Fieldbus Physical Layer 1 Fieldbus Specifications l FOUNDATION

Fieldbus Physical Layer 1

Fieldbus Specifications l FOUNDATION Specification l 31. 25 kbit/s Physical Layer Profile l Document FF-816 l Revision 2. 0; Sept 2001 l ISA-S 50. 02 -1992 l Fieldbus Standard for Use in Industrial Control Systems l Part 2 : Physical Layer Specification and Service Definition l IEC 61158 -2: 2000 l Fieldbus Standard for Use in Industrial Control Systems l Part 2 : Physical Layer Specification and Service Definition 2

Fieldbus Digital Operation T T Host system does not have to be at the network terminator Additional devices may be connected to a Fieldbus network at any point 4 100 R 1 µF

Fieldbus Tree, Spur, & Daisy-chain topology T T Spur Tree Daisy-chain 5 X

Fieldbus Digital Operation T T Up to 32 devices per segment (more with repeaters) Total network length achievable depends on cable quality A maximum of four repeaters recommended 6

Fieldbus max cable lengths 300 m T 10 m 50 m T 60 m 30 m 80 m Adding up all trunk + spurs = 680 metres 7 60 m

Fieldbus Cable specification 680 m 8 Recommended maximum length

Fieldbus 9 Fieldbus Cables l Type ‘A’ cable typically offers the following at 25 OC : l characteristic impedance at 31. 25 k. Hz : 100 ± 20% l max attenuation at 39 k. Hz (1. 25 x 31. 25) : 3. 0 d. B/km l max capacitive unbalance to shield : 4 n. F/km, tested using a 30 m or longer sample l max d. c. resistance (per conductor) : 24 /km l max propagation delay change 8 k. Hz to 39 k. Hz : 1. 7 us/km l conductor cross sectional area : 0. 8 mm 2 : (18 AWG) l min shield coverage shall be 90% l Where the field link is intrinsically safe : l The use of a screened cable l removes the necessity for segregation of IS from non-IS cables for safety reasons l removes the need to assess fault interaction l segregation is desirable to ensure interference is minimised l IS cables should be clearly identified l where colour is used to identify the cables it should be light blue

Fieldbus Characteristic Impedance l Type ‘A’ cable typically offers the following at 25 OC : : 100 ± 20% : 3. 0 d. B/km l characteristic impedance at 31. 25 k. Hz l max attenuation at 39 k. Hz (11/4 x 31. 25) l decibels = 20 log (V in / V out) l max capacitive unbalance to shield l max d. c. resistance (per conductor) : 4 n. F/km : 24 /km characteristic impedance at 31. 25 k. Hz R 10 L C R L C

Fieldbus Cables : to IEC 61158 -2 & IEC 60332 -3 Cat C flame test All Belden cables are Belden UK Ltd. 10 Watergate Row Watergate Street Chester, Cheshire, UK CH 1 2 LD Tel +44 (0)1244 350 535 11 : Low Smoke Non Halogen (LSNH) : optional in steel wire armour (SWA) : outer covering in orange PVC Lapp Kerpen BICC Cables

Fieldbus Recommended spur lengths metres 12 Maximum spur lengths are the same irrespective of cable type s Figure not te absolu

Fieldbus Mixing cable types T Type ‘A’ 1200 m (1900) Type ‘C’ 200 m (400) Communication limitations Max length Type ‘A’ : 1900 m Max length Type ‘C’ : 400 m 1200 / 1900 + 200 / 400 = 1. 13 result > unity : not recommended 13 The ability to power the field devices over the network is considered in detail later T