ESP32 WROOM + BME280 in a box

[meneldor]

Hello,

Here is my (almost) complete EPS32 project part of my home iot mesh with Openhab2:

esp_project.jpg (3.21 MiB) Viewed 4247 times

The box is 72x72cm. The sensor is BME280 and left of it is the header for a CCS811 where i currently plugged another external BME280 to compare the readings. And here is the problem

Screenshot_20180402_152831.png (82.57 KiB) Viewed 4247 times

All readings are in Celsius
t_of is the internal sensor
t_of2 is the external sensor
t_int is the ESP's temperature sensor
corrected is t_of/1.037 which i've found gives a value pretty close to the real(external) temperature. Except when both temps are rally close.
As you see the internal readings are always higher. The box is placed with the ESP32 upside so the hot air goes up. The internal readings are also "sharp". Obviously the biggest problem here is the air circulation.
Does anybody have a similar project? Could you give me some tips for this situation? I know the internal temperature sensor of the esp cannot be trusted but sometimes it reaches 46C and setting the wifi to esp_wifi_set_ps(WIFI_PS_MODEM) doesn't help.
Im working on a deep_sleep variant but the CSS811 lib re-initializes and resets the sensor after every wakeup so it cannot pass the 20minute calibration .

Thanks!