Hi there. Whoa! This has sat around for a while! Sorry about that. I've just moved countries and started a new job, so life has been pretty busy!

So, it's pretty easy to knock something up on the bench - but hard to make something well behaved. If you have a need for something I would suggest an off-the-shelf Hall Effect sensor. These can be purchased from the usual suspects and can achieve gain/inearity accuracy of 0.1%, DC offset of 0.5% (can be calibrated out) and DC drift over temperature of 0.5% (cannot really be compensated out).

I do intend to get back into this project moderately soon.

Is the above practical to build? Will it work under varying circumstances? I am looking at a solution to measure AC and DC current. Typically the frequency can vary between 0 and 5Khz. The current can vary between 0 and 10A