Gas sensor

Hello geeks in this article I am going to share information about the various gas sensors and also their working principle. There is a very interesting phenomena in working of gas sensor I will share that information with some illustrations in this article.

First of all we get a doubt what is a gas sensor, why we need it?

What is working principle behind it ?

What are the different gas sensor and where do we use them ?

Dont worry, I am going to answer all these questions in this article.

Our first question is very simple to answer a gas sensor is a device that senses the gas around it and gives us the output either in a digital signal for a continuous discrete values as a analog signal.

When when we come to the next question why we need it then the reason is to identify the gas leakage in the home, industries, hotels and they are also used for detecting the alcoholic people. It is used to detect the flammable,  toxic gases in petroleum and some other industries. They are also need in mining areas.

External appearance :

A typical gas sensor consists of a semiconductor material enclosed in a mesh like material to prevent the contact of unwanted dust particles with the sensitive semi conductor material as shown in the below figure.

Gas sensor

It consists of a six pins they are namely two H pins in the middle and the remaining are pair of A pins on either side and like wise two B pins as shown in the below figure

                  2,5 are H pins                       

                  1,3 are A pins

                  6,4 are B pins


Now when we come to the pins connected to the module there are four pins and namely they are

1. Vcc

2. Digital signal pin.

3. Analog signal pin.

4. Ground pin.


Working principle :

A simple gas sensor is made up of semiconductor material which is very sensitive and it is SnO2. The conductivity of this material changes the concentration of the gas present around it. Higher the gas content present , higher is the conductivity of that material. the circuit diagram is very simple to understand and it is like below

Voltage is applied to the heater that initiate the semiconductor to work when the voltage across the A and B pins vary according to the gas content due it’s conductivity and it is treated as a output signal.

For the better performance two pairs of A and B pins are used and these pins are interchangeable as the material is simply resistor and it is bilateral element.

Voltage fluctuations at A and B pins  act as a signal data line to microprocessor and help us to draw the outputs.

 That is the simple principle behind the working of the gas sensor.



Now I will discuss about the various gas sensors. There are many gas sensors in the MQ series with names MQxx starting from 2 to 10 and each have its significant use and purpose

  • MQ-2 is for detecting General combustible gas
Gas sensor


  • MQ-3 is for detecting the Alcohol .
Gas sensor


  • MQ-4 is for detecting Natural gas, Methane
  • MQ-5 is for detecting LPG, Natural gas, Coal gas
  • MQ-6  is for detecting LPG, Propane
  • MQ-7 is for detecting Carbon Monoxide
  • MQ135 is for detecting Air Quality  Control
Gas sensor

Still there are many more models present in market .

I think with this article you could understand the principle behind the working of a gas sensor and basics of it. For any queries the comment box below is always open for you. I will be back with new interesting information once again

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