AVR-Chat

Hello guys

i have to measure a voltage using ADC and display it on LCD display or 
seven segment display. My problem is that the the voltage to be 
measured is from 0-70 volts. if i use a 2.5 voltage reference, and use 
voltage divider, i think it will not be accurate anymore because of 
resistor tolerance. any better idea on how?

regards

mago

There are a couple of ways and they are related.  You will need to use 
1% tolerance resistors or better.  It also helps if you use an OpAmp 
with a programmable gain - To set that gain you'll need to use precision 
resistors again.  This is the only path to success - precision 
resistors.  To get higher resolution without spending huge on .1% or 
better resistors you can consider a higher AVref voltage.


DLC

magzky02 wrote:
> Hello guys
> 
> i have to measure a voltage using ADC and display it on LCD display or 
> seven segment display. My problem is that the the voltage to be 
> measured is from 0-70 volts. if i use a 2.5 voltage reference, and use 
> voltage divider, i think it will not be accurate anymore because of 
> resistor tolerance. any better idea on how?
> 
> regards
> 
> mago
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 

-- 
-------------------------------------------------
Dennis Clark          TTT Enterprises
www.techtoystoday.com
-------------------------------------------------

magzky02 wrote:
> Hello guys
> 
> i have to measure a voltage using ADC and display it on LCD display or 
> seven segment display. My problem is that the the voltage to be 
> measured is from 0-70 volts. if i use a 2.5 voltage reference, and use 
> voltage divider, i think it will not be accurate anymore because of 
> resistor tolerance. any better idea on how?

Add a trimpot in the resistor divider. Measure a voltage and adjust
the pot until the reading agrees with a 4-digit multimeter.

ohh.. This is a simple solution. thanks for the idea...
   
  cheers
   
  mago
  
Russell Shaw <rjshaw@netspace.net.au> wrote:
          magzky02 wrote:
> Hello guys
> 
> i have to measure a voltage using ADC and display it on LCD display or 
> seven segment display. My problem is that the the voltage to be 
> measured is from 0-70 volts. if i use a 2.5 voltage reference, and use 
> voltage divider, i think it will not be accurate anymore because of 
> resistor tolerance. any better idea on how?

Add a trimpot in the resistor divider. Measure a voltage and adjust
the pot until the reading agrees with a 4-digit multimeter.


         

       
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