What Is a Humidity Sensor?
A humidity sensor is a sensor that measures the amount of water vapor in the air, i.e. the relative humidity (%RH). Most modern types also measure temperature.
How Does It Work?
The most common type is capacitive: the capacitance of a moisture-sensitive material changes with humidity. Simpler types are resistive, with a resistance that changes with humidity.
Types
| Type | Property |
|---|---|
| Capacitive | Precise, stable (e.g. SHT, BME280) |
| Resistive | Cheap, simple (e.g. DHT11) |
Where Is It Used?
Weather stations, greenhouse and warehouse monitoring, air-conditioning/dehumidifiers and smart-home systems.
Dew Point
Most humidity sensors also measure temperature at the same time, because relative humidity depends on temperature. From the two, the dew point (the temperature at which condensation begins) can be calculated — very useful for foreseeing the risk of mold and condensation.
Common Mistakes
- Condensation: water droplets forming can damage the sensor temporarily/permanently.
- Expecting a slow response: humidity measurement lags on sudden changes.
- Calibration drift: cheap types can drift over time.
Frequently Asked Questions
What's the difference between DHT11 and DHT22?+
What does relative humidity mean?+
Search parts related to "What Is a Humidity Sensor?"
Find the right part by comparing price, stock and distributors.