DS18B20U shows -37 degrees at room +24

Hi @antons15 I have test your sketch :

Results :

Requesting temperatures...
Temperature for the device 1 (index 0) is: 28.00
Requesting temperatures...
Temperature for the device 1 (index 0) is: 28.00
Requesting temperatures...
Temperature for the device 1 (index 0) is: 28.00
Requesting temperatures...
Temperature for the device 1 (index 0) is: 28.00
Requesting temperatures...
Temperature for the device 1 (index 0) is: 28.06
Requesting temperatures...
Temperature for the device 1 (index 0) is: 28.00
Requesting temperatures...
Temperature for the device 1 (index 0) is: 28.06

....

The temperature here is 28.xx now.
I have use MEGA.

I think your sensor is measuring your hand temperature.

RV mineirin