On Thu, Jun 27, 2002 at 10:22:42PM -0400, Brandon Stewart wrote:
> What is the purpose of having this Vref?  Why not use the internal 5V
> reference all the time?

Two reasons: Narrow the range for better resolution and to ease the process
of conversion.

>  If it is for accuracy reasons, then if your 5v line
> goes wacky... then can you count on the PIC during that time anyway?

Doesn't matter.

Here's a quick example: Say the range of what you're measuring goes from 0V
to 4V. So you use a 4.096V reference. You get 3 instant effects:

1) You get nearly full range on your conversion: 0..1000 instead of 0..820
2) You get a smaller voltage step between steps (0.004V vs 0.0048828125V) and.
3) You get a much easier conversion since the steps are exactly 4 mV each.

Hope this helps,

BAJ

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