How to Use SHT31: Examples, Pinouts, and Specs

The SHT31, manufactured by Sensirion, is a digital humidity and temperature sensor designed to deliver highly accurate measurements of relative humidity and temperature. It features a high level of precision, low power consumption, and a fast response time. The SHT31 is equipped with a digital I²C interface, making it easy to integrate into a wide range of applications.

• Weather stations
• HVAC (Heating, Ventilation, and Air Conditioning) systems
• Environmental monitoring
• Industrial process control
• Smart home devices
• Data loggers

The SHT31 sensor is designed to provide reliable and precise measurements under various environmental conditions. Below are its key technical details:

The SHT31 is typically available in a 4-pin package. Below is the pinout description:

The SHT31 is straightforward to use in a circuit, thanks to its I²C interface. Below are the steps and considerations for integrating the sensor:

1. Connect the VDD pin to a 3.3V or 5V power supply.
2. Connect the GND pin to the ground of your circuit.
3. Connect the SDA pin to the I²C data line of your microcontroller (e.g., Arduino UNO).
4. Connect the SCL pin to the I²C clock line of your microcontroller.
5. Use pull-up resistors (typically 4.7 kΩ) on the SDA and SCL lines if not already present.

Below is an example Arduino sketch to read temperature and humidity data from the SHT31 sensor using the Adafruit SHT31 library:

#include <Wire.h>
#include "Adafruit_SHT31.h"

// Create an instance of the SHT31 sensor
Adafruit_SHT31 sht31 = Adafruit_SHT31();

void setup() {
  Serial.begin(9600); // Initialize serial communication
  while (!Serial) delay(10); // Wait for serial monitor to open

  // Initialize the SHT31 sensor
  if (!sht31.begin(0x44)) { // 0x44 is the default I²C address
    Serial.println("Failed to find SHT31 sensor!");
    while (1) delay(1); // Halt execution if sensor is not found
  }
  Serial.println("SHT31 sensor initialized.");
}

void loop() {
  // Read temperature and humidity
  float temperature = sht31.readTemperature();
  float humidity = sht31.readHumidity();

  // Check if readings are valid
  if (!isnan(temperature) && !isnan(humidity)) {
    Serial.print("Temperature: ");
    Serial.print(temperature);
    Serial.println(" °C");

    Serial.print("Humidity: ");
    Serial.print(humidity);
    Serial.println(" %");
  } else {
    Serial.println("Failed to read data from SHT31 sensor.");
  }

  delay(2000); // Wait 2 seconds before the next reading
}

• Use decoupling capacitors (e.g., 0.1 µF) near the VDD pin to stabilize the power supply.
• Avoid exposing the sensor to extreme conditions (e.g., condensation, dust) to maintain accuracy.
• Calibrate the sensor if required for high-precision applications.
• Ensure proper pull-up resistors are used on the I²C lines to avoid communication issues.

1. Sensor Not Detected on I²C Bus

   • Ensure the correct I²C address (default: 0x44) is used in your code.
   • Verify the SDA and SCL connections and check for proper pull-up resistors.
   • Confirm that the power supply voltage is within the specified range (2.4V to 5.5V).

2. Incorrect or Unstable Readings

   • Check for noise or instability in the power supply. Use decoupling capacitors if needed.
   • Ensure the sensor is not exposed to condensation or contaminants.
   • Verify that the sensor is not placed near heat sources or strong airflow.

3. Arduino Code Compilation Errors

   • Ensure the Adafruit SHT31 library is installed in the Arduino IDE.
   • Verify that the correct board and port are selected in the Arduino IDE.

Q: Can the SHT31 operate at 5V?
A: Yes, the SHT31 can operate with a supply voltage between 2.4V and 5.5V, making it compatible with both 3.3V and 5V systems.

Q: What is the default I²C address of the SHT31?
A: The default I²C address is 0x44. Some variants of the sensor may support an alternate address of 0x45.

Q: How can I protect the sensor in harsh environments?
A: Use a protective cover or filter to shield the sensor from dust, water, and other contaminants while allowing air to pass through.

Q: Can the SHT31 measure dew point?
A: The SHT31 does not directly measure dew point, but you can calculate it using the temperature and humidity readings.

By following this documentation, you can effectively integrate and use the SHT31 sensor in your projects.