InstrumentationOverview Week1 Basic&Intermediate

8/13/2019 InstrumentationOverview Week1 Basic&Intermediate

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What is it?

Definitions of Instrumentation from the Web:

The use of rods, screws, plates, hooks, wires,

bolts, etc. to correct and stabilize abnormalities

of the spine.

The art of composing, orchestrating, or

arranging for an instrumental ensemble.

An electrical or pneumatic device placed in thefield to provide measurement and/or control

capabilities for the system.


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Objectives for this course

Learning the fundamentals of industrial

instrumentation

Terminology and Symbols

Measuring Means

Pressure, Temperature, Level, Flow

Controlling Means Simple Closed Loop Control

PID Loop tuning


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Resources

Text Book :Industrial Control Electronics 3rd edition by Terry Bartelt,

Published by Thompson (Delmar Learning)

ISBN 1 4018 6292 6

ISA (Instrumentation, Systems, and Automation Society)

The International Society for Automation- Setting the

Standard for Automation

www.isatoronto.org

Other web links: see notes
http://www.isatoronto.org/http://www.isatoronto.org/


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Automation Technology

Instrumentation plays an important role in almost everyaspect of Automation Technology.

Industrial Automation

Manufacturing Automation

Process Automation

Building Automation

Everyone needs to measure and/or control somethingandthats what instrumentation is all about.


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Measurement

Things that are measured include:

Pressure, temperature, level, flow, humidity, speed,

motion, position, weight, density, conductivity, pH,

light, quality, quantity, and more.

Devices that process or do the measuring are called:

Sensors, transducers, transmitters, indicators,displays, recorders, data loggers, and data

acquisition systems.


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Controllers

These are the devices that do the controlling: Programmable Logic Controllers (PLCs)

Programmable Automation Controllers (PAC)

Distributed Control Systems (DCS)

Proportional, Integral, Derivative (PID)

Controllers

Supervisory Control and Data Acquisition

(SCADA)

Building Automation Controllers (BAC)

Energy Management Systems (EMS)


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Control Elements

These are the devices the controller

operates:

Pneumatic valves, solenoid valves,

rotary valves, motors, switches, relays,

variable frequency drives.


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Overview of Process Automation

Theprocessis that portion of an automationoperation which use energy measurable bysome quality such as pressure, temperature,level, flow, (and many others) to producechanges in quality or quantity of some material

or energy.

PROCESS

Some Quality or

Quantityof the

Material or Energy

Input

Energy

orMaterial DesiredResult


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Example of a Temperature Process

Heating Element

Water Bath

Temperature

The object ive of this pro cess is to maintain a cons tant water

bath temperature.


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Temperature Process Terminology

Heating Element

Water Bath

Temperature

This is a Temperature Process

The measur ing means is the thermom eter. (Temperature Ind icator - TI)

The process temperature is maintained at a desired po int (Set Point SP)

Steam (Con trol Agent) is used to vary the temperature by openin g andclos ing the con trol valve (Final Con trol Element)


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Level Process

Oil Stock

Level Indicator

Oil Feed to

next

process

The control objective is to maintain a constant liquid level of oil

inside the tank (e.g. 100 gallons +/- 20 gallons). The hand valve is

opened and closed as required to maintain the desired tank level.


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Terminology used to describe the process

PROCESS:Level

CONTROLLED VARIABLE:Head pressure at bottom of tank

CONTROL POINT:The level of oil in the tank (Set Point = 100 gallons)

MEASURING MEANS:Level Indicator (Head Pressure)

CONTROL AGENT:Volume of oil stock

MANIPULATED VARIABLE:Flow rate of oil (gpm)

Oil Stock

Level Indicator

Oil Feed to

next

process


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Basic Model of a Process

The process is maintained at the desired point (SP)by changing the FCE based on the value of the PV

Manipulated

Variable

Desired

Result

Control

Agent

PROCESS

(Temperature,

pressure, level, flow)

FINALCONTROL

ELELMENT(valve)

Measuring

Means

(transmitter)

Process Variable (PV)

Controlled

Variable

Actuating

Input

pH, conductivity, humidity,

density, consistency, etc.

Process equ i l ibr ium (balance) is when the inpu t energy

maintains the output at a constant desired point.


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Basic Model of a Process

The measuring means provides the standardized signalthat represents the condition of the process, i.e. is theprocess at the desired point?

ManipulatedVariable

Desired

Result

Control

Agent

PROCESS

(Temperature,


FINAL

CONTROL

ELELMENT(valve)

Measuring

Means

(transmitter)


ControlledVariable

ActuatingInput




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Measuring Means

Pressure

Level

Flow

Temperature

pH

Humidity

Density

SpeedThermocouples

RTDs / Thermistors

Filled Systems

Bi-metallic

Strain gauge

Piezo-electric

Capacitance

Bourdon Tube

Head meters

(orifice, venturi)

Coriolis, velocity,Mass,

Mechanical Floats

Guided Wave

Weight (load cell)Ultrasonic

Differential Pressure

Transmitters

Pressure Transmitter

Level Transmitter

Differential Pressure

Cell

Flow Transmitter

Temperature Transmitter

Pneumatic

3-15 PSI

Electrical

Current

4 20 mA

0 20 mA

10 50 mA

Voltage

05 V

1 5 V

0 10 V

DigitalON/OFF

Field Bus

ModBus

ProfiBus

HART


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Open Loop Control

Open loop (or manual control) is used whenvery little change occurs in the ProcessVariable (PV)

Manipulated

Variable

Desired

Result

Control

Agent

PROCESS

(Temperature,


FINALCONTROL

ELELMENT(valve)

Measuring

Means

(transmitter)


Controlled

Variable

Actuating

Input



Correct ive act ion is pro vided by manual feedback


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Closed Loop Control

Closed loop or feedback control provides a corrective action based

on the deviation between the PV and the SP

Automatic

Controller Output

(3-15 psi, 4-20mA etc)

CONTROLLING

MEANS

Manipulated

Variable

Desired

Result

Control

Agent

PROCESS

(Temperature,


FINAL

CONTROL

ELELMENT(valve)

MeasuringMeans

(transmitter)

Controller Input (PV)

(3-15psi, 4-20mA etc)

Controlled

Variable

pH, conductivity,

humidity, density,

consistency, etc.

Manual

SP


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Controlling Means

Controllers provide the required control

action to position the FCE at a point

necessary to maintain the PV at the

desired SP.

PID (single loop feedback controller)

DCS (distributed controllers)

PLC (programmable logic controllers)


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Single Loop Feedback Control

1. MeasuringMeans

2. Controlling

Means

3. Final Control

Element

4. Temperature

Process

Temperature Controller and

Recorder

Sensing

Bulb

Temperature

Transmitter

Pneumatic

Control ValveHeat Exchanger

Steam

2

34

1

The TT provides the signal (PV) that represents the condition of theprocess being controlled. The TIC compares the PV to the SP and opens

and closes the FCE to maintain the process at equilibrium.


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Summary

Process automation makes use of instrumentation tomaintain the process at some desired condition.

Common instrumentation used in a process loop are themeasuring means (usually transmitters), the controlling

means (usually a PID controller), and the Final ControlElement (usually some type of valve)

The measuring means provides the feedback signal (PV)used in the process loop. The controlling meansoperates the FCE based on the difference between the

PV and the SP. Process equilibrium is maintained when the difference

between the PV and SP is zero or constant (offset?)


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NEXT?

What are

transmitters?

What is PID? What are P&ID

symbols?

What types

of FCE are

there?

What am I

doing here?

How do I

measure?Pressure

Level

Temperature

Flow

How do I

tune a loop?

What is

Integral

action?

What is a?

FIC

TT

LRC

PRV

Should I usea 3-15 psi or

4-20 mA

valve?

Check out

Documents

InstrumentationOverview Week1 Basic&Intermediate