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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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