MQ-9 gas sensor - carbon monoxide and flammable gases, 5 V

Product overview

• Sensor for carbon monoxide and combustible gases with analog output signal
• Measuring range: 10 to 1000 ppm for CO, 100 to 10000 ppm for combustible gases
• Operating voltage: 5 V, current consumption approximately 150 mA
• Analog output: 0 to 5 V via RL resistor (typically 10 kOhm)
• Warm-up time approximately 20 seconds, calibration in fresh air required
• Semiconductor detector with heating element, long service life without wear parts

Product description

The sensor detects carbon monoxide in the air as well as combustible gases and outputs the concentration as a voltage signal. Within approximately 20 seconds after switching on, the sensing element reaches its operating temperature. The output signal is then 0 to 5 volts, with higher voltages indicating higher gas concentrations.

The detector uses a semiconductor element whose conductivity changes when it comes into contact with gases. An integrated heating element keeps the sensing point at a constant temperature. Since no chemical reactants are consumed, regular sensor replacement is not required. The output signal is adjusted via an external load resistor (approximately 10 kOhm) and can be connected directly to analog-to-digital converters of microcontrollers or single-board computers.

The sensor is suitable for warning devices in garages and workshops, portable CO detectors, monitoring in ventilation systems, or laboratory measurements during the development of fuel-powered prototypes. In environments containing other gases or vapors, the measured values may be affected; therefore, the application must be adapted to the specific use case.

The sensor requires a stable 5 V power supply with sufficient current capacity. Before the first measurement, it must be calibrated in fresh air by recording the output voltage value under known air-quality conditions. The measured values are not linear across the entire range but follow a logarithmic characteristic curve, so a characteristic-curve table or calibration procedure is required.

Safety notice

The sensor is intended exclusively for building prototypes and for testing and development purposes and is not suitable as a replacement for approved gas detection systems. For measurement tasks that affect personal safety, the determined values must be checked by a qualified electrician. The sensor is not intended for direct installation in household electrical circuits.

Scope of delivery

• 1x MQ-9 - sensor for carbon monoxide and combustible gases