FieldBus, the wave of the futureFieldBus, the wave of the future

Fieldbus ELC-213Fieldbus

Presentation by Clifford T. Johnson, PE, Control Systems Engineer

But I do not recommend it for every system.It should not be used for systems with

less than 100 control loops

The primary reason that the field bus was develop was to save construction cost of wiring individual field devices

back to I/O Cabinets that were used in the early Days of the DCS and PLC. However, it turned out that the

construction costs were offset by the increase in engineering

PC-ControLAB

Today Assignment & Lab ELC-213

Assignment & LabAssignment & Lab•FieldBus, the wave of the future•PC-ControLab: Tuning demo

Bus ELC-213

AS-i (Actuator Sensor Interface)AS-i (Actuator Sensor Interface)

ASi

AS-i is the easiest network to install

IS Easiest to install ELC-213

AS-i is simply 2 wiresAS-i is simply 2 wires

AS-i primarily operates On-Off ball valves that incorporate

a rotary valve monitor that is addressed using

5 position dip switch

ASi

Highlights ELC-213

AS-i Network HighlightsAS-i Network Highlights

Technology Developer AS-i Consortium Introduced 1993

Openness Multiple vendors, 800+ products, 150 Vendors

Type of Network Sensor BusPhysical Media 2-wire cable (flat or round)

Network Topology Bus, Ring, Tree, StarMaximum Devices

- v2.0 31 nodes (or 248 I/O points)- v2.1 62 nodes (or 434 I/O points)- Maximum Distance 100 meters

- Maximum Distance with repeaters 300 meters(max. of 2 repeaters can be used)

ASi

AS-i is the easiest network to install

6

Fieldbus provides two-way, multi-drop digital communication between devices on the plant floor as well as the automation and display systems. Thus, FFB is essentially a Local Area Network (LAN) for field devices.

Fieldbus

Automation and

Display Systems

P

L

F

Process Plant

Foundation Fieldbus Technology (FFB)

Foundation Fieldbus Technology (FFB)

Foundation Fieldbus-USA ELC-213

Hardest to install ELC-213

FFB Plant Network HierarchyFFB Plant Network Hierarchy

Foundation

PlantNetwork

Office Automation• Mainframes • Management

Local AreaNetwork

Automation & Display Systems• DCS’s, PLC’s, PC’s• SCADA, Supervisory Systems

FieldbusNetwork

Instrumentation & Control• Transmitters, Controllers• Valves & Actuators

FFB is the only Fieldbus that provides power to the devices and that makes it very difficult to design & Install

Best overall ELC-213

ProFiBusProcess Field

Bus

ProFiBusProcess Field

Bus

ProFiBus

SIEMENS

ET200C

SIEMENS

ET200C

Bus

R

Star

Ring

Line

FO

RS 485

IEC 1158-2

DeviceNET ELC-213

DeviceNETDeviceNET

By Allen-Bradley

DeviceNET ELC-213

Allen-Bradley Developed DeviceNETAllen-Bradley Developed DeviceNET

For motor controls

What is Ethernet?What is Ethernet?• The IEEE recognizes Ethernet as standard

IEEE802.3• Defines layers 1 & 2• Layer 1 defines cables, connectors &

electrical characteristics• Layer 2 defines frame format, error

checking, and physical addressing (MAC – Medium Access Control)

• The technology that Ethernet uses to determine when nodes can transmit is Carrier Sense, Multiple Access, with Collision Detection or CSMA/CD

Application

Presentation

Session

Transport

Network

Data Link

Physical1

2

3

4

5

6

7

Ethernet ELC-213Not for process control

How does CSMA/CD work?How does CSMA/CD work?• Carrier Sense, Multiple Access, with

Collision Detection (CSMA/CD) is a contention based access method:

– Carrier Sense: listen before sending– Multiple Access: any device can send data

if it doesn’t detect a “busy” signal.• CSMA is analogous to many speaker

phones where only one person can talk at a time

• Collision Detection senses when two nodes attempt to transmit simultaneously

• When a collision is detected, both nodes stop and wait a different, specified, period of time before retrying

• This is the underlying reason that Ethernet is termed non-deterministic

Transmission speed(msec)

_X

Average andStandard Deviation

determinedby network loading

Std. Dev.

Ethernet ELC-213Non Deterministic

Ethernet – Myth vs. Reality?

Ethernet – Myth vs. Reality?

• Myth: Non-determinism: Any Ethernet network loaded above 40% will experience an exponential growth in transmission delay times and become non-operational.

• Reality: Ethernet delays are linear and can be consistently maintained under 2 ms for a lightly loaded network and 30 ms for a heavily loaded network.

• These delays are inconsequential for most process control applications and can be minimized by using switches and routers to manage network topology.

However, Critical Control & Safety Systems do not use

Ethernet because it is Non-deterministic

Ethernet ELC-213Not for safety systems

FieldBUS Types ELC-213

Fieldbus TypesFieldbus Types

Summary

Sensorbus

• Seriplex• ASI• INTERBUSLoop

Devicebus

• Device Net• SDS• Profibus DP• LONWorks• INTERBUS-S

Fieldbus

• IEC/ISA SP50• Fieldbus Foundation• Profibus PA• HART

Type ofDevices

Type ofControl

ProcessControl

LogicControl

Low-endbit

Midrangebyte

High-endblock

Simple Devices Complex Devices

Easiest

Hardest

Best Overall

PC_ControLAB ELC-213

PC-ControLABPC-ControLAB

Demo

PC-ControLAB is a active demonstration of a control Station that allows you to "TUNE" a simulated controller and view the results.

you will download from resources the instructions for tuning a flow, Temperature and Pressure loop

for optimum controls, then enter the tuning parameters on an email to me as FLOW: Gain=

XX; Reset= XX; (derivative is not used) then the same for PRESS & TEMP

PC_ControLAB ELC-213

PC-ControLABPC-ControLAB

Demo

•User-friendly interface resembles a control station.   •Auto/Manual mode selection buttons and indication •Set point and output entry via "jog" buttons or move Pointer•Tuning permits entry of Proportional Band in % and Reset in repeats/min. •Load control buttons permit forcing a step change or enabling automatic load changes.• You should simulate a load change by simply changing the set point 

PC_ControLAB ELC-213

PC-ControLABPC-ControLAB

Demo

Control menu permits selection of control strategies:

•Feedback•Override (Selector)

•Dual Feedback•Two forms of Feedforward

•Ratio •Two forms of Decoupling

•Cascade•Four forms of Model-Based Control

PC_ControLAB ELC-213

PC-ControLABPC-ControLAB

Demo

Assignment ELC-213

Homework ASSIGNMENT Web LinkHomework ASSIGNMENT Web LinkFind a site of a Pressure Transmitter that works on

Foundation Fieldbus. email web page LINK only to me by Sunday

Email Ex:Email Ex: Johnson-Fieldbus PT- Johnson-Fieldbus PT-AD

Lab: Lab: Johnson-PC_ControLab-Johnson-PC_ControLab-AD

All Emails Subjects and File names must haveAll Emails Subjects and File names must have

You will lose 1-3 points for incorrect subject

Subjects

SubjectSubject::Your last Name-Subject-Assignment Date (AD)

Instrumentation ELC-213

The EndThe End

The End

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