Open Air Outdoor Air Quality Monitor - Humidity readings are off


I’ve place three different monitors in the same room to compare the measures:

  • an airgradient outdoor DIY monitor
  • an airgradient indoor DIY Pro monitor
  • and an amazon monitor

All monitors measures are close except for the relative humidity returned by the outdoor monitor. It’s off by about 25% compared to what the other two return.

Is there some kind of calibration that I can do ?



Edit: wording

The raw humidity readings from the plantower PMS5003T are off by around 20-25%.

You can use the following correction formula:

Humidity Compendated = 1.3921 * Humidity from sensor - 1.0245
Example: 57.44 = 1.3921 * 42 - 1.0245

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I’ve just applied these factors to my Open Air device and the resulting humidity readings appear to be correct, so thanks for that!

I wonder why the factors in this post are different from the ones in the blog post on the same topic?

The correction formulas are based on different data sets with different ranges of humidity. We are still collecting data and will come up with improved algorithms over time.