MQ-137 NH3 Ammonia Gas Sensor Module

The MQ-137 module requires a stable 5V DC power supply for both the sensor heater and the onboard circuitry. Operating outside this voltage, especially with higher voltages, can damage the sensor element and the comparator circuit.

The module provides two outputs. The analog output (A0) gives a voltage between 0V and 5V proportional to the ammonia concentration. The digital output (D0) provides a TTL signal (0V or 5V); it goes LOW (0V) when the gas concentration exceeds the threshold set by the onboard potentiometer. Both can be read by a microcontroller like Arduino.

Yes, like most metal oxide semiconductor (MOS) gas sensors, the MQ-137 requires a pre-heating period, typically 1-2 minutes after applying power, to stabilize the sensing element's temperature. For consistent baseline readings, a longer pre-heat of 24-48 hours is recommended for critical applications.

Yes, the digital output's trigger point is adjustable. Use a small screwdriver to turn the onboard blue potentiometer. Clockwise rotation generally increases sensitivity (triggers at lower gas concentrations), while counter-clockwise rotation decreases it.

The MQ-137 is specifically optimized for detecting ammonia (NH3) gas. While it may show some cross-sensitivity to other reducing gases, its sensing material and calibration are primarily targeted for accurate NH3 measurement within its 5-500 ppm range.