How to read negative temperature with LM35?

Hi Guys,

I checked out everywhere, but there is not a single site which tells how to read negative temperatures(temperatures below 0 C) from lm35..

Thanks
SANJAY

You read it the same way as any other temperature. You have to use the formula in the datasheet to calculate the temp from the voltage.

Btw, I am assuming you are trying to read deg F or C and not K.

I think the problem is that negative temperatures produce negative voltages.

Hi Sanjay,
Maybe this old forum can help you out
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1224321879
:slight_smile:

I guess that it would be necessary to connect the LM35 earth to a known voltage above the Arduino's earth, and then subtract that offset from the reading to get a signed temperature.

Actually the datasheet has the circuit for the full range reading on the bottom of page 2. Google LM35 temperature sensor datasheet.