DHT22 (AM2302) Digital Temperature and Humidity Sensor

• Power supply 3.3-6V DC
• Output signal –  digital signal via single-bus
• Sensing element Polymer capacitor
• Operating range humidity 0-100%RH; temperature -40~80Celsius
• Accuracy humidity +-2%RH(Max +-5%RH); temperature <+-0.5Celsius
• Resolution or sensitivity humidity 0.1%RH; temperature 0.1Celsius
• Repeatability humidity +-1%RH; temperature +-0.2Celsius
• Humidity hysteresis +-0.3%RH
• Long-term Stability +-0.5%RH/year
• Sensing period Average: 2s
• Interchangeability fully interchangeable
• Dimensions small size 15.1x25x7.

Note: DHT22 (AM2302) Digital Temperature and Humidity Sensor supplied with wire

(DHT22 also named as AM2302)

Every sensor of DHT22 (AM2302) Digital Temperature and Humidity Sensor is temperature compensated and calibrated in an accurate calibration chamber and the calibration-coefficient is saved in the type of programme in OTP memory when the sensor is detecting, it will cite coefficient from memory.
Small size & low consumption & long transmission distance (20m) enable DHT22 to be suited in all kinds of harsh application occasions.

Temperature Sensor Types

• Negative Temperature Coefficient (NTC) thermistor

A thermistor is a thermally sensitive resistor that exhibits a continuous, small, incremental change in resistance correlated to variations in temperature. An NTC thermistor provides higher resistance at low temperatures. As temperature increases, the resistance drops incrementally, according to its R-T table. Small changes reflect accurately due to large changes in resistance per °C. The output of an NTC thermistor is non-linear due to its exponential nature; however, it can be linearized based on its application. The effective operating range is -50 to 250 °C for glass encapsulated thermistors or 150°C for standard Thermistors.

• Resistance Temperature Detector (RTD)

A resistance temperature detector, or RTD, changes the resistance of the RTD element with temperature. An RTD consists of a film or, for greater accuracy, a wire wrapped around a ceramic or glass core. Platinum makes up the most accurate RTDs while nickel and copper make RTDs that are lower cost; however, nickel and copper are not as stable or repeatable as platinum. Platinum RTDs offer a highly accurate linear output across -200 to 600 °C but are much more expensive than copper or nickel.

• Thermocouples

A thermocouple consists of two wires of different metals electrically bonded at two points. The varying voltage created between these two dissimilar metals reflects proportional changes in temperature. Thermocouples are nonlinear and require a conversion with a table when used for temperature control and compensation, typically accomplished using a lookup table. Accuracy is low, from 0.5 °C to 5 °C but thermocouples operate across the widest temperature range, from -200 °C to 1750 °C.

• Semiconductor-based temperature sensors

A semiconductor-based temperature sensor is usually incorporated into integrated circuits (ICs). These sensors utilize two identical diodes with temperature-sensitive voltage vs current characteristics that are used to monitor changes in temperature. They offer a linear response but have the lowest accuracy of the basic sensor types. These temperature sensors also have the slowest responsiveness across the narrowest temperature range (-70 °C to 150 °C).

Development  Resources: demo codes, schematics, datasheets, etc

Reference for Arduino and reference to all matters

Ardunio from Wikipedia

Notes:

1. There may be slight size deviations due to manual measurement, different measuring methods and tools.
2. The picture may not reflect the actual colour of the item because of different photographing light, angle and display monitor.

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