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Registered Member #503
Joined: Sun Nov 19 2006, 06:37PM
Location:
Posts: 59
Hi ,
I could do with some help on DC current measurement. I need to measure a current of maximum 300mA which is on a common mode voltage of 30VDC.I was planning to use a 3 - OpAmp differential circuit using OP07. This does not seem possible now because I find that one of the differential inputs has to be grounded.The ground of the measuring circuit shares the same ground as the current circuit. ( I hope I put that meaninfully.) Is there any other way to do it without using special ICs from Linear or AD. Google provides mostly links to these. Can anyone suggest/point to some links which would help me.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
What's wrong with special ICs? I stumbled across this article the other day, which recommends the AD8210. I'm sure you could get samples from Analog.
You could make your diff-amp thing work with a precision voltage divider, or use a sense amp based on a LF411 or TL081, which both have a common-mode input range including their positive supply rail. (I hope you know what common-mode input range means, or you're in for some interesting pitfalls in this application.)
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High side current sensing
