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WSAL11092 – DHT22 Temperature-Humidity Sensor/en

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Documentation notice: This technical documentation was independently rewritten from an archived supplier source. Check technical details and commands against the product version and manufacturer documentation before use.

Summary

Calibrated digital temperature and humidity module (AM2302) for measuring ambient temperature and humidity via a single-wire interface.

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Technical overview

  • Sensor: DHT22 (AM2302); calibrated digital module with higher accuracy and wider range than the DHT11.
  • Temperature resolution 0.1 °C; accuracy ±0.5 °C; range −40 °C to 80 °C.
  • Humidity resolution 0.1 %RH; accuracy ±2 %RH at 25 °C; range 0 %RH to 99.9 %RH.
  • Operating voltage: 3.3 V to 5.5 V.
  • Recommended storage conditions: 10 °C to 40 °C, humidity ≤ 60 %RH.
  • Pins: Pin 1 = VCC (power), Pin 2 = GND, Pin 3 = DOUT (SDA data line of the AM2302).
  • Communication uses a simplified single-bus protocol; in idle state the bus line is pulled HIGH by an external pull-up resistor of about 5.1 kΩ.
  • One transmission carries 40 bits, MSB first: humidity high/low, temperature high/low, parity bit.
  • Start signal: host pulls SDA low for at least 800 µs; the sensor responds with 80 µs LOW followed by 80 µs HIGH.
  • After the start signal the sensor transmits 40 bits serially; the parity bit equals the sum of the four data words modulo 2.

Notes and version constraints

  • The source contains no explicit commands or API calls for the DHT22; concrete code examples are not included in the provided text.
  • Accuracy specifications apply only under the stated reference conditions (e.g., ±2 %RH at 25 °C); deviations at other temperatures are expected.
  • The single-bus timing (800 µs start, 80 µs response, 50/70 µs bit encoding) is version-sensitive; changes to the sensor firmware may alter the protocol.
  • Storage conditions (10–40 °C, ≤60 %RH) are recommended values, not guarantees; prolonged storage outside this range may affect calibration.

Source and revision record

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