A less widely used sensor that nevertheless shows interesting results when monitoring environments over time. Place one in a polythene bag with your hand, or a plant and see how the humidity changes. The range of the sensor varies between manufacturer, and it is within the range 10-90% humidity. Acetone and organic solvent vapours are harmful to the sensor while wetting with water leads to unreliable readings.
My rating ** / +
I’ve rated these sensors but your assessment will be different. I give * to **** for the sensor’s intrigue, interest, and learning potential. I give from + to ++++ for how often a science department might use it.