I2C SHT21 Digital Temperature and Humidity SensorProduct Name: SHT21 Digital Temperature and Humidity SensorSensor Type: Combined digital humidity and temperature sensorInterface: I²C (Inter-Integrated Circuit)Manufacturer: Sensirion AG (original design)Package Type: Surface Mount (DFN – Dual Flat No-leads), breakout board availableElectrical CharacteristicsSupply Voltage Range: 2.1V to 3.6V DCTypical Operating Voltage: 3.0V DCMaximum Supply Current: <1.5 mA (measuring)Sleep Mode Current: <0.15 µACommunication Interface: I²C (2-wire: SDA & SCL)I²C Address: 0x40 (7-bit address)Logic Voltage Levels: Compatible with 3.3V and 5V microcontrollers (via level shifting)Max Clock Frequency: 400 kHz (Fast Mode I²C)Measurement SpecificationsHumidity MeasurementMeasurement Range: 0% RH to 100% RHTypical Accuracy: ±2% RH (20% – 80% RH), ±3% RH (full range)Repeatability: ±0.1% RHResolution:12-bit (default), 8-bit (configurable)Response Time: ~8 seconds (tau63%)Hysteresis: ±1% RHTemperature MeasurementMeasurement Range: –40°C to 125°CTypical Accuracy: ±0.3°C (0°C to 60°C), up to ±0.9°C over full rangeRepeatability: ±0.1°CResolution:14-bit (default), 12-bit (configurable)Response Time: ~5 seconds (tau63%)Sensor FeaturesDigital Output: Calibrated and linearized digital I²C outputFactory Calibrated: YesChecksum Support: CRC-8 for data integrity verificationStatus Bits: End-of-conversion, heater status, etc.Integrated Heater: For self-test and dehumidification (controllable)Low Power Consumption: Suitable for battery-powered applicationsPhysical & Mechanical PropertiesSensor Dimensions (chip): ~3 × 3 × 1.1 mm (DFN package)Breakout Board Size (if applicable): ~15mm × 10mmPinout (4-pin):VCC – Power Supply (2.1V – 3.6V)GND – GroundSCL – Serial Clock LineSDA – Serial Data LineEnvironmental & ProtectionOperating Temperature Range: –40°C to 125°COperating Humidity Range: 0% RH to 100% RH (non-condensing)Long-Term Stability:Humidity Drift: <0.5% RH/yearTemperature Drift: <0.04°C/yearRobustness: Fully calibrated, no need for external componentsOptional Protective Filter Cap: Available for harsh environmentsSoftware & CommunicationData Protocol: I²C with master-slave architectureTypical Commands:Trigger Temperature Measurement (Hold/No Hold Master Mode)Trigger Humidity Measurement (Hold/No Hold Master Mode)Read the user registerWrite the user register8-bit CRC Checksum on each transmissionDriver Support:Libraries available for Arduino, Raspberry Pi, ESP32, STM32Compatible with Linux, Windows, RTOS, and embedded systems SKU: LKSEN00045 Category: Sensors
