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The SHT31 temperature sensors

Typical current

150µA (active)

Price

Medium

Maximum precision

±0,3 °K

Measurement range (°C)

−40 / +125

Resolution

16 bits

Power supply voltage

2,4→5,5V

Sampling rate

1 to 10Hz

I²C Address

0x44

The SHT31 is an integrated digital temperature and humidity sensor developed by Sensirion (Switzerland).

It succeeds the SHT21 and SHT15, offering improved accuracy, long-term stability, and immunity to contaminants (thanks to its optional protective coating).

It is a preferred component for all ambient measurement applications where reliability and calibration are essential.

The SHT31 uses two internal sensing elements:

  • an integrated temperature measurement diode (for compensation calculation),
  • a capacitive humidity sensor whose dielectric constant varies with moisture content.

These two measurements are converted into digital values via a 16-bit ADC and transmitted via I²C.

The conversion equations are standardized by Sensirion:

SHT31 Sensors

where S_T and S_RH are the raw values read (16 bits).

Raw measurement (hex)
 Temperature (°C) Humidity (%)
0x0000 −45,0 0,0
0x8000 +42,5 50,0
0xFFFF +130,0 100,0

💡 The output is linear and factory calibrated — no additional correction needed.

+3.3V
 │
[SHT31]
 │ SDA ─────────┐
 │ SCL ─────────┤── [I²C Microcontroller]
 │ ADDR (option)
 │ GND

💡 ADDR connected to GND → 0x44; to VCC → 0x45.

Two SHT31 sensors can coexist on the same bus.

🌤️ Connected weather stations

🧠 IoT and home automation systems

⚙️ Climate chambers and HVAC

🧪 Environmental instrumentation

🏭 Industrial humidity/temperature monitoring

Smooth tube probe

Should I choose an SHT31 sensor?

Here are 3 strengths and 3 weaknesses to help you make your choice.

Strengths points

  • 🎯 High precision double measurement
         → ±0.3 K in temperature and ±2% RH, factory calibrated.
  • 💨 Fast response time
         → Complete measurements in less than 10 ms — ideal for dynamic applications.
  • 🧱 Compact and protected case
         → Available with PTFE coating or hydrophobic protection filter.
  • ⚡ Stable digital calibration
         → Each sensor is individually calibrated with internal EEPROM coefficients.
Waterproof probe

Weak points

  • 🌬️ Sensitivity to deposits and contaminants
    → Without protection, the sensor can drift in dusty or oily environments.
  • 📡 Interface only I²C
    → No SPI version, some industrial applications prefer the differential bus.
  • 💸 Cost higher than a simple temperature sensor
    → But justified by the dual measurement and the reliability of Sensirion.

Useful information

Here is some useful information regarding the SHT31 sensors.

Command (hex)
 Mode Description
0x2400 High repeatability, no clock stretching Complete measurement (T + RH)
0x240B Medium repeatability Less precise, faster
0x2416 Low repeatability For energy savings
0xE000 Read status register State reading
0x30A2 Soft reset Software reset 
i2c_start();
i2c_write(0x44 << 1);
i2c_write(0x24);
i2c_write(0x00);
delay(15); // Waiting for conversion
i2c_start();
i2c_write((0x44 << 1) | 1);
MSB_T = i2c_read_ack();
LSB_T = i2c_read_ack();
CRC_T = i2c_read_ack();
MSB_RH = i2c_read_ack();
LSB_RH = i2c_read_ack();
CRC_RH = i2c_read_nack();
i2c_stop();

S_T = (MSB_T << 8) | LSB_T;
S_RH = (MSB_RH << 8) | LSB_RH;
temp = -45 + (175.0 * S_T / 65535.0);
rh = 100.0 * S_RH / 65535.0;

✅ Example:

S_T = 29,000 → T = 31.6 °C

S_RH = 36,000 → RH = 54.9 %

3.3V ───────────┐
                │
               [SHT31]
                │ SDA ───────┐
                │ SCL ───────┤── MCU (Arduino, ESP32, STM32…)
                │ GND

💡 Provide pull-up resistors of 10 kΩ if not included on the module.

Bit Nom Description
15 Alert pending An alert is active
11 Heater Internal heating activated
4–0 CRC status CRC verification of data
💡 The internal heating can be activated to dry the sensor in extreme humidity conditions.
Temperature (°C) Error (K) HR Error (%)
−40 ±0,5 ±3,0
0 ±0,3 ±2,0
50 ±0,3 ±2,0
100 ±0,4 ±3,0

💡 The SHT31 remains accurate even after hundreds of humidity cycles — its typical annual drift is <0.25% RH.

The SHT31 offers excellent accuracy for the combined measurement of temperature and humidity, in a compact format.


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