Omar Al-Mukhtar University
Faculty of Engineering
SUSTAINABLE AND
RENEWABLE ENERGY
ENGINEERING DEPARTMENT
(SREE)
PLC
Sensors
by:
Hameed Alshalwi
20184424
Under
Supervisor
Dr. Omar Ben Ali
Sensors :
They are precise electronic components, or with electronic properties, that convert
and transfer physical quantities, such as temperature, invisible rays, visible rays,
pressure, movement in space, light intensity, and others, into electrical quantities,
represented by a difference in voltage. , or the intensity of the current, or the reversal
of charges, which results in the closure or opening of an electrical circuit.
The idea of sensors working :
There are many mechanisms for the sensors to work, according to the quantity and
physical quality to be sensed, or to be dealt with by the sensor. For example, if the
physical quantity to be dealt with is an optical quantity, then the idea of the sensor is
an electronic resistance, whose resistance is affected when exposed to light by a
certain amount of light.
When the light falls on the resistance in the required amount, the resistance strength
of the electric current decreases, allowing the electric current to pass through the
electrical circuit to the device that is to be operated, and thus the device works as soon
as the light falls on the photo resistor.
Division of sensors :
There are many types of divisions of sensors, some of which are easy, others are more
complex, and in general they can be divided as follows:
i.
the (positive) voltage sensors, Active Sensors
In this type of sensors, it converts the physical quantity to be dealt with, into an
electric current that is connected to the device to be operated, as soon as that physical
quantity is present, and these sensors can work even in the absence of an electrical
supply source, to feed those sensors
An example of this is the photoelectric sensors, which convert the optical quantity
into an electrical quantity, and thus the work of the device to be operated according to
the availability of the optical physical quantity.
ii.
Passive sensors that do not generate electric charges
These sensors need an electric source to feed them, as they work as a variable
electrical resistance, so when exposed to any physical quantity such as movement,
their resistance to the electric current decreases; Which causes the device to be
operated to be closed-connection, so it works as required.
Sensor types :
There are many types of sensors that cover the most required needs, and that reflect
different physical quantities. We can address some of them as follows:
1. Ultrasound sensors : which sense ultrasonic waves and vibrations as a
physical quantity, and are used in radars and others.
2. Proximity sensors : which sense physical quantities related to distance and
location, such as opening a car door when approaching it, as well as smart phone
technology, and others.
3. Thermal sensors : These are sensors that respond to thermal physical
quantities, such as fire alarms, air conditioning operation, microwaves, electronic
thermometers, and others.
4. Pressure sensors : they are of a quality that responds to pressure as a
physical quantity, and are used in military operations, operating engines to raise
water at a certain pressure level, and others.
5. Humidity sensors : They deal with humidity as a physical quantity, and are
used in works that depend on the level of humidity in the atmosphere, for
example.
6. Level sensors : They deal with different levels, such as dealing with the water
level at a certain level, and others.
7. Acceleration sensors : It deals with speed as a physical quantity, and is
often used in cars, such as braking a car at a certain level automatically.
 The use of the sensor system, or automation, is a modern
system that has made work life more accurate, easier to
perform, deeper luxury, and more secure. What the future
contains of technology products will be stranger, and what
exists today will become retrograde work for tomorrow.