The SHT temperature and humidity sensors from Sensirion are among the most precise, reliable options out there for measuring environmental conditions. Whether you’re building a weather station, monitoring your greenhouse, or adding climate control to a smart home device, the SHT line offers features you need — with minimal fuss. In this guide, you’ll get everything: sensor variants, specs, wiring, code, and practical tips.
What are SHT Sensors?
SHT sensors are digital temperature & humidity sensors made by Sensirion. They use CMOSens® technology to combine temperature and relative humidity measurements in one package, with fast response times, low drift, and high reliability. They communicate over I²C (in almost all variants), making them very compatible with microcontrollers like ESP32, Arduino, Raspberry Pi, etc.
Why choose SHT?
- They offer good accuracy (some models ±0.1 °C / ±1 % RH) which is better than many cheap sensors.
- They are calibrated in factory, reducing calibration work.
- Lower power consumption variants are available so they suit battery powered setups.
- Wide operating range (temperature, humidity), good for indoor/outdoor or harsh environments.
SHT Series Overview & Comparisons
Here are the main series in the SHT family, with their strengths, trade-offs, and parameters you should check.
| Series | Example Models | Temperature Range | Humidity Range | Accuracy (Temp / Hum) | Typical Supply Voltage | Best Use Case |
|---|---|---|---|---|---|---|
| SHT2x | SHT20, SHT21, SHT25 | approx −40 °C .. +125 °C | 0 % .. 100 % RH | Temp ~±0.3 °C, Hum ~±3 % RH | ~2.1-3.6 V | Basic uses, when high precision is not critical, proven track record |
| SHT3x | SHT30, SHT31, SHT35 | similarly wide, sometimes narrower in humidity extremes | High RH, up to 100 % (non-condensing) | Temp ~±0.1-0.3 °C, Hum ~±1.5-3 % RH depending on model | ~2.15-5.5 V | Indoor/outdoor monitoring, projects where speed & precision matter more |
| SHT4x | e.g. SHT40, SHT45 | −40 °C .. +125 °C | 0-100 % RH (non-condensing) | Best precision in the range, Temp ±0.1 °C, Hum even ±1 % RH on good models | Some variants support very low voltage operation | Battery powered or ultra low-power applications, where every mA counts |
Sensor Details & Wiring
Pin / Package Types
Most SHT sensors come in small surface-mount packages (SMD) or modules/breakouts. The pinout is simple:
- VCC (power)
- GND (ground)
- SCL (I²C clock)
- SDA (I²C data)
- Sometimes a data ready or alert pin on higher end models
Wiring Basics (I²C)
| Connection | From SHT Sensor | To Microcontroller |
|---|---|---|
| VCC | VCC pin | 3.3 V (or supply in supported range) |
| GND | GND pin | Ground |
| SDA | Data line | SDA pin on MCU (with pull-ups) |
| SCL | Clock line | SCL pin on MCU (with pull-ups) |
Tips:
- Use pull-up resistors on SDA and SCL if your board doesn’t already have them (4.7-10 kΩ commonly used).
- Keep the I²C lines as short as possible for better signal integrity.
- Avoid routing the sensor where it sees heat from other components.
- If used outdoors, protect from direct water contact, but ensure air can move.
Key Specs & What They Mean
When choosing or using an SHT sensor, pay attention to:
- Response time: how quickly temperature/humidity adjusts to changes. Important in dynamic environments.
- Accuracy / precision: how close the reading is to “true”, and how stable it is over time or under changing conditions.
- Long term drift: how much the readings shift over time. Sensirion claims low drift for SHT sensors.
- Supply voltage range: some models can run on lower voltages (good for battery).
- Power consumption / sleep mode: for battery powered projects, know how much power is used in idle or sleep, and how much when measuring.
- Operating environment: ranges of humidity and temperature, condensation risk. Some sensors degrade if exposed to condensate or extreme moisture.
- Mechanical protection: filters, membranes, waterproofing or protective enclosures if needed.
Example: Using SHT31 with ESP32
Here’s a practical project snippet to get you going.
Wiring
- SHT31 VCC → 3.3 V on ESP32
- SHT31 GND → GND
- SHT31 SDA → GPIO21 (or another I²C SDA pin)
- SHT31 SCL → GPIO22 (or another I²C SCL pin)
Code Example (Arduino / ESP32)
#include <Wire.h>
#include "Adafruit_SHT31.h"
Adafruit_SHT31 sht31 = Adafruit_SHT31();
void setup() {
Serial.begin(115200);
Wire.begin(21, 22); // SDA, SCL pins
if (!sht31.begin(0x44)) { // typical I2C address for SHT31
Serial.println("Couldn't find SHT31 sensor!");
while (1) delay(10);
}
}
void loop() {
float temperature = sht31.readTemperature();
float humidity = sht31.readHumidity();
if (! isnan(temperature)) {
Serial.print("Temperature: ");
Serial.print(temperature);
Serial.print(" °C ");
} else {
Serial.print("Temp read error ");
}
if (! isnan(humidity)) {
Serial.print("Humidity: ");
Serial.print(humidity);
Serial.println(" %RH");
} else {
Serial.println("Hum read error");
}
delay(2000); // adjust to your application
}
Things to Watch
- Warm-up time: sensors may need a short time after power up to stabilize.
- Calibration / offset correction: although calibration is done by the factory, small offsets can still exist. You can compare with a reference sensor and adjust.
- Avoid placing the sensor near heat sources, or in direct sunlight.
- Condensation: if RH is near 100 %, ensure that moisture does not collect on the sensor itself.
Common Mistakes & Best Practices
Based on lots of projects, these are things that often go wrong / tips to make things better:
- Ignoring wiring pull-ups: I²C lines without pull-ups can give noisy or no readings.
- Using the wrong supply voltage: some SHT models aren’t rated for 5 V.
- Mechanical stress or bending: if using SMD sensors in a PCB that flexes, you could damage them.
- Expecting perfect specs always: datasheet values are under ideal conditions; your environment (dust, moisture, temperature swings) will introduce errors.
- Infrequent readings but leaving power on: better to power them down or sleep if not measuring often (depending on your SHT model’s power usage).
Which Model Should You Pick?
Here are some guidelines:
- If you want good value and decent accuracy: SHT30 or SHT31 are solid choices.
- If you need higher precision, and want to measure small changes, go for SHT35 or SHT45.
- If battery life is important, or you want ultra-low power, pick a model from SHT4x.
- For outdoor use: pick a version with protective casing or plan for mechanical protection.
Conclusion
SHT sensors bring together precision, reliability, and ease of use in a compact package. If you follow good wiring practices, protect the sensor from harsh conditions, and choose the right variant for your accuracy/power trade-offs, they’ll serve well in lots of projects — from indoor climate control to outdoor monitoring.