ADC Calibration

Sven

Hello all.
I'm trying to build a voltmeter for the windmill. (I live off grid)
I have followed the instructions in the Basic Analog Digital manual but I can't seem to get the ADC to display the correct voltage as a DMM.
If the 10k pot is adjusted to 5k ohms the ADC should read 1111000, not 11100000. Voltage measured with the DMM will show half of the supplied voltage, but the ADC will read a much lower voltage.
This is built on a breadboard. Is a deadbug construction a better idea with shorter wire leads?

Any ideas?
I'll try and reply in a timely manner but Internet is pretty spotty for me.
Thanks
Sven

stamptrol

Hi Sven,
Welcome to the forums.

With only 7 bits of conversion, your ADC will be giving you a pretty coarse measurement, which may be part of the problem.

Also, you don't tell us what the voltage is going into the 10K pot. Many ADC's are designed for 0-4.096 volts in or some other range and that may affect the conversion. What ADC are you using?

Cheers,

Sven

I'm using the ADCO831. The Voltage is 5V off the BS2 Project board.
Does that help?
Eventually I need to measure voltages up around 15+ V

Sven

Moskog

Another way of measuring voltages can be found at Tracy Allen's web site Monitoring battery voltage using RC-time.
A very simple way that works pretty good without using ADC, just a couple of resistors and a capacitor.

Sven

Hey, that's a good site. Thanks for the update.

I've been playing around with the ADC some more and I have got it tracking within .25 volts. So its not great, but much better than it was.
I'll try the RC- time idea and see if that works for my project. Besides, I have the parts to try it and I don't have a higher voltage ADC yet.

The sun is out and the wind is blowing. So I get to use the computer today! ya!
Again, Thanks for the help

Sven