This breakout board is a relative humidity and temperature sensor module based on the Silicon Labs Si7021. It’s accessed via I2C interface and it’s very easy to use. The Si7021 comes factory-calibrated, with the calibration values stored on-chip in a non-volatile memory, so it works out of the box with no recalibration procedure.

The Si7021 is highly accurate: the sensor operates over the entire 0-100% RH range and has a typical accuracy of ± 3% over the 0-80% RH range, going towards ± 4.5% when reaching 100% RH. The temperature sensor has a typical accuracy of ±0.4 °C over the -10 to 85°C range.

Inside the Si7021 there is a resistive heating that may be used to raise the temperature of the sensor, to drive off condensation or to test the sensor (as we do in the example for Arduino, links here below).

The board uses the Si7021 version with the factory-fitted protective cover. This hydrophobic/oleophobic cover provides protection during PCB assembly and can be left in place for the lifetime of the product, preventing liquids, dust or other contaminants (particles down to 0.35 microns) to affect the RH readings.

The boards comes fully tested and assembled. Four 0.1″ (2.54mm) spaced pins are exposed providing connections for power supply and I2C communication. The board has 2 solder jumpers to enable the 4K7 pull-ups on the I2C communication lines.

The accuracy and easy of use makes this module perfect for data logging on weather stations or humidity-controlled systems. Check the provided library for Arduino and sample sketch for more insights about the Si7021 usage.


  • 1.9V to 3.6V power supply
  • Accuracy:
    • RH: ± 3% over the 0-80% RH range
    • Temperature: ±0.4 °C over the -10 to 85°C range
  • Resolution
    • 12-bit for RH
    • 14-bit for temperature
  • I2C communication
  • Solder jumper to enable I2C pull-ups
  • Integrated heater
  • Small size
  • Four mounting holes




More Info

Additional information

Weight 0.010 kg
Dimensions 18 × 15 × 2 mm


9 years 4 months ago

Hi to all ,
what is the exact name of the chip? Datasheet (Ordering guide, page 27) describes several version that differ in temperature range and presence of the protective cover.

9 years 4 months ago

The part is Si7021-A10-GM1, –40 to +85 °C operating range, with protective cover.
We’ve update the schematics with the right part number.

9 years 4 months ago

Thanks for the reply. Can I buy a breakout board with Si7021-A10-IM1 chip (industrial temperature range and protective cover)?

9 years 4 months ago

I’m sorry, we already have the boards mounted with the -40 +85 part.


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AK-SI7021 – Humidity and Temperature Sensor

Relative humidity and temperature sensor module based on the Silicon Labs Si7021.


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