Temperature Sensors: DS18B20, DHT11, DHT22, AHT20, AHT21, AHT25, SHT30 and SHT40

Temperature measurement is one of the most common tasks in electronics projects. From simple room monitoring to industrial control systems, choosing the right temperature sensor has a direct impact on accuracy, reliability and ease of use.

This article compares the most widely used temperature sensors in Arduino-compatible projects, including DS18B20, DHT series, AHT series and SHT series sensors.

Common Types of Temperature Sensors

Temperature sensors used in electronics typically fall into three categories:

• Analog sensors (NTC thermistors, LM35)
• Digital single-wire sensors (DS18B20, DHT series)
• Digital I2C sensors (AHT20, SHT30, SHT40)

Modern designs strongly favor digital I2C sensors due to better accuracy and easier integration.

DS18B20: The One-Wire Classic

• Interface: One-Wire
• Temperature range: -55°C to +125°C
• Accuracy: typically ±0.5°C
• Resolution: 9 to 12 bit

The DS18B20 is one of the most popular temperature sensors. It uses the One-Wire protocol, allowing multiple sensors to share a single data line.

Advantages:

• Very robust and reliable
• Long cable lengths possible
• Unique ID for each sensor

Limitations:

• Slower response time
• Requires timing-sensitive communication
• No humidity measurement

DHT11 and DHT22: Low-Cost Temperature + Humidity

The DHT series sensors are still widely used, but they are increasingly being replaced by modern I2C sensors.

Limitations:

• Slow update rate
• Timing-sensitive protocol
• Inconsistent quality between manufacturers

AHT Series: Modern Low-Cost I2C Sensors

• Interface: I2C
• Examples: AHT20, AHT21, AHT25
• Temperature accuracy: typically ±0.3°C
• Humidity accuracy: typically ±2%

The AHT series is a modern replacement for DHT sensors. They are inexpensive, stable and easy to use with I2C.

Advantages:

• Fast response time
• Stable calibration
• No timing-critical communication

For most projects, AHT20 or AHT21 are excellent default choices.

SHT Series: Higher-End Precision Sensors

• Interface: I2C
• Examples: SHT30, SHT40
• Temperature accuracy: up to ±0.2°C
• Humidity accuracy: up to ±1.5%

Sensirion SHT sensors are known for high precision and reliability.

Advantages:

• Very high accuracy
• Excellent long-term stability
• Good performance in demanding environments

Typical use cases:

• Environmental monitoring
• Weather stations
• Industrial control systems

Comparison Overview

Power and Voltage Considerations

• Most sensors operate at 3.3V
• Many breakout boards support 5V input but use 3.3V logic
• I2C sensors require pull-up resistors
• Long cables may require careful signal design

Practical Recommendations

• Use AHT20 or AHT21 for most projects
• Use SHT30 or SHT40 for higher accuracy
• Use DS18B20 for long cable runs or multiple sensors
• Avoid DHT11 for new designs

Conclusion

While older sensors like DHT11 and DHT22 are still widely available, modern I2C sensors such as AHT and SHT series provide better accuracy, faster response and easier integration.

For most Arduino and ESP32 projects, switching to I2C-based sensors is the best long-term choice.