reference voltage in ADC

Guest · Posted: Mon Nov 26, 2007 5:46 pm

Hi Everyone,
I am now working on the ADC and DAC. However, I do not understand the usage of the reference voltage in ADC.
Can anyone summarize it for me?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

See libor's comments in these posts:
http://www.ccsinfo.com/forum/viewtopic.php?t=32587&highlight=vref
http://www.ccsinfo.com/forum/viewtopic.php?t=21916&highlight=vref

See Ttelmah's post:
http://www.ccsinfo.com/forum/viewtopic.php?t=21149&highlight=vref

Guest · Posted: Tue Nov 27, 2007 12:21 pm

Thanks you.

Guest · Posted: Tue Nov 27, 2007 4:39 pm

The voltage reference sometimes is not used in ADC. But, I can not think of any other situation.
Would any one please tell this to me ?
And, I heard about "reference voltages in ADC that precision is usually more important than accuracy so Vref is not always needed."
I did not understand anything from this sentence.. Would anyone please explain it to me too ?

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

Often the system using the A/D will be calibrated after it is assembled so you get a known ratio of for example kilograms to A/D counts. If the A/D reference is a little off it will be compensated for in the calibration. But if the reference CHANGES after the calibration you are doomed. Accuracy comes from the calibration process, not the reference. But precision, in this case stability and low noise, come from every part of the system including the reference.

Clear as mud?
_________________
The search for better is endless. Instead simply find very good and get the job done.