SparkFun CO₂ Humidity and Temperature Sensor - SCD40 (Qwiic)

Jargon buster

Plain-language definitions for the technical terms used above.

Automatic Self-Calibration

Automatic Self-Calibration is a built-in routine that adjusts the sensor over time to reduce drift in its readings. It matters for long-running indoor monitors because it can help keep measurements stable without frequent manual calibration.

breakout

A breakout is a small circuit board that makes a tiny or hard-to-solder component easier to connect to with standard pins. It matters because this OLED module can be wired into a microcontroller project without needing to solder directly to the display’s fine contacts.

CMOSens

CMOSens is Sensirion’s integrated sensor technology that combines sensing elements and electronics in one package. It matters because it affects how the sensor measures temperature and humidity and how it is supported by the manufacturer’s libraries and datasheets.

I2C

I2C is a two-wire communication bus used by many sensors and small modules. It matters because several I2C devices can share the same two wires, but each device needs a compatible address and your controller must support I2C.

PASens

PASens is Sensirion’s name for its photoacoustic sensing technology used in some CO2 sensors. Knowing this helps explain why the sensor uses light and a microphone internally rather than a simple chemical gas sensor.

photoacoustic measurement

Photoacoustic measurement detects gas by shining light into a sample and listening for tiny pressure waves created when the gas absorbs that light. In a CO2 sensor, this matters because it is the method used to estimate carbon dioxide concentration.

ppm

ppm means parts per million, a common way to express very small gas concentrations in air. For CO₂ sensors, the ppm range tells you what levels the sensor can measure, such as normal indoor air through to poorly ventilated spaces.

Qwiic

Qwiic is a plug-in connector system for I2C devices that uses small 4-pin cables, so you can connect compatible sensors without soldering. It matters because your controller or adapter also needs Qwiic, or you will need a cable or breakout to wire it up.