1. What is a Sensor?
- There are numerous definitions as to what a
sensor is but I would like to define a Sensor as an
input device which provides an output (signal) with
respect to a specific physical quantity (input).
- It is a device that converts signals from one energy
domain to electrical domain. The definition of the
Sensor can be better understood if we take an
example in to consideration.
4. TEMPERATURE SENSOR
• One of the most common and
most popular sensors is the
Temperature Sensor. A
Temperature Sensor, as the
name suggests, senses the
temperature i.e., it measures the
changes in the temperature.
• Temperature Sensors can be analog or digital.
> Analog Temperature Sensor, the changes in the Temperature correspond to
change in its physical property like resistance or voltage. LM35 is a classic
Analog Temperature Sensor.
>Digital Temperature Sensor, the output is a discrete digital value (usually,
some numerical data after converting analog value to digital value).
5. • There are different types of Temperature Sensors like
Temperature Sensor ICs (like LM35, DS18B20), Thermistors,
Thermocouples, RTD (Resistive Temperature Devices), etc.
• A device which gives temperature measurement as an
electrical signal. This electrical signal will be in the form of
electrical voltage and its proportional to the temperature
DIFFERENT TYPE OF SENSOR USE IN MEASURING
A. Contact Type Temperature Sensor
B. Non-contact Type Temperature Sensor
6. Contact Type Temperature Sensor
• have the ability to measure their own temperature—if there is no heat transfer
between the sensor and the item it is attached to, the sensor can correctly gauge
the temperature. However, it is possible for errors to occur, especially when
measuring surface temperature or attempting to take the temperature of a moving
surface. Depending on the specific application, one of several types of contact
sensors may be appropriate.
• This type of contact sensor is extremely useful and versatile. They are affordable,
easy to replace, and have standardized connectors. They measure the temperature
between two points, not the absolute temperature. A cold junction is often
incorporated into the thermocouple, to provide a set known temperature as a
frame of reference. One drawback, however, is that thermocouples lack a high
level of accuracy. There are multiple different kinds of thermocouples and an array
of applications within each subcategory.
• The word thermistor is a combination of the
words thermal and resistor. The name is apt given thermistors are a type
of resistor whose resistance is proportional to its temperature. They are
often used as temperature sensors, but can also be uses as self-regulating
heating devices and over-current protectors. Similar to resistance
temperature detectors, the primary difference lies in the material used—
thermistors tend to be made of ceramic material or a polymer whereas
resistance temperature detectors tend to be made of metal. There are two
common types of thermistors: positors, or positive temperature
coefficients, and negative temperature coefficient thermistors. If the
resistance increases with increase in temperature, the thermistor is said to
be a positor. If the resistance decreases with increase in temperature, the
thermistor is said to be a negative temperature coefficient. Negative
temperature coefficient thermistors are commonly used as resistance
thermometers in low-temperature measurements, and digital
• They are also used to monitor temperature in automotive functions, such
as gauging fluid temperatures inside the engine.
8. 3.Liquid-in-glass Thermometers
• Perhaps one of the earliest models of contact temperature sensors,
this type of sensor is an earlier version of the thermometers used
to measure human temperature and check for illness, when the
simple use of heat to elevate mercury produced temperature
readings. Today, use of mercury-based thermometers is limited due
to the risk associated with accidental exposure.
4.Resistance Temperature Detectors (RTDs)
• RTDs are often used in place of thermistors and thermocouples in
industrial applications, because they operate in much the same
fashion but are comprised of metal (usually platinum, although iron
and copper are sometimes used) instead of ceramic or polymer.
They are highly stable, accurate, and depend on an electrical power
source to function. Additionally, they have a wide operating range
and are suitable for precise applications. However, there are often
unsuitable for applications above 660 degrees C, and are less
sensitive than thermistors to more subtle temperature changes.
9. 4.Bimetallic Thermometers
• Because two metals will expand at different rates when exposed to
an increase in temperature, bimetallic thermometers measure
temperature by the gap created when the metals expand. Steel and
copper strips, joined lengthwise by welding or brazing, bend as a
result of expansion when heated, and will bend in the opposite
direction when cooled. Bimetallic thermometers are often used in
5.Phase Change Devices
• Similar in theory to strips the measure pH by changing color to
indicate a certain level of acidity, phase change devices register a
physical change commensurate with the change in temperature.
Such devices are often useful in monitoring temperature related
progress, as in cooking.
10. Non-contact Type Temperature Sensor
• refer to ones that have the ability to function without the
need to physically touch the object being monitored. For
example, rather than using an oral thermometer to measure a
patient’s temperature (which requires the thermometer to be
physically placed in the patient’s mouth so that the
thermometer bulb can make contact), a nurse or physician
may employ an infrared thermometer. This type of
thermometer is an example of non-contact sensor technology
that uses infrared radiation to establish a temperature reading
– thus avoiding the need for direct physical contact to occur.
11. 1.Air Sensing or Gauging Technology
• With air gauging, a flow of pressurized air is used to measure the dimensions of
parts or distances such as diameters or tapers. The technology relies on the
principle that as the distance between the air gauge and the object being
measured decreases, the flow rate drops while the air pressure increases. Similarly,
increasing the separation distance increases the flow rate and decreases pressure.
These changes can be measured and used to establish measured values of
distance for parts.
2.Hall Effect Sensor Technology
• The Hall effect allows non-contact sensors to be created that can detect the
presence of a magnetic field and generate an electrical output signal whose value
is proportional to the strength of the field. Hall effect sensors use a thin,
rectangular piece of p-type semiconductor material to which a constant DC voltage
is applied. When the sensor material is brought in proximity to an external
magnetic field, the lines of magnetic flux exert a net force on the charge carriers in
the sensor, resulting in a deposition of like charge carriers (electrons or holes) to
accumulate on opposite sides of the semiconductor material. This charge
accumulation results in an electrical potential difference to develop between these
sides of the material, which can be measured, and which is known as the Hall
voltage. The Hall voltage can then be used as a proxy for how close the sensor is to
the target object, for example.
Non-Contact Sensor Technologies
12. 3.Ultrasonic Sensor Technology
• An ultrasonic sensor makes use of high-frequency sound waves as a
detection or sensing mechanism. For example, to measure distance, the
ultrasonic sensor emits a sound wave towards the target, some portion of
which reflects off of the target and is detected by the sensor. By
measuring the time that it takes for the sound to make a round trip from
the sensor to the target and back again, the distance to the target can be
easily determined. These types of non-contact sensors can work over
relatively long distances, but how well they perform will be a function of
the material composition and shape of the target. A frequent application
is to measure the level of a liquid in tanks.
4.Photonic Sensor Technology
• Photonic or optical sensors use light energy directed through fibers as a
means of determining the displacement from or the distance to the target
object by measuring the intensity of the light that is reflected off the
target. Photonic-based sensors have the advantage of being unaffected by
the presence of EMI emissions or high voltage, but the characteristics of
the target’s surface finish, which determine its reflectivity, can impact the
sensor operation. Additionally, environmental conditions may play a role
in determining if this sensor type is suitable for use in a given application.
13. 5. Capacitive Sensor Technology
• Capacitive sensors rely on detecting a change in capacitance to
provide information about the movement or position of a target. A
capacitor is a device that has the ability to store energy in an
electric field between two plates that are known as electrodes.
With capacitive sensors, the sensor functions as one plate of the
capacitor with the target functioning as the other plate. If a fixed
frequency AC current is applied to the sensor, the amplitude of the
AC voltage will provide a proportional measure of the distance
between the sensor and target.
6.Inductive Sensor Technology
• Inductive sensors make use of magnetic fields generated in coils to
detect motion or the position of a target. One common type of
inductive sensor is a Linear Variable Differential Transformer
or LVDT. A set of coils, one primary and two secondaries, are
contained in the LVDT. When the primary coil is energized with an
AC voltage, induced EMFs are triggered in each of the secondary
coils. By measuring the voltage difference between the two
secondary coils, the sensor can establish the movement of the
target and determine its position.
14. 7.Laser Displacement Sensor Technology
• Laser displacement sensors, also called laser triangulation sensors,
are a non-contact sensor technology that uses the triangulation of
a reflected light beam to establish movement or position of a
target across a measurement range. A semiconductor laser
generates a light beam that is sent through a transmitting lens
towards the target. Light reflected off the target passes through a
receiving lens in the sensor and is focused onto a detector element
such as a CCD (charge-coupled device) array. As the target changes
its position relative to the sensor, the angle of the reflected light
will change which results in that light focusing on a different part of
the detector element. The change in light position can be analyzed
and used to establish the position of the target.
15. Non-contact sensor uses for thermal measurement
• Radiation thermometers gauge temperature based on the radiation released from
an object. An object’s ability to release radiation is called its emissivity—the more
emissive an object is the more radiation a sensor has to work with. Sensors in this
category include spot measuring devices that can produce 1-D and 2-D
temperature readings, as well as thermal imaging thermometers which can display
temperature data as a 2-D image. These types of visual representations are useful
in terms of industrial processes because they can help identify potential problems
or inconsistencies. In turn, the resulting feedback can provide increased quality
and productivity. Radiation thermometers are seen in a vast number of fields,
including playing key role in the medical industry where they monitor human
temperature. Additionally, they can be used to help control and monitor building
temperature and to maintain certain types of power generation.
• Although thermal imagers are a type of radiation thermometer, they possess
several unique characteristics that set them apart. Instead of measuring
temperature based on the radiation at a given point on an object, a thermal
imager can measure a two-dimensional space, in essence providing an accurate
picture of both the source of radiation and the space around it. Thermal imagers
can be used to locate areas in a cord that are overheating, as well as by firefighters
to locate people amid smoke and fire. The devices can also be used to locate heat
leaks in buildings with weak insulation.
16. 3.Optical Pyrometers
• The name pyrometer comes from the Greek, literally meaning “to measure
fire.” Optical pyrometers receive such a meaningful name because they can
gauge temperatures that are too bright to see with the naked eye. A
pyrometer has two parts: an optical system and a detector. To conduct a
proper temperature reading, the optical system works to focus the chosen
region of thermal radiation onto the detector, which in turn translates data
into a readable temperature. This particular type of measuring device is
especially helpful for measuring the temperature of moving objects, or
objects that cannot be touched—it is a useful tool in smelting, where the
temperature of the metal is an essential part of the operation.
4. Fiber Optic Temperature Sensors
• Many fiber optic temperature sensors are merely variations of radiation
thermometers. Relatively simple in design, the fiber optic features an active
sensing device attached to a system that processes the radiation data and
produces a temperature reading. They are extremely useful in automotive
applications because they can set a temperature limit signal for engines.
17. Proximity Sensors
• A Proximity Sensor is a non-
contact type sensor that detects
the presence of an object.
Proximity Sensors can be
implemented using different
techniques like Optical (like
Infrared or Laser), Sound
(Ultrasonic), Magnetic (Hall
Effect), Capacitive, etc.
• Some of the applications of Proximity Sensors are Mobile Phones, Cars
(Parking Sensors), industries (object alignment), Ground Proximity in
18. Infrared Sensor (IR Sensor)
• IR Sensors or Infrared Sensor
are light based sensor that
are used in various
applications like Proximity
and Object Detection. IR
Sensors are used as
proximity sensors in almost
all mobile phones.
• There are two types of Infrared or IR Sensors: Transmissive Type and
>Transmissive Type IR Sensor, the IR Transmitter (usually an IR LED)
and the IR Detector (usually a Photo Diode) are positioned facing
each other so that when an object passes between them, the sensor
detects the object.
> Reflective Type IR Sensor. In this, the transmitter and the detector
are positioned adjacent to each other facing the object.
19. When an object comes in front of the sensor, the infrared light
from the IR Transmitter is reflected from the object and is
detected by the IR Receiver and thus the sensor detects the object.
• Different applications where IR Sensor is implemented
Mobile Phones, Robots, Industrial assembly, automobiles etc.
20. Ultrasonic Sensor
• Ultrasonic Sensor is a non-
contact type device that
can be used to measure
distance as well as velocity
of an object. An Ultrasonic
Sensor works based on the
properties of the sound
waves with frequency
greater than that of the
human audible range.
• Using the time of flight of the sound wave, an Ultrasonic Sensor can
measure the distance of the object (similar to SONAR). The Doppler Shift
property of the sound wave is used to measure the velocity of an object.
21. Light Sensor
• also known as Photo Sensors, Light
Sensors are one of the important
sensors. A simple Light Sensor available
today is the Light Dependent Resistor or
LDR. The property of LDR is that its
resistance is inversely proportional to the
intensity of the ambient light i.e., when
the intensity of light increases, its
resistance decreases and vise-versa.
• By using LDR is a circuit, we can calibrate the changes in its resistance to
measure the intensity of Light. There are two other Light Sensors (or Photo
Sensors) which are often used in complex electronic system design. They
are Photo Diode and Photo Transistor. All these are Analog Sensors.
• There are also Digital Light Sensors like BH1750, TSL2561, etc., which can
calculate intensity of light and provide a digital equivalent value.
22. • The simplest example of a sensor is an LDR or the
Light Dependent Resistor because it is a device
whose resistance varies according to intensity of
light, it is subjected to. When the light falling on an
LDR is more, its resistance becomes very less and
when light is less, the resistance of the LDR becomes
23. Smoke and Gas Sensors
• One of the very useful sensors in
safety related applications are
Smoke and Gas Sensors. Almost
all offices and industries are
equipped with several smoke
detectors, which detect any
smoke (due to fire) and sound
• Gas Sensors are more common in laboratories, large scale kitchens and
industries. They can detect different gases like LPG, Propane, Butane,
Methane (CH4), etc.
24. Alcohol Sensor
• As the name suggests, an Alcohol
Sensor detects alcohol. Usually,
alcohol sensors are used in
breathalyzer devices, which
determine whether a person is
drunk or not. Law enforcement
personnel uses breathalyzers to
catch drunk-and-drive culprits.
TWO CLASSIFITION OF THE SENSOR
1. ACTIVE SENSOR- are those which requires an external excitation signal
or a power signal. (ex. Scanning electron microscope, GPS, and X-ray)
2. PASSIVE SENSOR- do not require any external power signal and directly
generates output response. (ex. Light sensor and infrared sensor)
25. Touch Sensor
• Touch Sensors, as the
detect touch of a
finger or a stylus.
Often touch sensors
are classified into
Almost all modern touch sensors are of Capacitive Types as they are more
accurate and have better signal to noise ratio.
• We do not give much importance to touch sensors but they became an
integral part of our life. Whether you know or not, all touch screen
devices (Mobile Phones, Tablets, Laptops, etc.) have touch sensors in
them. Another common application of touch sensor is trackpads in our
26. Color Sensor
• A Color Sensor is an
useful device in
in the field of image
The TCS3200 is a simple Color Sensor, which can detect any color and
output a square wave proportional to the wavelength of the
27. Humidity Sensor
• Often all humidity sensors
measure relative humidity (a
ratio of water content in air to
maximum potential of air to
hold water). Since relative
humidity is dependent on
temperature of air, almost all
Humidity Sensors can also
• If you see Weather Monitoring Systems, they often provide temperature as
well as humidity data. So, measuring humidity is an important task in many
applications and Humidity Sensors help us in achieving this.
• Humidity Sensors are classified into Capacitive Type, Resistive Type and
Thermal Conductive Type. DHT11 and DHT22 are two of the frequently
used Humidity Sensors in DIY Community (the former is a resistive type
while the latter is capacitive type).
28. Tilt Sensor
• Often used to
Tilt Sensors are one of the simplest and inexpensive sensors out
there. Previously, tilt sensors are made up of Mercury (and
hence they are sometimes called as Mercury Switches) but
most modern tilt sensors contain a roller ball.
29. SPEED SENSOR
• This sensor is used for
detecting speed of an
abject or vehicle.
DIFFERENT TYPE OF SPEED SENSOR
A. Wheel Speed Sensores
D. Ground Speed Radar
E. Pitometer Logs
F. Air Speed Indicators
30. PIR SPEED SENSOR
• An electronic sensor used for
measuring the infrared
radiation emitted from
objects in its field of view.
Every objects that has a
absolutely zero emit heat
energy in the form of
radiation, radiating at
infrared wavelength which is
invisible to the human eye
but can be detected by
special purpose like
electronic devices such as PIR
31. ADVANTAGES OF SENSORS
• Accelerate processes and make them more
• Collect process and asset data in real time
• Monitor processes and assets accurately, reliably
• Increase productivity and reduce total cost of
• Lower energy wastage
• Low cost
• High performance
32. DISADVANTAGES OF SENSOR
• Sensitive to temperature changes or extreme
• Sometimes it cause an error or faulty results
• Distance limitation
• It has more difficulties in reading reflections
from soft, curved, thin and small objects.