DS18B20 in error below -15°C / 4.1°F

I’ve got a problem which drives me crazy

I need to control a refrigerating system able to reach -40°C and I thought that, due to its technical specifications, probe DS18B20 would have been proper for that aim.

I applied the mentioned indicative libraries ( Onewire and Dallas Temp.) and everything runs smoothly untill -15°C.
As the system reaches that thresold, by the way, the probe signs " error".
I’ve been searching for further infos anywhere while finding only one post saying that the problem is due to the Dallas Temp ( seems like about conversion matters) but no solutions are given.
Can Anyone help me? Did anyone experienced such a thing before? I really need to solve this problem urgently as this occurrence is preventing me to supply my customer in due times.
Thanks in advance.

What libraries are you using for OneWire & the DS18B20? (Please supply links instead of names) and it it these that supply the extracted/converted temp reading or are you rolling your own code to do that? If your own code then please also post that or a cut down version that shows the problem your having.

The -15 C “error” with DS18B20s came up some time ago in the forum and I believe it was concluded that there was something wrong with the OP’s code.

With the forum search function now more or less useless, such posts are very hard to find. Try a different library.


Here’s my two-penn’orth.
I use all the usual DS18B20 libraries (dallas temperature control, OneWire, all from examples), get a can of pipe freezer (plumber’s accessory), and you can get down to well below minus 30 Celsius, but never seen an error, even when it’s white with frost. The only problem might arise if condensation bridges the leads on a bare chip, but encapsulated ( usual Raychem self-adhesive heat shrink) shouldn’t be any trouble. DS2438 works just as well. Iffy connections are the usual suspects.