EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: JPortici on September 30, 2017, 04:57:11 pm
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Hi,
i've been scratching my head a bit today on this one:
I want to measure the current on a bipolar power supply, using those theap INA current sense amplifiers from texas.
positive voltage rail, that's easy, follow the datasheet.
negative voltage rail, ehr not so easy. Common mode range goes from GND - 0.3V to 26V.
If i had the sense resistor on the GND side it would be easy, common mode is inside range, but that would be pretty impractical (basically have two grounds.)
What can i do then?
I've seen some solutions, suggesting to use the negative rail as virtual ground, generating a local 5V difference using a zener and then apply a black box (kindly left as an excersise to the reader) to shift the voltage up to the 0-5V range.
makes sense, should work, but the simulator though doesn't agree and i don't have the parts to test it in the real world.
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Not sure but seems if your load Rsense to ground is cut to a value such
that Iloadmax X Rsense > -0.3V it should work ?
So if load is max 10A, then Rsense <= 30 mohms ?
But then there is this - http://e2e.ti.com/support/amplifiers/current-shunt-monitors/f/931/p/616053/2269385 (http://e2e.ti.com/support/amplifiers/current-shunt-monitors/f/931/p/616053/2269385)
Regards, Dana.
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But as i said i don't want to do that. Resistor has to be on the -12V side, current is 600mA max