EET - 126
INSTRUMENTATION 1
School of Engineering Technology & Applied Science
(SETAS)
Week: 2
Introduction to Industrial
Control Systems.
1
Objectives
 Explain the difference between an open
and closed loop systems.
 List the factors that affect the dynamic
response of a closed-loop system.
 Describe the operation of Feed-Forward
Control.
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Industrial control systems
 Open-loop
system
 Closed-loop
system.
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Open-Loop System.
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Closed-Loop Systems
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Closed-Loop Systems
Manufacturing applications that require continuous
monitoring and self-correcting action of the operation
for long periods of time without interruption.
Automatic closed-loop configuration
 Performs the self-correcting function
 Employs a feedback loop to keep track of how closely
the system is doing the job it was commanded to do
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Elements of Open- and Closed-Loop Systems
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Open-loop system.
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The basic concept of feedback control is that an
error must exist before some corrective action
can be made.
An error can develop in one of three ways:
1. The set point is changed.
2. A disturbance appears.
3. The load demand varies.
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Process techniques commonly
performed to achieve:
 Quality
 Efficiency
 Safety standards.
Process Control
 Batch Processes
 Continuous Processes.
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Controlling the Quantity of Raw
Materials
In a batch process, exact quantities of raw
materials are required for each batch.
Measurements can be made by
 Weight
 Level
 Volumetric flow rate
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Reaction
 Endothermic
Processes that require a source of
external heat while forming a product
 Exothermic
Processes that require a source
of cooling thermal energy
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Types of Batch Processes

Mixing / Blending

Chemical Reaction

Separation

Polymerization
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Mixing / Blending
Is an operation that involves combining two or
more ingredients together.
Chemical Reaction
Is the process of combining two or more
materials or reactants to form a product.
Separation
An ingredient is removed from a
mixture.
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Polymerization
Is a process in which a large number of
molecules are combined to form a product.
Continuous Processes
Raw materials are continuously passed through
manufacturing equipment at a controlled rate, and the
end product is continuously withdrawn.
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Control Requirements
 Quantity of Raw Materials
 Operating Parameters During the
Process
Operating Parameters





Temperature
Pressure
Level
Flow
Product Composition
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Automation
The control of an industrial process by
automatic rather than manual means
Automated System
 Control
 Manipulation
 Measurement
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Block diagram of a closed-loop automated system
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Response time
Amount of time the sensor takes to respond to
a change in the measured variable.
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Accuracy
Is used to describe how closely a sensor measures
the actual value of a controlled variable.
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Precision
The term precision is used to describe how
consistently a sensor responds to the same
input value
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Linearity
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Hysteresis Loop.
The upward and downward arrows describe the way in
which the output reading varies as the measured signal
applied to its input increases and decreases.
Hysteresis is the dissimilarity
between these two curves.
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Dead space
The sensor will not produce an output
change in response to a range of input
values
The dead space of a
sensor that has poor
sensitivity.
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Sensors
Are primarily mechanical devices or electronic
instruments, and they produce many types of signals
that represent the condition of the controlled variable.
Transmitters
Transmitter, has two functions:
 Converts a signal from the sensor into a standardized
signal used in process systems.
 Carries the signal the distance between the sensor
and the controller.
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