The Adafruit AS7331 UV Sensor measures UVA, UVB, and UVC separately, giving you detailed UV data over I2C for everything from environmental monitoring to specialised applications.
The Adafruit AS7331 UVA / UVB / UVC Sensor Breakout is a flexible UV sensor that can measure and distinguish between all three ultraviolet bands, making it suitable for a wide range of monitoring and detection applications.
Unlike most UV sensors that only measure UVA (and sometimes ambient light), the AS7331 provides separate readings for UVA, UVB, and UVC. This makes it useful for everything from human and agricultural UV monitoring (typically focused on UVA and UVB) to more specialised uses such as germicidal, curing, and industrial UVC applications. Each band is measured independently rather than combined into a single value, giving you more meaningful data.
The sensor features configurable gain and conversion settings over I2C, allowing for a wide measurement range. At 1× gain, it can measure up to 349 mW/cm² on the UVA channel, 386 mW/cm² on UVB, and 169 mW/cm² on UVC, with sensitivity down to 2.38 nW/cm² per LSB.
Alongside the standard I2C interface, the board includes options for more advanced control. The default I2C address (0x74) can be changed using two jumpers on the back, allowing up to four sensors on the same bus. There’s also a READY pin to indicate when a conversion is complete, and a SYNC input for synchronising measurements with an external signal.
The sensor is mounted on a STEMMA QT breakout with built-in level shifting and Qwiic-compatible connectors, making it easy to connect to both 3.3V and 5V systems without soldering. It works with platforms such as Arduino, Raspberry Pi, and CircuitPython-compatible boards.
To help you get started, Adafruit provides Arduino and CircuitPython libraries with example code for configuring and reading the sensor over I2C. The QT Cable is not included, but we offer a range of options here.
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