DHT temperature and humidity sensors, are very basic and slow, but are great for hobbyists who want to do some basic data logging. Each DHT is made of two parts: Capacitive Humidity Sensor and Thermistor. There is also a very basic chip inside that does some analog to digital conversion and spits out a digital signal containing temperature and humidity readings. This digital signal can be read by any microcontroller.
Below is a table comparing the specs of DHT11 and DHT22. When a sensor lead in a row, it will win one point, at the end we’ll see the scores for each one.
|
DHT11 |
DHT22 |
Winner |
|
|
Price |
Ultra low cost |
Low Cost |
DHT11 – Points: 1 |
|
Voltage |
3 to 5V power and I/O |
3 to 5V power and I/O |
– |
|
Maximum Current Use |
2.5mA max current use during conversion (while requesting data) |
2.5mA max current use during conversion (while requesting data) |
– |
|
Humidity Reading Range |
20 to 80% with 5% accuracy |
0 to 100% with 2 to 5% accuracy |
DHT22 – Points: 2 |
|
Temperature Reading Range |
0 to 50°C with ± 2°C accuracy |
-40 to 80°C with ± 0.5°C accuracy |
DHT22 – Points: 4 |
|
Sampling Rate |
1Hz (Once every second) |
0.5Hz (Once every two seconds) |
DHT11 – Points: 2 |
|
Body Size |
15.5x12x5.5 mm |
15.1x25x7.7 mm |
DHT11 – Points: 3 |
|
Pinout |
4 pins with 0.1” spacing |
4 pins with 0.1” spacing |
– |
So DHT22 wins having 1 point over DHT11, but what matters is the range that you want to read, the frequency of reading can also be important for some application.
DHT22 is better then DHT11, but it isn’t a waterproof sensor, check DS18B20 for waterproof temperature sensor.
