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Intro to Instrumentation for manufacturing students
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INSTRUMENTATION AND CONTROL
(MCT 3224)
INTRODUCTION TO INSTRUMENTATION
Hasmawati Antong
Lecturer,
Department of Mechatronics Engineering,
International Islamic University Malaysia
Content
Introduction to instrumentation and measurement
Types of instruments
Functions of instruments
Principle of measurement
Measurement systems
Element of process control and instrumentation
Application of instrumentation
Summary
Introduction to instrumentation and
measurement
Instrumentation comprises of scientific activities and
technologies that are related to measurement.
It is a link between physical, chemical and
biological phenomena and their perception by
human
Instrumentation serves to stimulate scientific
knowledge in the junction between theory and
experimental practice
Instrumentation is the science of measurement and
control
Introduction to instrumentation and
measurement
It can be used to refer to two elements:
1) The field in which instrumentation technicians and
engineer work
2) The available methods of measurement and the
instrument which facilitates it
The primary purpose of instrumentation in industrial
manufacturing is to aid the economics of industrial
operation by improving:
1) the quality of the product
2) the efficiency of the production
Introduction to instrumentation and
measurement
Instrument is a device that transforms physical
variable of interest (measurand) into a form that is
suitable for recording (measurement)
Measurement means to employ a standard system
of units by which the reading from one instrument
can be compared with another
Measurand Length
Measurement meter
Types of Instrument
1) Analog instrument
A deflection type instrument
Gives output that varies continuously as the quantity
being measured change
Example:
Types of Instrument
2) Digital instrument
Display the decimal form of the value of the
quantity being measured
The output varies in discrete steps
Example:
Types of Instrument
3) Passive instrument
The output is produced entirely by the quantity
being measured
Example:
• A pressure-measuring device
• Pressure of fluid movement
of pointer against a scale
• No other energy inputs to the
system
Types of Instrument
4) Active instrument
The quantity being measured modulates the
magnitude of an external power source
Example:
• Float-type petrol tank level indicator
• Change in petrol tank level moves potentiometer arm
• Output signal shows proportion of the external voltage source across the potentiometer
Function of Instrument
The common purpose of instruments are to supply
information about the variable quantity being
measured.
Basic functions of instruments:
1) Indicating
2) Recording
3) Controlling
Functions 1) & 2) are for general test instruments
Functions 3) only applicable for industrial process
instruments
Principles of Measurement
Input to the measurement system is the actual value
Output from the measurement system is the measured
value
Measurement System
Measurement system refers to all the software and
hardware that lead from the measured variable to the
processed data.
Measurement System
Sensing element (sensor) : device in contact with the
measured process and giving output depends on the
quantity being measured
Signal conditioning element : takes output from sensor
and converts it to a form suitable for processing
(amplifiers, filter)
Measurement System
Signal processing element : takes output from the
signal conditioner and performs
analysis/transformation (ADC, spectral analyzer)
Data presentation : computer display, graphs,
indicator, gauges, etc
Elements of Process Control and
Instrumentation
1. Process (plant)
Consists of complex assembly of phenomena that relates to some manufacturing sequence
Contain the variable to be controlled
Single-variable process (eg. Control only temperature)
Multi-variable process (eg. Control temperature and humidity)
2. Measurement
To get information about the variable to be controlled
Sensor is used to perform the measurement and also energy conversion (eg. Temperature sensor convert temp. to voltage)
Elements of Process Control and
Instrumentation
3. Controller / Error detector
Used to examine the error and determine the action to be taken (if any)
Error is obtain from the difference between the measured value and the reference value
Its operation usually performed by microprocessor-based computers
4. Setpoint
Refers to the reference value set by user
5. Control Element
The element that exerts the change in the controlled variable
Elements of Process Control and
Instrumentation
Block diagram of a refrigerator process-control loop
Elements of Process Control and
Instrumentation
1) Process the refrigerator and all its contents
2) Measurement a sensor in the refrigerator to measure the internal temperature
3) Controller / error detector controller (relay, PI, PID) to turn on the compressor and fan
4) Setpoint determined by set knob setting
5) Control element compressor and fan circulate the cold air
Application of Instrumentation
1) Regulating trade
Achieved by applying instrument to measure physical quantities such as length, volume and mass in terms of standard units
2) For monitoring
Measurement information allow us to take some prescribe action accordingly
For instance, temperature monitoring in vaccine storage allow us to decide either to increase the cooling rate or not
Applicable in our daily live or to control some industrial process
Application of Instrumentation
3) As part of automatic feedback control system
Elements of a simple closed-loop control system
Summary
Instrumentation involves measurement process and control process
Instrumentation is very important in engineering field because it allows us to measure, observe, control and keep record of the physical process that we are working with.