ADC conversion trouble

[HenrikOlsson]

I guess it depend of the accuracy you need. If you use the internal Vref, when the PSU voltage swing, your accuracy will swing with accordingly right?

Yes absolutely, but if you have 20mV noice or swing on the supply rail with a sensor output of 10mV/° you have 2° worth of noice. If you boost the signal to 100mV/° the same noice on the supply rail is now "worth" 0.2° instead.

PICante,
In a previous reply I sugested a Vref of 1.024V but after reading the 16F88 datasheet that may not have been a very good advice. Vref needs to be 2V minimum according to the datasheet so keep that in mind if you go for an external reference.

/Henrik.

[PICante]

Thanks guys!

Yes I like to try the external reference and I need one decimal accuracy with +- 0.5C overall. Maybe it will take a high stability voltage source to reach this.

Now I will try to figure out how to connect the Vref + & Vref- also how to set the bits in ANSEL and ADCON1 perhaps even the CVRCON? Not easy being a newbie! :-)

[mackrackit]

Not easy being a newbie! :-)

I know what you mean. But it makes for a good excuse when something does not work or the room fills with smoke!!!

[mister_e]

But it's always fun once in a while to have a smoke show huh?

[mackrackit]

Then you tell the kids. "I just did that so you could see what not to do." and "Always wear your safety glasses while programming."

[mister_e]

Don't try it at home, i'm a professional

[PICante]

Thanks guys, you are a lot of comfort!

Unless you see a powerful light at the horizon I’ll be back soon!