MQ137 Ammonia gas sensor

The gas sensing material used in the MQ137 ammonia gas sensor is tin dioxide (SnO2), which has a low conductivity in clean air. When there is ammonia gas in the environment where the sensor is located, the conductivity of the sensor increases with the increase of the ammonia gas concentration in the air. The change in conductivity can be converted into an output signal corresponding to the gas concentration using a simple circuit.

The MQ137 ammonia gas sensor has high sensitivity to ammonia gas, and is also ideal for monitoring other organic amines (such as trimethylamine, ethanolamine, etc.). This sensor can detect a variety of ammonia-containing gases and is a low-cost sensor suitable for a variety of applications.


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Sensor Features
High sensitivity to ammonia gas

Long life and low cost

A simple drive circuit can


main application
Home use ammonia gas alarm

Industrial ammonia leak alarm

Portable Gas Detector


Technical indicators

Product number

MQ137 Ammonia gas sensor

product type

Semiconductor gas sensor

standard package

bakelite, metal cover

detect gas


Detection concentration

5-500ppm ammonia gas

Standard Circuit Conditions

loop voltage


≤24V  DC

heating voltage


5.0V±0.1V ACorDC

Load Resistance



Gas sensor characteristics under standard test conditions

heating resistance


29Ω±3Ω(room temperature)

Heating power consumption



The output voltage


≥0.5V(in 50ppm NH3)



Rs(in air)/Rs(50ppmNH3)≥2

Concentration slope


≤0.6(R200ppm/R50ppm NH3)

Standard Test Conditions

temperature humidity


Standard Test Circuit


 VH: 5.0V±0.1V

Preheat time

Not less than 48 hours

oxygen content

21% (not less than 18%, the oxygen concentration will affect the initial value, sensitivity and repeatability of the sensor, please consult when using it under low oxygen concentration)


5 years

Note: The output voltage (Vs) refers to the VRL in the test atmosphere

production workshop


patent certificate

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