Environmental monitoring using smart air quality sensors is expanding across various applications from smart homes, buildings, and cities, to conventional and electric vehicles (EVs) and battery energy storage systems (BESS). In smart homes, buildings, and cities, air quality sensors can help ensure health and safety by monitoring airborne particles and gases associated with poor air quality, as well as smoke detection for early fire warnings. In vehicle passenger compartments, these sensors can identify volatile organic compounds (VOCs) and high levels of CO2 that can raise health concerns. In EVs and BESS, they can be used to detect an increase in pressure and high levels of hydrogen in a battery enclosure following the first venting phase of a cell, enabling the battery management system (BMS) to react and prevent a second venting event or thermal runaway of the whole battery system. The sensors used in these applications need to be compact, low power, and able to support secure boot and secure firmware updates. They often need to include multiple sensors, covering a broad spectrum of air quality monitoring. Integrating this range of functionality in a compact and low-power unit can be a daunting process, prone to restarts, resulting in a high-cost solution and delaying time to market.
To speed time to market and control costs, designers can turn to sensor modules that are factory calibrated, support secure boot and firmware updates, and provide connectivity options, including sending data to the cloud or using a CAN or other bus for local connections. This article begins by comparing optical particulate counters, screen-printed electrochemical, and multi-parameter sensor technologies. It presents air quality sensor solutions and development platforms from Sensirion, Metis Engineering, and Spec Sensors, along with companion devices from Infineon Technologies, and includes suggestions to speed the development process.
Particulate matter (PM) sensors provide counts for specific particle sizes such as PM2.5 and PM10, which correspond to particles with diameters of 2.5 microns and 10 microns, respectively, as well as other particle sizes as needed by the specific application. Optical particle counters (OPCs) are a specific PM technology that moves the air to be measured through a measurement cell that contains a laser and a photodetector (Figure 1). Particles in the air scatter the light from the laser, and the detector measures the scattered light. The measurement is converted into mass concentration in micrograms per cubic meter (μg/m3) and counts the number of particles per cubic centimeter (cm3). Counting particles using an OPC is straightforward but converting that information into
Figure 1: An OPC uses a laser and photodiode to count airborne particles. (Image source: Sensirion)
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