I have been using the AttoPilot 90A sensor on my 3DR quad copter, from the start. It works, even though AC firmware requires some software lines to define calibration ratios (I looking forward to that to be set in the Mission Planner configuration).
Anyway, a few days ago I read a post from Arnt-Inge about AttoPilot sensor noise was interfering with sonar signal. That got me thinking about how the Atto-sensor is installed, and I started to worry about if the black ground wire in the Atto-sensor signal cable might act as a parasitic shunt to the main battery ground lead. Simply put, the motor current and other power consumers on the copter should have their current returning via the battery pack cable, not via the tiny Atto-sensor ground wire (and the APM board cirquit).
This evening I set up a test to find out whether the Atto-sensor three wire signal cable, black ground wire, acts as a parasitic shunt or not. I simply cut the black wire and connected a low impedance digital current meter.
Test turned out positive. At rest there is a 30mA current from the APM board to the sensor ground.
At full motor power it mesures 450mA. Half of an ampere. Hmm.
For me this is slightly disturbing. Having parasitic current like this in low level signal cables is simply dirty, even though I am not sure what significant implications it has.
I would like to know what you hardware guys have to say about this, please??