SHT75 | GUILCOR SENSORS

SHT75
Temperature sensors

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Temperature range
-40 / 124°C

Temperature precision
+/- 0,3°K

Humidity precision
+/-1,8% RH

Resolution (T° et Hr)
14 and 12 bits

Power supply voltage

2,4→5,5V

Response time

210 and 55 ms

Typical current
550 mA

Price
High

What is a SHT75 sensor ?

The SHT75 is a high-precision digital temperature and humidity sensor developed by Sensirion, a major player in the industry.

Unlike the DHT11/DHT22, it is individually calibrated at the factory and stores its calibration coefficients in an integrated EEPROM, ensuring metrological traceability.

It is widely used in:

industrial and HVAC monitoring,
professional weather stations,
and laboratory measurement systems.

Operating principle

The SHT75 integrates:

a polymer capacitive cell sensitive to humidity,
an integrated diode temperature sensor,
a 14-bit ADC and a digital processor.

The measurements are transmitted in digital form via a 2-wire synchronous interface, similar to SPI (Signal + Clock + Power + Ground).

Official conversion formulas (Sensirion):

T (°C)   = -39.7 + 0.01 × SO_T

RH (%)   = -2.0468 + 0.0367 × SO_RH - 1.5955 × 10^{-6} × SO_RH²

💡 SO_T and SO_RH = raw values from the sensor (0–16383 for 14 bits).

Example of digital conversion (pseudo-code SPI-like)

uint16_t readSensor(uint8_t command) {
  sendCommand(command);
  waitForMeasurement();
  return read16Bits();
}

float temperature = -39.7 + 0.01 * readSensor(0x03);
float humidity = -2.0468 + 0.0367 * readSensor(0x05)
                 - 1.5955e-6 * pow(readSensor(0x05), 2);

✅ Typical example:

SO_T = 25300 → T = 213.3 °C

SO_RH = 21000 → HR = 48.2 %

Principle diagram

+3.3V
 │
[SHT75]
 │ DATA ───────┐
 │ SCK ────────┤── MCU (STM32, Arduino, ESP32…)
 │ GND

💡 The interface is "bit-bang" compatible with SPI or I²C depending on the microcontroller.

Application areas

🧠 Precision instrumentation

🏭 Industrial control and laboratories

🌿 Greenhouses and clean rooms

🌡️ Professional weather stations

💧 Climate monitoring of buildings

Should I choose a SHT75 sensor ?

Strengths points

🎯 High precision calibrated
→ ±0.3 K and ±1.8 % RH, individually calibrated, traceable.
⚙️ Simple yet robust interface
→ 2-wire protocol compatible with SPI/I²C, easy to implement.
🧠 Integrated compensation
→ Temperature and humidity correlated to correct the measurements.
💪 Long-term stability
→ Drift <0.5% RH/year, perfect for sustainable use.

Weaknesses points

💰 Higher price
→ More expensive than the DHT and SHT3x, but justified by its accuracy.
📡 Non-standardized protocol
→ No native I²C compatibility, requires specific code.
💨 Moderate measurement time (~200 ms)
→ Not suitable for ultra-fast acquisitions.