temperature sensors(Hi Sid)

Archiver

Good morning Sid,

You're correct, the 4096 counts a 12 bit ADC offers would offer
considerably more resolution. Howwever, consider the 255 counts of
an 8 bit DAC. If the LM34 output is scaled to utilize the entire
range of the 8 bit ADC then you're left with better than 2 counts per
degree F, which exceeds the stated design requirements. This scheme
would work fine, if you're not interested in reading more than 125
deg F. The 12 bit ADC would be easier to use, (scaling not necessary)
and would offer greater resolution. Again, you are correct.

It always comes down to the same thing for me: cost. Have you
purchased a 12 bit ADC lately, they are just a bit pricey. The 8 bit
ADC will meet the design requirements, at substantially less cost.

Best Regards

Rich AA2DN

In basicstamps@y..., Newzed@a... wrote:
> For Rich
>
> At about 100 degrees F. the LM34 puts out a raw count of about 850
which
> converted to millivolts is about 1010. The highest count you can
get with 8
> bits is 255. I use 12 bits to get the full count.
>
> Enlighten me, please.
>
> Sid - W4EKQ