ADCin and floating point values

[Luciano]

Analog to Digital Converters (A/Ds)
http://www.facstaff.bucknell.edu/mas...es/ConvAD.html

[Melanie]

Your ADC result will have NOTHING in common with floating point. Let me explain... assuming you have a 10-bit ADC, your minimum reading will be zero and your maximum reading will be 10-bits or 1024. This maximum reading is referenced to +VRef, and the minimum is referenced to -VRef.

If -VRef is 0v, and +VRef is 5v, then 0v will equal zero on the ADC and 5v will equal a count of 1024. It goes to assume that 2.5v will be half of 1024 ie a count of 512, and 0.5v will have a count around 102...so you will have a resolution of about 5mV or 100 points on the scale.

If you change your +VRef to 0.5v (keeping -VRef at 0v), then the scale will be between 0 and +VRef for your entire 10 bits... ie, a count of 0-1024 for a voltage range of 0-0.5v (here a resolution of 500uV).

So to summarise, your ADC range is a count between -Vref and +Vref in the 10-bit (or 8-bit is you set it that way) resolution of your ADC. Thereafter you can perform some math on your ADC reading and thrrow in a decimal point to give you an answer in volts, amps, coulombs, whatever....

Melanie

[niknaksbarbeque]

Yes I was being thick, thank's very much for the replies guys, you've let me keep my hair (was slowly being torn out in clumps).