AVR-Chat

Hi
  well one approach is to use one power supply for your OpAmp and ADC.
  this powersupply should be isolated from the 70V voltage and from other digital circuits you have.
  well now the ADC will generate the correct value but the 0V and 5V of the ADC output is based on its own GND which is different from your other logic devices.Then you have to use an optoisolator (ON3131 or ...) for each bit of you ADC so you will have 8 OptoIsolators for a 8bit ADC.
  Thats all.
   
  M.Mashaghi

magzky02 <magzky02@yahoo.com> wrote:
          Hello all,

I am going to measure the current (0-500mA) on a system. i will be 
using a current sense resistor, and an op-amp then i use ADC to 
measure the opm-amp output. But my problem is that the the line is 
high voltage (70 V). I am thinking to isolate the ground of the the 
line and the ground of my monitoring box. In this case, the monitoring 
box will not sence the 70 volt line as 70 volt, but will just measure 
the voltage drop accross the current sense resistor. A idea on how to 
measure current on high voltage systems is highly appreciated?

regards,
mago



         

       
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