Introduction to Fieldbus Foundation Physical LayerIntroduction to Fieldbus Foundation Physical Layer...
Transcript of Introduction to Fieldbus Foundation Physical LayerIntroduction to Fieldbus Foundation Physical Layer...
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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