Quote:
Originally Posted by lemon1324
Those work by measuring voltage generated in a coil of wire wrapped around the wire you're trying to sense. To induce this voltage, you need an AC signal in the wire who's current is being measured.
The motor controllers output a pulsed DC signal though, so they may work (Our mentor was formerly a EE prof, and thinks pulsed DC may work through a coil of wire for sensing). We haven't tested this yet.
There are also hall effect devices that measure the magnetic field generated by the wire (and work for DC applications) and I think you can get a hall effect IC for ~$2-5
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You will get an output from the pulsed DC, but I think it will be more of a pain to use than it is worth. I'd use this approach for measuring commutation, not current - each time the brushes hit the next coil, a small current pulse is created that could be detected with this coil. The number / rate of pulses tells you distance / speed of the motor.
For nasty high currents I've used this guy:
http://www.gmw.com/magnetic_sensors/...csa/CSA-1.html
The eval board can be zip tied to a wire and get reasonable results. My interns used this in the battery monitoring board they developed to help characterize loads the PD would experience.