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Sensors: Different Types of Sensors

Sensors are sophisticated devices that are frequently used to detect and respond to electrical or optical signals. A Sensor converts the physical parameter (for example:  temperature, blood pressure, humidity, speed, etc.) into a signal which can be measured electrically. Let’s explain the example of temperature. The mercury in the glass thermometer expands and contracts the liquid to convert the measured temperature which can be read by a viewer on the calibrated glass tube.



Criteria to choose a Sensor
There are certain features which have to be considered when we choose a sensor. They are as given below:
1.     Accuracy
2.     Environmental condition - usually has limits for temperature/ humidity
3.     Range - Measurement limit of sensor
4.   Calibration - Essential for most of the measuring devices as the readings changes with time
5.     Resolution - Smallest increment detected by the sensor
6.     Cost
7.     Repeatability - The reading that varies is repeatedly measured under the same environment 


Classification of Sensors
The sensors are classified into the following criteria:
1.     Primary Input quantity (Measurand)
2.     Transduction principles (Using physical and chemical effects)
3.     Material and Technology
4.     Property
5.     Application
Transduction principle is the fundamental criteria which are followed for an efficient approach. Usually, material and technology criteria are chosen by the development engineering group.
Classification based on property is as given below:
·        Temperature - Thermistors, thermocouples, RTD’s, IC and many more.
·        Pressure - Fibre optic, vacuum, elastic liquid based manometers, LVDT, electronic.
·        Flow - Electromagnetic, differential pressure, positional displacement, thermal mass, etc.
·        Level Sensors - Differential pressure, ultrasonic radio frequency, radar, thermal displacement, etc.
·        Proximity and displacement - LVDT, photoelectric, capacitive, magnetic, ultrasonic.
·        Biosensors - Resonant mirror, electrochemical, surface Plasmon resonance, Light addressable potentio-metric.  
·        Image - Charge coupled devices, CMOS
·        Gas and chemical - Semiconductor, Infrared, Conductance, Electrochemical.
·        Acceleration - Gyroscopes,     Accelerometers.
·        Others - Moisture, humidity sensor, Speed sensor, mass, Tilt sensor, force, viscosity.
Surface Plasmon resonance and Light addressable potentio-metric from the Bio-sensors group are the new optical technology based sensors. CMOS Image sensors have low resolution as compared to charge coupled devices. CMOS has the advantages of small size, cheap, less power consumption and hence are better substitutes for Charge coupled devices. Accelerometers are independently grouped because of their vital role in future applications like aircraft, automobiles, etc and in fields of videogames, toys, etc. Magnetometers are those sensors which measure magnetic flux intensity B (in units of Tesla or As/m2).
Classification based on Application is as given below:
·        Industrial process control, measurement and automation
·        Non-industrial use – Aircraft, Medical products, Automobiles, Consumer electronics, other type of sensors.
Sensors can be classified based on power or energy supply requirement of the sensors:
·        Active Sensor - Sensors that require power supply are called as Active Sensors. Example: LiDAR (Light detection and ranging), photoconductive cell.
·        Passive Sensor - Sensors that do not require power supply are called as Passive Sensors. Example: Radiometers, film photography.
In the current and future applications, sensors can be classified into groups as follows:
·        Accelerometers - These are based on the Micro Electro Mechanical sensor technology. They are used for patient monitoring which includes pace makers and vehicle dynamic systems.
·        Biosensors - These are based on the electrochemical technology. They are used for food testing, medical care device, water testing, and biological warfare agent detection.
·        Image Sensors - These are based on the CMOS technology. They are used in consumer electronics, biometrics, traffic and security surveillance and PC imaging.
·        Motion Detectors - These are based on the Infra Red, Ultrasonic, and Microwave / radar technology. They are used in videogames and simulations, light activation and security detection. 


Great article

hmm i like it..
hmmm super,i wants more about sensors

Great about sensors.. Time to put this theory into practise
theory into practise..good..please put the by one sensor microcontroller..thanks before..

Thank U For this article

thanks for and all those things


thanks for increase my knowledge

nice one:)


I am little much familiar with sensors and have experience working with IR,SOUND,LDR sensor.

and don't know the mechanism of Smoke sensor. And which kind of sensor are used for car security.

Kindly post about these matters.


thanx and impressive work by site admins...

excellent information   iam satisfied with this

i like thise artical


nice informations ...... great job !!!

22222222 nicee

thnks for the article



simply awesome documents for all


Can proximity sensors be used for counting no.of persons entering and leaving the door??

If not which sensors can be used for such application??

please reply..!! thanks in advance

I would like to reference this article. Where can I find the publication details related to it? ex author, date of publication etc


thanks in advance

i am greatful to be a part of engineersGarage thanks for your support and also thanks for this team........always be so happy and never forget to smile.

can i ask ?

is there any kind of sensor that can detect sudden change on its target



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