Humidity measurement is essential in many electronics projects, including weather stations, indoor climate monitoring, greenhouse control and industrial applications. While many temperature sensors also provide humidity readings, not all sensors deliver the same level of accuracy and stability.
This article compares the most common humidity sensor families used in Arduino and ESP32 projects, including DHT, AHT, SHT and HDC1080.
How Humidity Sensors Work
Most modern humidity sensors are based on capacitive measurement. They detect changes in capacitance caused by moisture in the air.
- Higher humidity changes the dielectric properties of the sensor material
- This change is converted into a digital value
- Temperature compensation is usually built into the sensor
Because humidity measurement is sensitive to environmental conditions, calibration and sensor quality are very important.
DHT Sensors: The Legacy Option
- Examples: DHT11, DHT22
- Interface: proprietary single-wire protocol
- Humidity accuracy: typically ±2-5%
DHT sensors are widely used due to their low cost and simple wiring, but they are increasingly outdated.
Advantages:
- Very cheap
- Easy to find
Limitations:
- Slow update rate
- Timing-sensitive communication
- Variable quality between manufacturers
- Poor long-term stability
DHT sensors are acceptable for simple hobby projects but should be avoided in new designs when better options are available.
AHT Series: Modern Budget-Friendly Sensors
The AHT series provides a modern alternative to DHT sensors with better stability and easier integration.
Advantages:
- Stable and consistent readings
- No timing-critical communication
- Fast response time
- Good price-performance ratio
These sensors are ideal for most general-purpose applications.
SHT Series: High-Precision Sensors
- Examples: SHT30, SHT40
- Interface: I2C
- Humidity accuracy: up to ±1.5%
SHT sensors from Sensirion are known for high accuracy and excellent long-term stability.
Advantages:
- Very high precision
- Excellent repeatability
- Reliable calibration
Typical use cases:
- Weather stations
- Indoor climate monitoring
- Industrial and laboratory environments
HDC1080: A Strong Alternative
- Interface: I2C
- Humidity accuracy: typically ±2%
- Low power consumption
The HDC1080 from Texas Instruments is another reliable humidity sensor, offering good accuracy and very low power consumption.
It is particularly useful in battery-powered applications where energy efficiency is critical.
Comparison Overview
| Sensor | Interface | Accuracy | Speed | Stability | Recommendation |
|---|---|---|---|---|---|
| DHT11 | Custom | Low | Very slow | Poor | Avoid |
| DHT22 | Custom | Moderate | Slow | Moderate | Legacy use |
| AHT20/21/25 | I2C | Good | Fast | Good | Best value |
| SHT30/40 | I2C | Very high | Fast | Excellent | Precision applications |
| HDC1080 | I2C | Good | Fast | Good | Low-power projects |
Environmental Factors
Humidity sensors are sensitive to environmental conditions:
- Condensation can damage sensors
- Dust and chemicals affect accuracy
- Long-term exposure can cause drift
Proper placement and occasional recalibration improve reliability.
Power and Integration
- Most sensors operate at 3.3V
- I2C sensors require pull-up resistors
- Keep wiring short for best accuracy
Practical Recommendations
- Use AHT20 or AHT21 for general-purpose projects
- Use SHT30 or SHT40 when accuracy matters
- Use HDC1080 for low-power designs
- Avoid DHT sensors in new designs
Conclusion
Humidity measurement requires stable and well-calibrated sensors. While DHT sensors are still common, modern I2C-based sensors such as AHT and SHT provide significantly better performance and reliability.
For most applications, AHT sensors offer the best balance between cost and performance, while SHT sensors are the preferred choice for precision systems.