That’s interesting. The temperature and humidity values on the website are more or less correct for me, whereas if I use the equations in the SHT21 datasheet (like you have done with the temperature) and print the calculated values through Serial, I typically get a temperature 5 °C greater than the actual temperature and a humidity value about 15% less the the actual relative humidity as measured via 3 different hygrometers that I own. This leads me to believe that the website is doing calculations other than what the datasheet mentions. In fact on GitHub there is a file called sck_sensor_data.php that gives different calculations than the SHT21 datasheet:
public function tempConversion($rawTemp)
return round(-53 + 175.72 / 65536.0 * $rawTemp, 2);
public function humConversion($rawHum)
return round(7 + 125.0 / 65536.0 * $rawHum, 2);
Are these equations used on the production website? Why don’t they match what’s in the datasheet? I haven’t come across any information that intimates that the SHT21 needs to be calibrated so one would think that the equations in the datasheet would be sufficient. Are these parts acquired from reliable sources? I ask because bad sensors seem to be the cause of bad readings and it seems that one can still acquire such bad sensors for less money.