Introduction to Gas Sensor

A gas sensor may be a device that detects the presence or concentration of gases within the atmosphere. supported the concentration of the gas the sensor produces a corresponding electric potential by changing the resistance of the fabric inside the sensor, which may be measured as output voltage. supported this voltage value the sort and concentration of the gas are often estimated. 

The type of gas the sensor could detect depends on the sensing material present inside the sensor. Normally these sensors are available as modules with comparators as shown above. These comparators are often set for a specific threshold value of gas concentration. When the concentration of the gas exceeds this threshold the digital pin goes high. The analog pin is often wont to measure the concentration of the gas.

Different Types of Gas sensors

Gas sensors are typically classified into various types based on the type of sensing element it is built with. Below is the classification of the various types of gas sensors based on the sensing element that is generally used in various applications:

  • Optical gas Sensor.
  • Calorimetric gas Sensor.
  • Acoustic based gas Sensor.
  • Electrochemical gas Sensor.
  • Capacitance-based gas Sensor.
  • Metal Oxide-based gas Sensor.

Pinout of MQ-2 gas sensor

Pin out of MQ-2 gas sensor is given below:

  • Connect Vcc: 5v power supply
  • Ground: Ground pin of power supply
  • Aout:  Analog pin of pic microcontroller

How does it Work?

The voltage that the sensor outputs changes accordingly to the smoke/gas level that exists in the atmosphere. The sensor outputs a voltage that is proportional to the concentration of smoke/gas.

In other words, the relationship between voltage and gas concentration is the following:


  • Working Voltage: 4.9-5.1V
  • Heating consumption: 0.5-800mW
  • Load resistance: can adjust
  • Heater resistance: 33Ω
  • Sensing Resistance: 3-30kΩ
  • Working Temperature: -25~70 ℃

Gas Sensor

The Grove – Gas Sensor module is useful for gas leakage detecting(in home and industry). It can detect LPG, i-butane, methane, alcohol, Hydrogen, smoke and so on. Measurements can be taken as soon as possible based on its fast response time. Also, the sensitivity can be adjusted by the potentiometer.

Each Grove – Gas Sensor Kit consists of one gas sensor base and four detectors. You can switch the detector on the base according to specific target gases.

  • Grove – Gas Sensor(MQ2):Combustible Gas, Smoke
  • Grove – Gas Sensor(MQ3):Alcohol Vapor
  • Grove – Gas Sensor(MQ5):LPG, Natural Gas, Town Gas
  • Grove – Gas Sensor(MQ9):Carbon Monoxide, Coal Gas, Liquefied Gas