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High-sensitivity MEMS carbon monoxide gas sensor supporting a concentration range of 5 to 5000 ppm CO. Operating at low power consumption of just 50mW, it is ideal for portable or embedded devices. The sensor's heating voltage can be switched between high-temperature and low-temperature modes, offering flexible adaptation for applications ranging from home air detectors to industrial alarm systems.
Description: The figure above shows the basic test circuit for a MEMS carbon monoxide sensor. This sensor requires two applied voltages: Heater voltage (VH) and test voltage (VC). VH is used to provide the sensor with a specific operating temperature and can be supplied by either a DC or AC power source. Vout is the voltage across the series load resistor (RL) of the sensor. VC is the test voltage applied to the load resistor RL and must be supplied by a DC power source.
The carbon monoxide gas sensor utilizes MEMS technology to fabricate a microheater on a silicon substrate. The gas-sensitive material employed is a metal oxide semiconductor with low electrical conductivity in clean air. When the target gas is present in the ambient air, the sensor's conductivity changes. Higher concentrations of carbon monoxide result in higher sensor conductivity. A simple circuit converts this conductivity change into an output signal proportional to the gas concentration.
The accuracy of CO sensors is influenced by factors such as variations in reference resistance between sensors, sensitivity differences, temperature, humidity, interfering gases, and aging time. Their input-output relationship exhibits nonlinearity, hysteresis, and non-repeatability in operational characteristics. Therefore, periodic calibration (single-point/multi-point calibration across the full range is possible) is essential for absolute concentration measurements to ensure accurate value transfer of the CO sensor. Relative measurements do not require calibration.
When MEMS gas sensors are stored for extended periods without power, their resistance undergoes reversible drift. Preheating is required before use to achieve internal chemical equilibrium. The warm-up voltage must match the heating voltage VH.