Instrumentation

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Instrumentation

• Leo SaLemi
• September 2008

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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 the
  field 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

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Automation Technology

• Instrumentation plays an important role in almost
  every aspect of Automation Technology.
• Industrial Automation
• Manufacturing Automation
• Process Automation
• Building Automation
• Everyone needs to measure and/or control
  something and thats 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

• The process is that portion of an automation
  operation which use energy measurable by some
  quality such as pressure, temperature, level,
  flow, (and many others) to produce changes in
  quality or quantity of some material or energy.

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Example of a Temperature Process
The objective of this process is to maintain a
constant water bath temperature.
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Temperature Process Terminology
This is a Temperature Process
The measuring means is the thermometer.
(Temperature Indicator- TI)
The process temperature is maintained at a
desired point (Set Point SP)
Steam (Control Agent) is used to vary the
temperature by opening and closing the control
valve (Final Control Element)
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Level 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)

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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

Process equilibrium (balance) is when the input
energy maintains the output at a constant
desired point.
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Basic Model of a Process

• The measuring means provides the standardized
  signal that represents the condition of the
  process, i.e. is the process at the desired point?

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Measuring Means
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Open Loop Control

• Open loop (or manual control) is used when very
  little change occurs in the Process Variable (PV)

Corrective action is provided 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

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
The TT provides the signal (PV) that represents
the condition of the process being controlled.
The TIC compares the PV to the SP and opens and
closes the FCE to maintain the process at
equilibrium.

1. Measuring Means
2. Controlling Means
3. Final Control Element
4. Temperature Process

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Summary

• Process automation makes use of instrumentation
  to maintain the process at some desired
  condition.
• Common instrumentation used in a process loop are
  the measuring means (usually transmitters), the
  controlling means (usually a PID controller), and
  the Final Control Element (usually some type of
  valve)
• The measuring means provides the feedback signal
  (PV) used in the process loop. The controlling
  means operates 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 PID symbols?
What types of FCE are there?
What am I doing here?
What is a?
Check out
How do I tune a loop?
FIC TT LRC PRV
How do I measure? Pressure Level Temperature Flow
Should I use a 3-15 psi or 4-20 mA valve?
What is Integral action?