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,
pressure, level, flow)
FINAL
CONTROL
ELELMENT(valve)
Measuring
Means
(transmitter)
Process Variable (PV)
ControlledVariable
ActuatingInput
pH, conductivity, humidity,
density, consistency, etc.
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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,
pressure, level, flow)
FINALCONTROL
ELELMENT(valve)
Measuring
Means
(transmitter)
Process Variable (PV)
Controlled
Variable
Actuating
Input
pH, conductivity, humidity,
density, consistency, etc.
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,
pressure, level, flow)
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
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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