SHT31-D and BMP280 heat themselves up when in operation

[ceoloide]

Hello,

I purchased an SHT31-D sensor breakout board and a BMP280 breakout board and I've wired them following the website instructions to an Adafruit Feather M0 + WINC1500.

What I've noticed, after reading weird temperature values, is that the two sensors appear to be heating up! From a pure sensor reading, having the sensors placed close to each other and with no change in air temperature, the measured temperatures start to drift up until they level off at around 27.5-28C, with room temperature possibly 25.5C.

By chance, I happened to turn on a fan nearby, and the temperature dropped and then stabilized at around 25.5C, which is the presumed room temperature (read from 3 different sensors, integrated in other products I own).

Based on my rusty knowledge of physics, a fan won't be able to cool down anything below room temperature, since it just moves around air, and assuming a large enough room with a consistent enough temperature throughout (which is my case). In fact, the other three sensors do not change temperature at all when exposed to the fan for large periods of times. Considering that the 2 degrees C are gained over a few minutes immediately after I turn off the fan, I started to suspect that something might be heating up these sensors when in continuous operation.

Is this a possibility based on the breakout design? Is it because of how the sensors are driven? Am I going crazy?

Thank you for your help,

Marco

[adafruit2]

these sensors self-heat. there's not a lot you can do about it without in-depth library hacking (our libraries dont support sleep modes), you can just account for it by subtracting a few degrees

[lacibaci]

I noticed a similar behavior on my SHT31-D. In rest it will read about +5F. As soon as I turn the fan on it, it will report correct temperature. I am waiting for another one to compare, but if this is the intended behavior, I'm going to have to return them. I didn't see this mentioned anywhere in the specs...

[adafruit2]

for the sht31 it has a heater inside, make sure that's off?

[lacibaci]

Yes, I did make sure that it was off. BTW, I did notice a few other posts with exactly the same behavior - not sure why this happening. From the spec sheet they do mention an internal heater but it shouldn't turn on on it's own.

[adafruit2]

:/ yeah we dont have any insight into the internal temperature regulation, but chips do self heat, people often put them into reset/off mode to avoid it

[lacibaci]

I sent a message to Sensirion Dev support. I'll post back if I get a reply.

[adafruit2]

yes! thanks!

[lacibaci]

Just received a reply from Sensirion support and it indeed looks like the sensor was out of spec. Thanks to Adafruit for sending a replacement.
I have another thread here: viewtopic.php?f=19&t=142238 where I compared seven SHT31 sensors.