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Topic: Current measurement on positive or negative side? (Read 1 time) previous topic - next topic


Look up Kirchhoff's current law, Current will be the same whatever side you put the sensor, assuming it doesn't branch off at some point. Make sure you put it in series!


Thank You, I thought so, but it's nice to be sure. I'll probably need to read up on my electrical basics :)


Feb 14, 2013, 04:02 pm Last Edit: Feb 14, 2013, 06:19 pm by jonisonvespaa Reason: 1
bloody hell 130a dc be careful with that, i used to work on lifts with very big dc generators scary stuff.


Feb 14, 2013, 09:11 pm Last Edit: Feb 14, 2013, 09:19 pm by Docedison Reason: 1
I realize it is counter intuitive But I'd place the sensor in the high side of the motor... because of the possibility of a failure in the power connections to the sensor or the sensor proper. If low side sensing fails then you  have full supply voltage on the ground leads.. If high side sensing fails you have no power to the motor, much easier to troubleshoot and much safer to work around. This is one of the reasons why switching grounds is not wise unless it is an absolute last resort -- do-able but inadvisable. Supplies may be switched but it is Always a last resort to switch or sense ground in any high voltage control circuit.
The Allegro ACS series current sensors have a 2KV isolation barrier between sense and sensed conductors so there should be no issues of that nature in using the sensor in the high side of the motor power circuit.

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There is little risk of personal injury, as the system is only 24 volts. But I see your points about troubleshooting and also it makes sense to not have permanent power on ground leads. I will have to find the best compromise between physical layout, possible interference and safety. Thank you.

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