FOUNDATION FIELD BUSPresented ByJERP DCS Team24th Nov 05

Foundation Field bus, H1 is an all-digital, serial, two-way communication system with Speed of 31.25 Kbits /S

ADVANTAGES OF FF

ADVANTAGES OF FF

ADVANTAGES OF FF

Two Types of FF Devices:Bus-Powered 32 DevicesDevices take power from BusRequire 10-30 mA of current between 9 and 32 volts. Non Bus-Powered 16 DevicesDevices take Power over Separate Wires

FF can have different topologies in a networkBusTree (Chicken-foot)Daisy-chainPoint-to-point

TOPOLOGIES OF FF NETWORK

BUS TOPOLOGY

TREE TOPOLOGY

DIASY CHAIN TOPOLOGY

Daisy Chain WiringUse Same Conduit for in and out wires in order to enable removal of device without interrupting bus

POINT TO POINT TOPOLOGY

H1 Physical LayerManchester Biphase-L Technique

Field Bus Signalling

The transmitting device delivers 10 mA at31.25 kbit/s into a 50 ohm equivalent load to create a 1.0 volt peak-to-peak voltage modulated on top of the direct current (DC) supply voltage.The DC supply voltage can range from 9 to 32 volts. However, for Intrinsically Safe (I.S.) applications, the allowed power supply voltage depends on the barrier rating

Total Trunk Length= 1900 mRepeaters ( Max)= 4 Segments ( Max)= 5 Max Spur Length= 120 mUsing Repeaters for 5 Segments,Max Total Cable length = 9500 m

Devices per Spur vs. Spur length

Reducing NoiseEach fieldbus segment must have exactly two terminators. Terminators located in the field should be installed in a junction box;

A terminator is used to prevent reflection at the ends of a field bus cable.This reflection is a form of noise that distorts the signal.

Lightning/Surge Protection

Surge suppression shall consist of low-capacitance silicon avalanche diodes or spark gaps, wired for both normal- and common-mode protection, connected to the electrical safety ground grid.

Field bus Cable SpecificationsAll cables shall be single or multiple twisted pair with an individual shield for each pair. Multi-pair cables shall have an additional overall shield.

Single Pair Field Bus Cable

Total Cable Length

The total length includes the trunk and all spurs.

Barriers

Galvanic IsolatorMaintains safety by having high integrity isolation that prevents the transmission ofelectrical surges or overloads from the safe to the hazardous area

Safety barrier may also function as a Repeater

Intrinsic Safety BarriersCategory Ex-ia : Suitable for all zones, especially Zone 0.Category Ex-ib : Suitable for Zone 1 and Zone 2.

Exi BarriersEntityFISCO - Fieldbus Intrinsically Safe ConceptFNICO - Fieldbus Non-Incendive Concept

FISCO - Fieldbus Intrinsically Safe ConceptMore power more devicesHigher voltage longer cableUsed in Zone 0 100 mA (ia, IIC) ~8 devices/barrier (ia, IIC) 1,000 m ( ia ) 5,000 m ( ib )

FNICOFieldbus Non-Incendive ConceptIt is only applicable to Zone 2 (Division 2). FNICO puts the current limitation on the trunk without any further limitations on the spur.

Flame Proof EnclosureFlameproof Ex d is one way of installing in hazardous areas, but this method is at a disadvantage in field bus, because it is necessary to power down the entire network to service one device.

Power Supply Impedance Module PSI302Requires an Input Voltage of 20-35 VDCIs Redundant, Load Sharing and Output Current LimitedProvides Impedance MatchingConnects Maximum 4 channels per moduleThe power supply impedance has built in functionality for automatic and bumplessswitch over from a main to a backup

Power Supply Impedance Module

A power supply impedance module prevents short circuit of communication signal by the power supply. The power supply impedance also regulates the power supply voltage. If ordinary power supply is used it will absorb signals on the cable, as it will try to maintain a constant voltage level.

Field Devices Execution Time1-second - 12 devices with 4 valves. 0.5 Second- 6 devices with 2 valves. 0.25-second - 3 devices with 1 valve

Thank You