The ENS161 Gas Sensor is a fully integrated MOX air-quality sensor with I2C/SPI support, delivering eCO₂, TVOC and AQI readings with improved algorithms — ideal for Arduino, Raspberry Pi and STEMMA QT projects.
Sniff, sniff… smell that? Instead of checking a carton of milk, you can build your own digital nose with the ENS161 Gas Sensor. It’s a fully integrated MOX gas sensor from air-quality specialists ScioSense, designed to make gas sensing far easier than traditional MOX setups. With I2C (and SPI) support, you don’t have to manage heater control or analogue readings yourself. Multiple metal-oxide sensing and heating elements are combined on a single chip to deliver more detailed air quality information.
The ENS161 is the successor to the ENS160, which itself replaced the now-discontinued CCS811. It keeps the same four-element gas sensor design and digital interface, but adds improved eCO₂ and TVOC algorithms, along with a new Air Quality Index (AQI) output.
At its core, the ENS161 uses a standard hot-plate MOX sensor divided into four sections, paired with a small onboard microcontroller. This handles heater power, reads analogue voltages, and exposes everything through a digital interface. ScioSense provides an Arduino library with examples for reading raw resistance values, TVOC and eCO₂, as well as Python and CircuitPython libraries for Linux systems like the Raspberry Pi and CircuitPython-based boards.
As with all VOC and gas sensors, readings can vary, so calibration against known sources is recommended if you need precise measurements. For general environmental monitoring, though, it’s very useful for spotting trends and making comparisons.
One handy feature is support for temperature and humidity compensation, which helps improve accuracy. This requires an external humidity sensor, with RH values sent to the ENS161 over I2C so it can compensate for environmental effects on the MOX readings.
To make getting started easy, the surface-mount ENS161 is pre-soldered onto a custom PCB in the STEMMA QT form factor. Connectors on both sides are compatible with SparkFun Qwiic, allowing quick, solder-free connections or easy daisy-chaining with other sensors (note: cable not included).
All pins are also broken out to standard headers, and the board includes a 3.3V regulator and level shifting, so it works with both 3.3V and 5V systems, including boards like the Arduino Uno and Feather M4.
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