An Overview about MQ137 Sensor
The MQ137 is basically an Ammonia (NH₃) gas sensor. The sensor includes tin dioxide as its sensing element. The SnO2 (tin dioxide)has lower conductivity in pure air. When the air has ammonia, the conductivity of the sensor gets higher. A simple device makes measuring this change in conductivity and turning it into obvious data. However, the sensor requires some calibration.
Hardware
The MQ137 comes either in sensor or module form. If you have picked up the module already, now you have to perform a little hack. So, join one end of H to the supply, and the other end of that H, you need to connect it to the ground. Then you need to connect both A’s and both B’s. And, from those sets, you need to connect one set to the supply voltage and connect the other set to your analog pin. The resistor RL plays a very influential role in making the sensor performance. So, make an observation of what value you are using.
Working Principle
When there is NH3 gas around, the conductivity of the sensor gets stronger along with the gas concentration rising. Now, we can convert the change of conductivity to correspond output signal of gas concentration using a microcontroller.
Features and Specifications of MQ137 Sensor
There are many prominent features and specification of MQ-137 which makes it more extraordinary
Features
- Good sensitivity to NH3 gas in a wide range.
- Long lifespan.
- Low cost
- Simple drive circuit
- Can be used as a Digital or analog sensor
- We can vary the Sensitivity of Digital pin using the potentiometer
Specifications
- Operating Voltage is +5V
- Can be used to Measure Ammonia, Carbon monoxide
- Analog output voltage: 0V to 5V
- Digital Output Voltage: 0V or 5V (TTL Logic)
- Preheat duration over 24 hours
Pinout of MQ137
| Pin Number | Pin Name | Description |
| 1 | Vcc | The [in is there to power the module, requires 5V |
| 2 | Ground | To connect the module to the system’s common ground |
| 3 | Digital Out | Digital output pin, the Threshold value can be set by using the potentiometer |
| 4 | Analog Out | Analog output pin. Analog voltage based on the concentration of the gas |
Applications of MQ137 Sensor
Ammonia or Carbon Monoxide Detection
Using this system, we can immediately collect information about ammonia, carbon monoxide, and can also display the level of gases that can be handled by any microcontroller.
Air Quality Monitoring
Air quality monitoring provides an acceptable monitoring method that uses an MQ137 sensor. This is a lightweight, customer-friendly, and low-cost air monitoring device that can measure the different levels of harmful gases, therefore we can use this anywhere.
Gas Leak Alarm
The objective of detecting a gas leak is to prevent the worst potential causes of the gas leak, using the above-mentioned type of MQ sensor. The choice of the MQ137 sensor is because of the nature of MQ137 which is suitable for detecting ammonia and other gases
