

wiring, less cabinet space� Less prone to failures (real “Single Loop Integrity”,

e.g. with Redundant FISCO)� Diagnostics are included, and do not need to be

designed-in

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How does it work?

Speed: approx. 25 values per second

Loop time for 3 devices: 100ms (e.g.)

31250 bps (bit per second)

time

mA

Average 15.29mA per device base current

Device 2

Device 3

Device 1

T

Fieldbus

Constant current

+ Fieldbus

42.5 °C, everything ok

36 mbar, but I need maintenance soon, my diaphragm has

built-up

Flow is 0.15 m/s,Temperature is 42.5 °C,

everything ok

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Physical layer elements – Gen. Purpose

Wiringcomponents

HostComputer

H1 Interface

Device 1 Device 3 Device 2

T

Device Coupler& Terminator

(non-IS) Spurs(non-IS) Trunk

FFPST

RedundantFF Power Supply

& Conditioner&Terminator

24VDC

Cable

Power supply / Conditioner

FFPST

Terminators

� Required for all balanced transmission lines (= differential signal not referenced to ground, 0V, earth or so)

� Eliminates reflection (matches cable impedance)

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A ‘terminator’ for light reflections

Physical Layer

� IEC 61158-2 Physical Layer standard � 31.25kbit/s transmission rate� Up to 32 devices per segment - depends on several factors

– Limited to 16 by host– Limited to less by distance– Limited to less by process cycle time– Current “best practice” is “10+2 spare” =12 instruments

� Shielded twisted pair (type A) recommended – can use existing field wiring

� 2-core-cable carries power and signal (like HART)� Up to 1900m (total) with type A cable – up to 9.5km with repeaters

(normally not used)– FISCO IIB: up to 800m trunk practical– Fieldbus barrier: up to 1200m trunk practical

� Up to 120m spur length

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Physical Layer

� Point-to-point ( = 1 device only)- not cost efficient

� Line (bus with spurs)- high maintenance

� Daisy chain- prone to failures

� Chickenfoot (tree)- Highest reliability, best practice

� Can be intrinsically safe

Device connection

Line

Daisy chain

Chickenfoot

Fieldbus Cable

Example: Type A cable: Shielded twisted pair

� Recommended� “Type A” does not specify the diameter; You

can get type A cable in AWG 22, AWG 18, AWG 16, etc

� “Type A” is also available as multipair:as long as individual pairs are twisted and shielded, it is “type A”

Full range of FF Power supplies

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Dual Segment / Redundant

Single Segment Multiple segmentsredundant

8 SegmentsRedundant,High Density

FNICO

FISCO

RedundantFISCO

Entity

For solar powered

applications2x4Segments

N+1 Redundant,

High Density,Flexible power

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Device Coupler (Megablock/fieldbus barrier)

Non-IS / Zone 2

Zone 1 / Ex me

Zone 1/0 / Ex i

Simple & ReliableSolution

Fieldbus BarrierFor advanced

High Energy Trunk

Redundant Fieldbus Barrier

For advancedHigh Energy Trunk

Device Couplers (Megablock/fieldbus barrier)

� Device couplers (recommended):� Connect instruments via spurs� Spurs have individual short circuit protection

� Wiring blocks (not recommended):� Connect instruments via spurs� Spurs do not have short circuit protection

� Fieldbus barriers:� Galvanically isolated device couplers� Provide intrinsically safe (Ex i) spurs� Used for “High Energy Trunk” applications

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Surge on Fieldbus

�New: FS32 Surge Protector

� Plug-on solution� Easily applied to retrofit existing installations with

Megablocks/FBB

Fieldbus topologies

HET

(Redundant)

FISCO

Fieldbus Design Tools (Examples)

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Project Procedure

Best practice:�Bench test

Functional tests and interoperability test�FAT

�SAT

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Portable diagnostic tools

Fieldbus tester FBT-6�Connect at field junction box / FFPS cabinet

�Measures relevant fieldbus parameters�Establishes baseline

after commissioning�Transfer data to PC via USB�Do this regularly for trending data

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Earthing/Grounding

�Grounding in the control room�One point grounding only

�Continuous shield from control room to the field

�Shield not connected at the field instrument

Communication

�Digital communication– e.g. “27.452 °C” or “12.453 mbar”

�Diagnostic always included– e.g. “Good”, “Uncertain”, “Bad”

�Block-based: function blocks (AI/AO/DI/DO/PID/…), transducer blocks (virtualization of the hardware), resource block (device identification)

�Device can contain multiple function blocks– e.g. pressure TX: AI (absolute pressure),

AI (diff. pressure), AI (temperature)22

Communication

�Scheduled communication– Time synchronized

– Deterministic– Precisely periodic (isochronous)

(“macro cycle”)

Leads to higher accuracy in PID control;

Designed for process control

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