Smartphone magnetometer for DC current measurement

[babysitter]

Hi,

today my lazyness prevented me from grabbing a digital multimeter when I was curious if a switched 10A DC circuit is on or off.
Considering how Lord Kelvin and the other great old guys measured DC currents, i popped out my mobilephone, set it to the field test mode and wanted to see if the current causes a visible result.... it does.

Field test mode of Samsung phones can be summoned up by entering *#0*# into the phone app.. then select "Sensor" and watch the three components of the mag sensor.

I was able to see the switch state, my curiousity was satisfied.

At home I made a little video, showing the effect:

https://youtu.be/oSH31KV1ODg

This way, one can indicate a current.

Refining the method, e..g using a fixture for orientation of the mobilephone sensor regarding earth magnetic field and wire, could allow some basic measurement. I have just put my phone on top of a sealed lead acid battery and was able to monitor the relative current during discharge. A dedicated app, using the X Y and Z component and a multiplier and offset value might be a nice tool - interested, anyone ?


Best regards
Hendrik

P.S.: Yes, I see that the compass needs calibration, too.