ADC lcd display help

[Charles Linquis]

Correction:

12 bit A/D count = 4095 when Vin = Vref

[kevlar129bp]

Thanks Charles,

I think I grasp that concept.
350/1024 = .3418 ... so for every .3418 volt change at the 350 side of things, there is a "count" change.
Therefore, if we start with, say:
165 vdc
...through the voltage scaler to the ADC in:
165/70 = 2.3571 vdc
VRef(5.1)/1024 = .004883
2.3571/.004883 = 482.7115 <<<<<<<<<<<<<<<<<<< The ADC "count" would be 482?
(ADC count * 4883 * Scaler ratio) / 10000
(482*4883*70) / 10000 = 16475.242<<<<<<<<<<<<<<<<< 16475 is the "high voltage"?
...for the lcd:
LCDOut 16475/100,".",16475//100," VDC"
"164.75" <<<<<<<<<<<<<<<<<<<<<<<<< Where did I go wrong in not getting "165"?

I am probably confusing myself more than I'm helping.
Would love a quick tutorial from one of you knowledgeable folks.

Thanks again,
Chris

[mackrackit]

At the risk of confusing you more...
http://www.picbasic.co.uk/forum/cont...Sensor-Scaling

[kevlar129bp]

Thanks Mack,

Funny you point out that thread... That's the one I've been racking my brain over.
I'll take another look though.

Chris

[kevlar129bp]

Hey Mack,

Quick question. When we're talking about the ADC count based on the sampled voltage,
what happens to the count when it's fractional?
IE:
count = 557.26 ... does this become 557 or 558?
count = 952.76 ... does this become 952 or 953?

I guess I'm just wondering what the "rounding" routine is, if any?

Thanks again,
Chris

[mackrackit]

http://www.picbasic.co.uk/forum/show...7177#post87177

[kevlar129bp]

Thanks for the heads up Mack,

I guess I was a bit confused by this in your ADC scaling tutorial:

Convert this to an 10 bit PIC® resolution.

10 bits ADC = 0 to 1023, 1024 steps.
At 5.0 volts one volt of input will will read 205. (204.6 actually)

Why would that read 205, instead of 204?
Thanks Mack, for helping a newbie trying to understand.

Chris