The **SHT40-AD1B-R2** is a high-precision digital humidity and temperature sensor manufactured by Sensirion. It is part of the 4th generation (SHT4x) series, designed for high-volume applications with low power consumption and high reliability. --- ### 1. Key Technical Specifications | Parameter | Specifications | | :--- | :--- | | **Interface** | I2C (Standard, Fast Mode Plus, High Speed) | | **Supply Voltage (VDD)** | 1.08 V to 3.6 V | | **Avg. Current (at 1 Hz)** | 0.4 µA (Idle: 80 nA) | | **RH Accuracy** | ±1.8% RH | | **Temp. Accuracy** | ±0.2 °C | | **Package** | 4-pin DFN (1.5 x 1.5 x 0.5 mm) | | **Operating Range** | 0 to 100% RH; -40 to 125 °C | --- ### 2. Core Electronic Features #### A. Internal Integrated Heater The SHT40 features an on-chip programmable power heater. This serves two main purposes: 1. **De-icing:** Prevents condensation and removes water droplets from the sensor membrane. 2. **Self-test:** Used to verify sensor integrity in harsh environments. #### B. Digital Interface (I2C) The sensor communicates via a standard I2C bus. The "AD1B" variant typically indicates a specific I2C address (usually `0x44`) and specific output characteristics. * **SCL (Serial Clock):** Handles synchronization. * **SDA (Serial Data):** Bidirectional line for data transfer. #### C. Energy Harvesting Compatibility Due to its extremely low power consumption (nano-ampere range in idle), this part is ideal for battery-operated IoT devices and energy-harvesting systems where power budgets are tight. --- ### 3. Pin Configuration (4-pin DFN) | Pin No. | Name | Description | | :--- | :--- | :--- | | 1 | **SDA** | Serial Data (Bidirectional) | | 2 | **SCL** | Serial Clock (Input) | | 3 | **VDD** | Supply Voltage | | 4 | **VSS** | Ground | --- ### 4. Application Example (C++ Pseudo-code) ```cpp // Example of reading SHT40 data via I2C #include #define SHT40_ADDR 0x44 void readSensor() { Wire.beginTransmission(SHT40_ADDR); Wire.write(0xFD); // Command: High precision measurement Wire.endTransmission(); delay(10); // Wait for measurement Wire.requestFrom(SHT40_ADDR, 6); // Request 6 bytes (Temp + CRC, RH + CRC) // ... Process bytes to convert to Temperature and Humidity } ```