Sensors and Actuators

2. TITLE : SENSORS AND ACTUATORS
BY: MUBASHIR MUSTAFA
57509

3. SENSORS AND ACTUATORS
SENSORS
• Transducer that receives and responds to a
signal or stimulus from a physical system.
• It produces a signal, which represents
information about the system, which is used by
some type of telemetry, information or control
system.

4. ACTUATORS
• A device that is responsible for moving or controlling a
mechanism or system.
• Controlled by a signal from a control system or manual
control.
• Operated by a source of energy, which can be
mechanical force, electrical current, hydraulic fluid
pressure, or pneumatic pressure, and converts that
energy into motion.

5. ACTIVE & PASSIVE SENSOR
ACTIVE SENSORS
Require an external power source to operate, which is called an
excitation signal.
For example, a thermistor.
PASSIVE SENSORS
Generate an electric current in response to an external stimulus
which serves as the output signal
For example a photo diode, a piezoelectric sensor and a
thermocouple.

6. Active element of a sensor is called a transducer.
Transducer:
A device which converts one form of energy to another.
When input is a physical quantity and output electrical → Sensor
When input is electrical and output a physical quantity → Actuator

7. COMMONLY MEASUREABLE PHENOMENA
• BIOLOGICAL and CHEMICAL (Fluid Concentrations (Gas
or Liquid))
• ELECTRIC (Charge, Voltage, Current, Electric Field
(amplitude, phase, polarization), Conductivity,
Permittivity)
• ELECTROMAGNETIC
• HEAT/TEMPERATURE
• MAGNETIC
• MECHANICAL MOTION (DISPLACEMENT, VELOCITY,
ACCELERATION, ETC.)
• OPTICAL (Refractive Index, Reflectivity, Absorption)
• RADIOACTIVITY

8. NEED FOR SENSOR
Sensors are widespread. They are embedded in our bodies,
automobiles, airplanes, cellular telephones, radios, chemical
plants, industrial plants and countless other applications.
Without the use of sensors, there would be no
automation

9. SENSORS WILL BE DISCUSSED
• Vision and Imaging Sensor
• Temperature Sensor
• Radiation Sensor
• Proximity Sensor
• Pressure Sensor
• Particle Sensor
• Motion Sensor
• Metal Sensor
• Level Sensor
• Flow Sensor
• Flame Sensors

10. VISION AND IMAGING SENSORS
Electronic devices that detect:
• Presence of objects or colors
within their fields of view
• Convert information into a visual
image for display.

11. TEMPERATURE SENSORS/DETECTORS
• Detect thermal parameters
• Provide signals to the inputs of control
and display devices.
A temperature sensor typically relies:
• An RTD (Thermocouple)
• A thermistor.

12. RADIATION SENSORS
• Sense the presence of alpha, beta, or gamma particles
• Provide signals to counters and display devices.
Key specifications include
• Sensor type
• Minimum and maximum
detectable energies.
Pyrometer temperature sensor measures the radiant
(energy) heat emitted or reflected by a hot object.

13. PROXIMITY SENSORS
• Detects presence of nearby objects through non-contacting means.
• Range of up to several millimeters
• Produce a usually dc output signal to a controller.
Key specifications include
• Sensor type
• Maximum sensing distance
• Minimum and maximum operating temperatures
• Dimensions of diameter and length.

14. PRESSURE SENSORS
• Detect forces per unit area in gases or liquids.
• Typically uses a diaphragm and strain gage bridge for detection.
Key specifications include
• Sensor function
• Minimum and maximum working pressures
• Full scale accuracy

15. PARTICLE SENSORS/DETECTORS
• Sense dust and other airborne particulates.
Key specifications include
• Transducer type
• Minimum detectable particle size
• Operating temperature range
• Sample volume
• Response time.
Amplification
stage Output

16. MOTION SENSORS
• Sense the movement or stoppage of
parts, people, etc.
Key specifications include
• Sensor type
• Sensor function
• Minimum and maximum speeds.

17. METAL DETECTORS
• Sense The presence of metal in a variety of
situations ranging from packages to people.
• Sensor technologies with electromagnetics
being popular.
Key specifications include
• Maximum sensing distance
• Feature choices like handheld and fixed
systems.

18. LEVEL SENSORS/DETECTORS
• Electronic or electro-mechanical devices
• Used for determining the height of gases, liquids, or solids in
tanks or bins
Typical level sensors use
• Ultrasonic
• Capacitance
• Vibratory
• mechanical
means to determine product height.
Key specifications include:
• Sensor type,
• Sensor function
• Maximum sensing distance

19. LEVEL SENSOR
Level Sensors can be broken into two classifications;
• Point level measurement indicates when a product is present at a
certain point.
• Continuous level measurement indicates the continuous level of a
product as it rises and falls.

20. FLOW SENSORS
• Sense the movement of gases, liquids, or
solids
A flow sensor can be all electronic
• Using ultrasonic detection from outside a
pipeline
• Or partially mechanical—a paddlewheel
that sits and spins directly in the flow
stream itself.
Key specifications include
• Sensor/detector type
• Maximum flow rate
• Maximum working pressure
• Minimum and maximum operating
temperatures.

21. FLAME SENSORS
• Opto-electronic devices used to
sense the presence and quality of
fire.
A flame detector typically relies on
ultraviolet or infrared detection.

22. IMPORTANT ATTRIBUTES
• Types of Sensors/Detectors/Transducers
Sensor types are common among many of the various
subcategories. For example, Hall effect sensors are found in
proximity sensors, level sensors, motion sensors, and so on.
Infrared sensors are used for level sensing, flame detection, etc.
Sensing a fuel level in a tank, say, can be achieved through a
number of sensor types.
• Planned Application
Picking an planned application can help narrow choices for specific
instances.
• Output Types
Many control sensors use 4-20 mA current loops, where 4 mA
represents the low side of the analog signal and 20 mA
represents the high side.
• Response Time
Many sensors have response times measured in milliseconds, while
sensors for gases, leaks, etc. may have their response times
measured in seconds or even minutes.
• Features
Sensors designed to function in extreme environments,
hazardous locations, etc. can be selected here.

23. ACTUATORS
• Component of a machine that is responsible for moving and controlling
a mechanism or system
• For example by opening a valve. In simple terms, it is a "mover".
• It requires a control signal and a source of energy.
• Its main energy source may be
• Electric current
• Hydraulic fluid pressure
• Pneumatic pressure.
When it receives a control signal, an actuator responds by converting the
source energy into mechanical motion.

24. TYPES OF ACTUATORS
1. Electrical actuators
• Electric motors (linear or rotational)
• DC servomotors
• AC motors
• Stepper motors
• Solenoids
• Relay
2. Hydraulic actuators
Use hydraulic fluid as the driving force
3. Pneumatic actuators
Use compressed air as the driving force

25. DC MOTORS
DC motors are widely used:
• Convenience of using direct current. E.g. motors in automobiles.
• Linear Torque-Speed relationship.
One special type of DC motors is Servomotors.
• A feedback back loop is used to control speed.

26. AC MOTORS
Most used in industry.
Advantages:
• Higher power supply
• Ease of maintenance
Two types:
• Induction motor
• Synchronous motor
Synchronous motor
Induction motor

27. STEPPER MOTORS
Provides rotation in the form of discrete
angular displacement (step angles).
Each step angle is actuated by a discrete
electrical pulse.
Are used in open loop control
systems.

28. HYDRAULIC AND PNEUMATIC ACTUATORS
Powered by pressurized fluid.
• Oil for hydraulic systems
• Compressed air for pneumatic systems

29. SOLENOIDS
A movable plunger inside a stationary wire
coil.
Used to open and close valves in fluid flow
systems, e.g., chemical processing
equipment.

30. A CONTROL SYSTEM BLOCK DIAGRAM