The AM2302 (DHT22) is a high-precision, low-cost digital temperature and humidity composite sensor. Built around a capacitive polymer humidity sensing element and an NTC temperature measurement element connected to a high-performance 8-bit microcontroller, it outputs a pre-calibrated digital signal containing precise environmental data. It offers superior accuracy, faster response times, and wider measurement ranges compared to basic sensors, making it ideal for environmental logging, automated climate control, and smart agriculture.

Specifications

• Sensor Chip: AM2302 (DHT22)
• Working Voltage: 3V to 5.5V DC
• Sensing Elements: Polymer humidity capacitor & NTC temperature sensor
• Temperature Measurement Range: -40°C to +80°C
• Temperature Measurement Error: ±0.5°C (max ±1°C)
• Humidity Measurement Range: 0% to 99.9% RH (in 0°C to 50°C range)
• Humidity Measurement Error: ±2% RH
• Resolution: 16-bit
• Sampling Period: 2 seconds (0.5 Hz)
• Output Signal: Single-bus digital interface (40 bits per transmission, MSB first)
• Calibration: Factory-calibrated with coefficients stored in internal OTP memory

Interface and Pinout Guide

(Note: Standalone AM2302 sensor packages feature 4 pins, while module breakout boards usually break out 3 pins)

• VCC (Pin 1): Power Supply Input (3V to 5.5V DC)
• SDA / DATA (Pin 2): Single-bus Digital Data Line (Sends 40 bits of data per readout to MCU)
• NC (Pin 3): No Connection / Unused pin (Present on 4-pin packages)
• GND (Pin 4): Common Power and Signal Ground Reference

Key Features

• Factory Calibrated: Every sensor is calibrated in a precision humidity calibration chamber, storing specific calibration coefficients inside its OTP memory for automatic internal signal processing.
• High Anti-Interference & Stability: Utilizes dedicated digital module acquisition technology to ensure exceptional long-term stability and strong resistance to noise.
• Single-Bus Digital Communication: Transmits 40 bits of high-bit-first data over a single signal line, simplifying microcontroller wiring and freeing up GPIO pins.
• Low Power & Long Distance: Highly energy-efficient design capable of transmitting accurate data over extended cable runs.

Common Applications

• HVAC & Dehumidifiers: Automated heating, ventilation, air conditioning, and humidity control systems.
• Weather Stations & Data Loggers: Precision climate tracking in indoor or outdoor environmental monitoring stations.
• Home Appliances & Consumer Goods: Integrating ambient environmental monitoring into smart home appliances.
• Automotive & Medical Equipment: Monitoring critical atmospheric conditions in testing, inspection, and healthcare environments.

Usage Tips

• 2-Second Sampling Interval: The sensor requires a 2-second sampling period between reads. Requesting data faster than every 2 seconds will return stale values or cause internal self-heating.
• Data Line Pull-Up Resistor: When using the raw 4-pin AM2302 component, place a 4.7kΩ to 10kΩ pull-up resistor between the DATA line and VCC rail to maintain clean digital communication.
• Data Transmission Format: Reads return 40 bits total—16 bits for humidity data, 16 bits for temperature data, and an 8-bit parity checksum to verify transmission integrity in code.

Supply Voltage Note: While official datasheets specify a 3.0V–5.5V operating range, certain clone/third-party breakout modules have been reported to fail or read erratically on a 5V power supply, operating reliably only on 3.3V. If you experience checksum errors or timeout issues on 5V, power the module from a stable 3.3V rail instead.