thanks guys,

I am on a completely different lead.. actually i am measuring the voltage drop on the battery, amplify the noise, and make an FFT on the amplified noise, and detect a recurrent voltage drop that happens always at the same frequency, with corresponds to my load which is triggered at 1.48 Hz.. seems to be working pretty well....

__________________
Ibrahim Kamal
check my electronics and robotics page: http://www.ikalogic.com/

 

Your pulling my leg, right? How can taking the FFT of a signal be a simple, low-cost way to measure the current?

__________________
Carl

 

Maybe with an oscilloscope whose cost is not being accounted for?

 

Well, he talked about a "low cost solution" and a yearly production of 180,000 parts so I just assumed (incorrectly apparently) that an expensive instrument that measures FFT was not in consideration as a possible solution. Heck, he can buy a DC current probe from Tektronix for a few thousand bucks (US) that'll do the job too.

Apparently this is for a production test and not some device that is built into the unit, but we we never told that. It's a waste of time for the rest of us if some ----- does not tell us what he really needs and we go off on a solution tangent.

__________________
Carl

 

I assumed he's going to take the noise on the supply (assuming that the supply impedance is predictable enough), amplify it to meet the uC's input requirements, and do a one-frequency software fft.

 

As far as I can remember from physics, a hall effect sensor is a very thin square of gold which you put a current across. The magnetic flux then distributes the electroncs in a non-even patten. (It's been a while since I had Physics lessons.)