Adafruit HDC3021 Precision Temperature & Humidity Sensor - STEMMA QT / Qwiic

Adafruit stock a large number of Temperature/Humidity sensors, so you're probably wondering why another one? Well, this Adafruit HDC3021 Precision Temperature & Humidity Sensor breakout features the highest accuracy & precision one Adafruit have see so far! It has the TI HDC302x series chip with typical 0.5% accuracy for the RH sensor (with 0.19% long-term drift) and ±0.1°C typical accuracy for the temperature sensor. All at a very nice price.

This sensor has a true I2C interface for easy interfacing with only two wires (plus power and ground!). That makes it preferable to the janky DHT11/DHT22 sensors. The sensor is 5V safe, so you can use 1.8V to 5V power and logic levels without the need for shifters, so you can power and communicate with it using any microcontroller or microcomputer. With 4 selectable I2C addresses, you can have multiple sensors on one bus - unlike many other fixed-address T/RH sensors.

Adafruit have written a full-featured Arduino and CircuitPython/Python library, so whether you have an 8-bit microcontroller or a quad-core Raspberry Pi, you will be able to quickly get data from the sensor for your environmental monitoring needs. The library can setup the sensor rate/power, heater, alerts, offsets, and read data or NIST tracking ID.

Such a lovely chip - so they spun up a breakout board with the HDC3021 and some supporting circuitry such as pullup resistors and capacitors. To make things even easier, Adafruit have included SparkFun Qwiic compatible STEMMA QT connectors for the I2C bus so you don't even need to solder! QT Cable is not included, but Adafruit have a variety in the shop. 

If you prefer working on a breadboard, each order comes with one fully assembled and tested PCB breakout and a small piece of header. You'll need to solder the header onto the PCB, but it's fairly easy and takes only a few minutes even for a beginner. 

Please note: this sensor comes with a protective polyamide sticker on top, please remove before usage!

Technical Details

HDC302x specifications:

• Relative humidity (RH) sensor:– Operating range: 0% to 100%– Accuracy: ±0.5% typical– Offset Error Correction: reduces offset to return device to within accuracy specification– Long-term drift: 0.19%RH/yr– Condensation protection with integrated heater
•  Temperature sensor:– Operating range: –40°C to 125°C– Accuracy: ±0.1°C typical
• NIST traceability: relative humidity & temperature
• Low power: average current 0.4 µA (sensor only, not including on-board green LED which can be disabled)
• I2C interface compatibility up to 1-MHz speeds– Four selectable I2C addresses– Data protection through CRC checksum
• Supply voltage: 1.62 V to 5.50 V
• Available auto measurement mode
• Programmable interrupts
• Programmable RH and Temp measurement offset

Product Dimensions: 25.4mm x 17.7mm x 4.7mm / 1.0" x 0.7" x 0.2"

Product Weight: 1.6g / 0.1oz