Winsen MQ-7B Carbon Monoxide Gas Sensor Module - Semiconductor CO Sensor

The MQ-7B sensor heater requires a dual-voltage cycle for operation. For the low-temperature detection phase, apply approximately 1.5V. For the high-temperature cleaning phase, apply 5.0V. The total heater power consumption is ≤900 mW. You must implement a cycling circuit to switch between these voltages for proper sensor function and longevity.

The MQ-7B outputs a variable resistance. Interface it by placing it in a simple voltage divider circuit with a load resistor, connecting the output to an analog input pin on your Arduino, ESP32, or other microcontroller. You will need to provide the separate heater voltage(s) via a digital output or dedicated driver circuit, cycling them according to the sensor's datasheet for accurate CO measurement.

Yes, like most semiconductor gas sensors, the MQ-7B requires calibration for quantitative measurement. You should establish a baseline resistance in clean air and create a calibration curve using known concentrations of CO gas. Sensitivity can drift over time and is affected by temperature and humidity, so periodic recalibration is recommended for critical applications.

The dual-temperature cycle is crucial for selectivity. At the lower temperature (~1.5V heater), the sensor is sensitive to carbon monoxide. The periodic high-temperature phase (~5.0V heater) burns off other adsorbed gases and contaminants from the SnO2 surface, resetting the sensor and reducing interference from non-target gases, which improves long-term stability and accuracy.