Poor Accuracy of DHT11 Temperature and Humidity Sensor, Not Recommend

This article is combined on many test results from different users. It just expresses the original author's comments. Because there are so many common users who are still selecting DHT11 temperature and humidity sensor as their choice. So it is necessary to let them know the poor accuracy of DHT11 sensor.

DHT11 temperature humidity sensor mainly includes resistance type humidity sensing IC and NTC temperature part. Its main feature is low cost. But its temperature accuracy is +/- 2℃ that means the Max error can be 4℃, so this error is big for daily using, not mention high accuracy commercial and industrial application. About humidity,DHT11 marks +/-5%RH,however, in fact, the accuracy is really very very poor, and it is just only a reading value, not any reference sense.

The following is one of the test result from REALDAI:
I use DHT11 to gather temperature and humidity, i'm electronic major student in a college. The temperature is 2℃ error. But its humidity measurement is very poor. Because it is rain here, but the humidity is still 33%. This is a big error.

A replies from another man:
I also found the accuracy of DHT11 is not good. In order to know why, i open its enclosure and found it is a small integrated circuit, and use a NTC to test temperature. So you can see its accuracy can't be good.

Another person comments:
The temperature accuracy of DHT11 is just so and about +/- 2℃,but its humidity error is very big (at least over 30%), and all of the reading value is lower.

Thus, the company of DHT11 has to release its new version DHT22(also called as AM2302). The company announces that it is better than DHT11 and it can be used to replace SHT1X series temperature and humidity sensor. Of course, AM2302/DHT22 is much more expensive than DHT-11. The following is TWO test result:

1.DHT11 VS DHT22(AM2302) Temp. and humidity Sensor
This test is from ID BXZYF:
In the past,I always use DHT11 to test humidity and didn't notice its accuracy. Today in order to improve result, i bought 4 pieces of DHT22(AM2302). As a result, the result is big difference:
DHT11: 39%
DHT22:61.2%
The weather standard: light rain, temperature:16℃, related humidity: 69%.

2.SHT1X VS DHT22(AM2302) Temp. and humidity Sensor
Main Components:
DFROBOT    DHT22 2NOS
DFROBOT    SHT1X 2NOS
DFROBOT    NANO3.0 1NO
DFROBOT NANO Expand 1NO
High accuracy mechanical temp. humidity meter 1NO

Arduino Code:

#include
#include

SHT1x SHT(7, 8);
DHT22 DHT1(2);
DHT22 DHT2(4);

void setup()
{
Serial.begin(9600);
}

void loop()
{
Serial.print("SHT: ");
Serial.print(SHT.readTemperatureC(),2);
Serial.print("C ");
Serial.print(SHT.readHumidity(),2);
Serial.print("%");

DHT22_ERROR_t errorCode;
Serial.print(" DHT1: ");
errorCode = DHT1.readData();
if(errorCode==DHT_ERROR_NONE){
Serial.print(DHT1.getTemperatureC(),2);
Serial.print("C ");
Serial.print(DHT1.getHumidity(),2);
Serial.print("%");
}
else {
Serial.print("Error");
}
Serial.print(" DHT2: ");
errorCode = DHT2.readData();
if(errorCode==DHT_ERROR_NONE){
Serial.print(DHT2.getTemperatureC(),2);
Serial.print("C ");
Serial.print(DHT2.getHumidity(),2);
Serial.print("%");
}
else {
Serial.print("Error");
}
Serial.println("");
delay(3000);
}

The result after software running is listed as below:

Conclusion:

1.DHT22 is better than DHT11. So it is no need to consider DHT11 temperature and humidity sensor unless there is special requirement.

2.Comparing with SHT10X digital temperature and humidity sensor, DHT22 should be ok on temperature measurement, but for humidity measurement, its accuracy is still poorer than SHT10x. In regard that DHT22 is not cheap again, SHT10X should be your better solution if possible.

3.No matter DHT or SHT sensor, they still require users to master related programming language(e.g.C),thus it will be difficult for common users to use it.

In order to solve the problem of them, we have released complete version digital temperature and humidity sensors with high cost-effective solution,whose performance is better than DHT11 or DTH22. The complete version can support digital RS485(Modbus) output or analog output(4-20mA,0-5V,0-10V). Our products have been widely used for various of industries and exported to many countries and areas.

For your reference,the following are part of our temperature and humidity sensors: