ESP8266 Community Forum

- Sun Nov 22, 2015 12:32 pm #34692 I'm running one of each right here on my desk, both are on ESP01's, using the same exact sketch just calling out the sensor differently, the DHT22 is showing about 10% higher RH than the DHT11. No filter caps on power input but I am running them on the dual voltage BB power supplies set on 3.3v so there is a cap on there I presume is a filter cap. Both have a 10k pull up resister on the GPIO that the DHT is on.

This is the Sketch I am using................

http://www.arduinesp.com/thingspeak

Bill

- Mon Nov 23, 2015 10:19 am #34774

I have the same results, DHT22 gives higher values than DHT11. Red is the DHT11, black the DHT22.

- Mon Nov 23, 2015 6:26 pm #34819 This variation between sensors in the same position is troubling. When I have more time I will calibrate with a table salt solution that gives a fixed humidity of a reasonable range of temperatures...I'm hoping DHT22 or the DHT11 has an accurate value. If they don't it could be a commercial code library issue. I have DHT11 code for a PIC processor that agrees with humidity I get with the commercial code library for the DHT11. I suspect there is an issue with the commercial DHT22 code and the esp8266 Arduino IDE.
The DHT22 is consistent between DHT22's but is I believe way to high for RH.

- Tue Nov 24, 2015 5:37 am #34855 Here there is a descriptio of a sort of calibration made with salts.
http://www.kandrsmith.org/RJS/Misc/calib_dht22.html
Other post describes a comparison between DHT11, DHT22 and Sensirion SHT71
http://www.kandrsmith.org/RJS/Misc/calib_dht22_dht11_sht71.html