Which property is used by humidity sensors to determine moisture levels in materials?

• A. Physical and electrical properties
• B. Humidity levels
• C. Temperature
• D. Color

Answer: (A)

Moisture sensors detect humidity by watching how water alters the physical and electrical properties of the sensing material. When moisture is present, water molecules interact with the hygroscopic layer, changing its dielectric constant and its ability to conduct electricity. In capacitive sensors, this shows up as a change in capacitance because the dielectric constant increases with more moisture. In resistive sensors, moisture boosts ionic conduction or causes material swelling, lowering the resistance and producing a signal proportional to humidity. Temperature can affect readings since it also changes material properties, but it’s not the property used to sense moisture itself. Color isn’t involved in these measurements. The essential idea is that moisture changes the physical/electrical properties of the sensing material, and those changes reveal the humidity level.