Gas sensing techniques are continually being investigated to improve selectivity and sensitivity of identifying different types of gases. There are resistive gas sensors, quartz crystal microbalance, direct thermoelectric, electrochemical cell and other exotic types such as MEMS-tunable Fabry-Perot filter spectral sensors with lead-selenide detector and pulsed broadband infrared emitter light source. The ams sensor is a resistive type.
The resistive sensor design relies upon heating circuitry for temperature control of the entire system. There are different types of resistive gas sensor techniques and construction. Some are based upon metal-oxide (MOX) thin films which are small in size, low-cost, and low power as well as able to use low-power integrated analog front ends.
The gas sensor
The ams sensor is accurate, small and power efficient which produces a precisely varying resistance as the ambient level of pollutants changes. The sensor’s accurate VOC detection capability results from the implementation of proprietary MEMS and metal oxide semiconductor (MOS) technology developed by ams. The sensor is available in a surface-mount package and in a small footprint and offers long-term stable operation, while only consuming a low amount of power (typically 34mW in continuous operation).
The AS-MLV-P2 sensor component chips are fabricated using silicon technology. The platinum heater (Operating at 320o C) and inter-digital electrode structures are placed on an approximately one micrometer-thin LPCVD silicon nitride membrane to achieve the lowest possible power consumption. A highly reproducible tin dioxide-based sensitive layer is deposited over the inter-digital electrodes, forming a gas concentration dependent conductivity. AS-MLV-P2 is reflow capable and can be connected via edge connectors.
For More Details: ams develops MEMS VOC gas sensor