How to Choose an Air Quality or Current Sensor from SparkFun

Updated

Choose by measurement target first: the STCC4/SHT40 CO2 sensor ($30.95) for indoor CO2 plus temperature and humidity, the SFA40 formaldehyde sensor ($49.95) for HCHO from 0–2000 ppb, and the ADE7953-based current sensor ($19.95) or its $28.95 kit for AC current without breaking the circuit. All three use Qwiic I2C, so they suit boards with a Qwiic connector or an I2C bus you can wire manually. Prices and stock are as listed on SparkFun's product pages and can change.

Match the sensor to what you need to measure

Goal Product Listed price Key listed specs
Indoor air quality: actual CO2 concentration SparkFun CO2 Sensor – STCC4/SHT40 (Qwiic) $30.95 (as low as $26.31) Direct CO2 measurement plus temperature and humidity, environmental compensation, Qwiic
Formaldehyde monitoring SparkFun Formaldehyde Sensor – SFA40 (Qwiic) $49.95 (as low as $42.46) HCHO 0–2000 ppb, low cross-sensitivity, built-in environmental compensation, Qwiic I2C
AC current monitoring SparkFun Non-Invasive Current Sensor – ADE7953 (Qwiic) $19.95 (as low as $16.96) Non-invasive AC current measurement, Qwiic-enabled
AC current monitoring, complete setup SparkFun Non-Invasive Current Sensor Kit $28.95 (as low as $24.61) Pairs the ADE7953 sensor with a 100A split-core current transformer

The CO2 and formaldehyde sensors answer "what is in the air"; the current sensors answer "how much power is flowing." They are not substitutes for each other.

Check range and compensation before buying

  • CO2: The page describes direct CO2 measurement with environmental compensation and temperature/humidity monitoring. That matters because CO2 readings drift with temperature and humidity; compensation is built in rather than something you add in software.
  • Formaldehyde: The stated range is 0–2000 ppb with low cross-sensitivity and built-in environmental compensation. If your project only needs a relative trend rather than absolute ppb values, the range still bounds what the sensor can report.
  • Current: The ADE7953 sensor measures AC current non-invasively, meaning you clamp around a conductor instead of cutting the circuit. The kit's 100A split-core transformer sets the upper end of what you can measure; check that your load falls within that range before ordering.

Confirm Qwiic/I2C compatibility with your board

All three products are Qwiic/I2C devices. If your development board has a Qwiic connector, connection is plug-and-play. If not, you need to expose the I2C pins (SDA, SCL, power, ground) and confirm the sensor's logic voltage matches your board — the product pages list the electrical details. Boards without I2C at all are not a fit without an adapter.

Kit versus standalone: pick by what you already own

  • Buy the standalone ADE7953 sensor ($19.95) if you already have a compatible split-core current transformer or want to choose your own.
  • Buy the kit ($28.95) if you want the sensor and the 100A transformer together in one order. The kit is listed as backorder at the time of the page snapshot, while the standalone sensor is in stock — check current availability before deciding.
  • For air quality, there is no kit option listed; the CO2 and formaldehyde sensors are sold as individual Qwiic boards.

Practical checks before checkout

  1. Confirm the measurement target (CO2, HCHO, or AC current) and that the listed range covers your use case.
  2. Verify your board has Qwiic or accessible I2C pins and matching logic voltage.
  3. Check stock status: the CO2, formaldehyde, and standalone current sensors are listed in stock; the current sensor kit is listed as backorder.
  4. Note the quantity discount tiers shown ("as low as" prices) if you are ordering multiple units.
  5. Domestic shipping is free on most orders over $100 per the site banner, which may affect whether you combine items into one order.