To learn more about how thermistors work and how to use them on the Arduino, check out our Arduino Thermistor Temperature Sensor Tutorial. The DHT11 measures temperature with a surface mounted NTC temperature sensor (thermistor) built into the unit. Higher relative humidity decreases the resistance between the electrodes, while lower relative humidity increases the resistance between the electrodes. The change in resistance between the two electrodes is proportional to the relative humidity. When water vapor is absorbed by the substrate, ions are released by the substrate which increases the conductivity between the electrodes. The DHT11 detects water vapor by measuring the electrical resistance between two electrodes. The humidity sensing component is a moisture holding substrate with electrodes applied to the surface. How the DHT11 Measures Humidity and Temperature At 100% RH, condensation occurs, and at 0% RH, the air is completely dry. Relative humidity is expressed as a percentage. The formula to calculate relative humidity is: Cold air can hold less water vapor before it becomes saturated, and hot air can hold more water vapor before it becomes saturated. The saturation point changes with air temperature.
At the saturation point, water vapor starts to condense and accumulate on surfaces forming dew. the saturation point of water vapor in air. Relative humidity is the amount of water vapor in air vs. Here are the ranges and accuracy of the DHT11:ĭHT11 Datasheet What is Relative Humidity? It includes all of the parts, wiring diagrams, code, and step-by-step instructions for 58 different robotics and internet of things projects that are super fun to build! The 3-in-1 Smart Car and IOT Learning Kit from SunFounder has everything you need to learn how to master the Arduino.
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