Fieldbus 1 Physical Layer Fieldbus Physical Layer

Fieldbus 2 l FOUNDATION Specification l kbit/s Physical Layer Profile l Document FF-816 l Revision 2.0; Sept 2001 l IEC : 2000 l Fieldbus Standard for Use in Industrial Control Systems l Part 2 : Physical Layer Specification and Service Definition l ISA-S l Fieldbus Standard for Use in Industrial Control Systems l Part 2 : Physical Layer Specification and Service Definition Specifications

Fieldbus 3 Analog loop 4-20 mA Fieldbus loop kb/s digital data TT Multiple variables + Device diagnostics Single variable Analog vs Digital operation Analog instrument Digital instrument

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

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

Fieldbus 6 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

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

Fieldbus 8 Cable specification Recommended maximum length 680 m

Fieldbus 9 l Type ‘A’ cable typically offers the following at 25 O C : l characteristic impedance at kHz : 100  ± 20% l max attenuation at 39kHz (1.25 x 31.25) : 3.0 dB/km l max capacitive unbalance to shield : 4nF/km, tested using a 30m or longer sample l max d.c. resistance (per conductor) : 24  /km l max propagation delay change 8kHz to 39kHz : 1.7 us/km l conductor cross sectional area : 0.8 mm 2 : (18 AWG) l min shield coverage shall be 90% Fieldbus Cables 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 10 R L C R L C R L C Characteristic Impedance l Type ‘A’ cable typically offers the following at 25 O C : l characteristic impedance at kHz : 100  ± 20% l max attenuation at 39kHz (1 1 / 4 x 31.25) : 3.0 dB/km l decibels = 20 log (V in / V out ) l max capacitive unbalance to shield : 4nF/km l max d.c. resistance (per conductor) : 24  /km characteristic impedance at kHz

Fieldbus 11 Fieldbus Cables : to IEC & IEC Cat C flame test All Belden cables are : Low Smoke Non Halogen (LSNH) : optional in steel wire armour (SWA) : outer covering in orange PVC Belden UK Ltd. 10 Watergate Row Watergate Street Chester, Cheshire, UK CH1 2LD Tel +44 (0) Lapp Kerpen BICC Cables

Fieldbus 12 metres Maximum spur lengths are the same irrespective of cable type Recommended spur lengths Figures not absolute

Fieldbus 13 T Max length Type ‘A’ : 1900 m Max length Type ‘C’ : 400 m 1200 / / 400 = 1.13 result > unity : not recommended Type ‘A’ 1200m (1900) Mixing cable types Type ‘C’ 200m (400) T The ability to power the field devices over the network is considered in detail later Communication limitations