EXPERIMENT NO.1Introduction to the Automatic Controls
labObjectives: To study instruments used for measurement of Level
Temperature Pressure Flow rate To study about various types of
value like Solenoid value Servo Values To study about various types
of controllers like PID controllers which are mostly use in
chemical industries LAYOUT OF INSTUMENTATION AND CONTROL
LABApparatus present in the lab are:
1. Level and flow rate control trainer2. Motor controller
trainer3. Brushless motor drive trainer4. Permanent magnet motor
drive trainer5. Stepper motor6. PID controller7. Transducer
Theoretical Background: Automatic Control: Automatic controlis
the application of control theory for regulation of processes
without direct human intervention. In the simplest type of an
automatic control loop, acontrollercompares a measured value of a
process with a desired set value, and processes the resulting error
signal to change some input to the process, in such a way that the
process stays at its set point despite disturbances.
Designing a system with features of automatic control generally
requires the feeding of electrical or mechanical energy to enhance
the dynamic features of an otherwise sluggish or variant, even
errant system.Components: 1. Sensor: which measure some physical
state such as temperature or level.
2. Controller: which may be from simple physical components up
to complex special purpose digital controllers or embedded
computers?
3. Actuator: which affect a response to the sensor under the
command of the responder, for example, by controlling an energy
input, as e.g. a gas flow to a burner in a heating system or
electricity to a motor in a refrigerator or pump.
General Measurement System:The purpose of a measurement system
is to present an observer with a numerical value corresponding to
the variable being measured. In general, True value is not equal to
measured value. Several measurement systems are in use today.
Before measuring a physical quantity, it is necessary to understand
the working of the measurement system used.Generalized measurement
system is a system that is comprised of the typical elements of a
measurement system. It helps to understand how a measurement system
works.Components of General Measurement System:A generalized
measurement system consists of the following components:
Primary Sensing Element Signal conditioning Element Signal
Processing Element Signal Transmission System Data Presentation
Element
1. Primary Sensing ElementThe primary sensing element receives
signal of the physical quantity to be measured as input. It
converts the signal to a suitable form (electrical, mechanical or
other form), so that it becomes easier for other elements of the
measurement system, to either convert or manipulate it. Sensing
element is in contact with the process and gives an output which
depend in some way on the variable to be measured, .e.g.
Thermocouple, where emf depends on temperature Strain gauges, where
resistance depends on mechanical strain Orifice plate, where
pressure drop depends on flow rate.2. Signal Conditioning
element:Variable conversion element converts the output of the
primary sensing element to a more suitable form. It is used only if
necessary.3. Signal processing element:This takes the output of the
conditioning element and converts it into a form more suitable for
presentation .e.g. A/D converter which converts a voltage into
digital form for input to a computer, while computer calculates the
measured value of the variable from the incoming digital data.4.
Data Transmission System:Data Transmission System is simply used
for transmitting data from one element to another. It acts as a
communication link between different elements of the measurement
system. Some of the data transmission elements used are cables,
wireless antennae, transducers, telemetry systems etc.
5. Data Presentation Element:It is used to present the measured
physical quantity in a human readable form to the observer. LED
displays are most commonly used as data presentation elements in
many measurement systems.
Block diagram of General Measurement System
Signal Conditioning ElementPrimary Sensing ElementPhysical
Quantity to be measured
ObserverData Presentation ElementSignal Processing ElementSignal
Transmission Element
