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SENSOR
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Logical Sensor
Sensors allow a PLC to detect the state of a process.
Logical sensors can only detect a state that is either true orfalse. Examples of physical phenomena that are typically
detected are listed below :
inductive proximity - is a metal object nearby?
capacitive proximity - is a dielectric object nearby?
optical presence - is an object breaking a light beam
or reflecting light?mechanical contact - is an object touching a switch?
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Types of Logical Sensor
Contact Switches
Contact switches areavailable as normallyopen and normallyclosed. Their housings
are reinforced so thatthey can take repeatedmechanical forces. Door Contact Switches
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Types of Logical Sensor
Proximity
Sensors allow
a PLC to detectthe state of a
process
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Types of Logical Sensor
Photo Optics
Optical sensors require both a
light source (emitter) and
detector.
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Types of Logical Sensor
Photo Optics
Emitters will produce lightbeams in the visible and
invisible spectrums usingLEDs and laser diodes.Detectors are typically builtwith photodiodes orphototransistors.
The emitter and detector arepositioned so that an objectwill block or reflect a beamwhen present.
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Types of Logical Sensor
Capacitive
Capacitive sensors are able to detectmost materials at distances up to a fewcentimeters. Recall the basic relationshipfor capacitance.
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Types of Logical Sensor
Capacitive
In the sensor the area
of the plates and
distance betweenthem is fixed. But, the
dielectric constant of
the space around them
will vary as different
materials are brought
near the sensor.
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5. Inductive
Inductive sensors use currentsinduced by magnetic fields to
detect nearby metal objects.
The inductive sensor uses acoil (an inductor) to generate ahigh frequency magnetic field.
If there is a metal object nearthe changing magnetic field,current will flow in the object.
Types of Logical Sensor
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5. InductiveThis resulting current flow sets up a new magnetic field that
opposes the original magnetic field.
The net effect is that it changes the inductance of the coil in theinductive sensor. By measuring the inductance the sensor candetermine when a metal have been brought nearby.
These sensors will detect any metals, when detecting multipletypes of metal multiple sensors are often used.
Types of Logical Sensor
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6.
Ultrasonic
An ultrasonic sensor emits a sound above the normal
hearing threshold of 16KHz. The time that is required for the
sound to travel to the target and reflect back is proportional
to the distance to the target.
Types of Logical Sensor
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6. Ultrasonic
The two common types of sensors are;
electrostatic - uses capacitive
effects. It has longer ranges and
wider bandwidth, but is more
sensitive to factors such as
humidity.
piezoelectric - based on charge
displacement during strain in
crystal lattices. These are rugged
and inexpensive.
These sensors can be very effective for
applications such as fluid levels in tanks and
crude distance measurement.
Types of Logical Sensor
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Logical Sensor and Switches Wiring
(sourcing and sinking)
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Logical Sensor and Switches Wiring
(sourcing and sinking)
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Logical Sensor and Switches Wiring
(sourcing and sinking)
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Logical Sensor and Switches Wiring
(sourcing and sinking)
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Logical Sensor and Switches Wiring
(sourcing and sinking)
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Logical Sensor and Switches Wiring
(sourcing and sinking)
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Logical Sensor and Switches Wiring
(sourcing and sinking)
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Logical Sensor and Switches Wiring
(sourcing and sinking)
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Logical Sensor and Switches Wiring
(sourcing and sinking)
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ACTUATORS
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ACTUATORS
Solenoid
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ACTUATORS
Valves
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Cylinder
ACTUATORS
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Cylinder
ACTUATORS
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Cylinder
ACTUATORS
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Motor
ACTUATORS
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Hydraulic
ACTUATORS
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Electro -Hydraulic
The word electro-hydraulic has two meanings
for two highly different operations. It can
stand for an electrical control device that
makes precise adjustments in a hydraulic
system.
Also, it can mean a chemical reaction that is
created by firing short, powerful electricalimpulses into or directly beneath the surface
of a body of liquid.
ACTUATORS
Electro hydraulic servo valve
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Electro -Hydraulic
Perhaps the most well-known electrohydraulic
device is an automobile's power steeringunit
also called an electrohydraulic actuator.
The unit combines high power with a high degree
of accuracy to adjust for the minute movements
of the steering wheel in a vehicle.
This type of technology, where electrical
components are used to increase the accuracy of
hydraulic movements, can be applied to almost
any situation where hydraulics is used.
ACTUATORS
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Pneumatic
ACTUATORS
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Electro - Pneumatic
The electro-pneumatic action is a control system for pipe organs,
whereby air pressure, controlled by an electric current and
operated by the keys of an organ console, opens and closes valveswithin wind chests, allowing the pipes to speak.
This system also allows the console to be physically detached from
the organ itself.
The only connection was via an electrical cable from the console
to the relay, with some early organ consoles utilizing a separate
wind supply to operate combination
pistons.
ACTUATORS
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