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pcaffalldavis Senior Member Joined: 17/10/2011
Location: United States
Posts: 187
 Posted: 10:40pm 13 Jan 2012

Okay, I will add resistors R2 & R3 and recalculate based on the resistors true resistance as measured using a meter.

I'm currently using 1.8K resistors for R1. Do I need to change them for 1.5K resistors or can I leave them as 1.8K? Will these 1.8K resistors affect the voltage divider formula? I don't see how they would, but I am not schooled in these matters.

The formula I will use to calculate the Pin(1) multiplyer is: 100/(R3/(R2+R3))

If R2 is 18K and R3 is 27K the result should be about 166.7, but should be adjusted for the actual values of the resistors. If I understand correctly then the degree Celsius reading would be Pin(1)*166.7-273.

Some of this was taken from Olimex's blog and repeated here for the benefit of those who didn't follow the link. Thank you Olimex

So folks, do I need to swap the R1 1.8K resistors for 1.5K resistors?

Pete in Hyder
We're all here 'cause we're not all there.