Static fields can be measured with a field mill as illustrated below. I was reminded of condenser mics with their fragile little MOSFETs as far as AC detection goes. With proper bias, suitable MOSFET an a hatched zone on a 1-layer PET PCB acting as the sense electrode, it should be possible to pick up AC components of the electric field.
Charge detection will be limited to low frequency AC, but I imagine it to be usable.
@MisterHW@fosstodon.org It would be neat to just have a fluid to dunk the pcb into tho. use a probe to hilight a node.
@RueNahcMohr@infosec.exchange guess you'll be SOL there, unless you find deposition of ultrafine particles approachable. I've seen them trace out 3.3V lines on a PCB, with the rest remaining clean.
@MisterHW@fosstodon.org homogenous led dies in a clear semiconductor fluid?
@RueNahcMohr@infosec.exchange okay, but in more practical news:
when those 128x32 OLEDs became popular some 10 years ago, a friend and I strapped one to a pen, ESP8266 and sm0l battery.
We got to the point where the display would show a datamatrix code encoding local measurements. We should have used something with a better finder pattern, but the idea was to add 6 DoF tracking, and then one would scribble across a PCB with an H field / E field probe stylus and image analysis software would reconstruct that.
@RueNahcMohr@infosec.exchange I still think it's a cool idea, since you could basically even capture waveforms, analyze them and then 3D plot the spatial distribution of fields and spectal components of noise from DC to RF.
Someone should finally steal that idea and make it happen :)
And probably there are also better ways to do the tracking (e.g. sub-mm UWB + IMU?)
@MisterHW@fosstodon.org I just want to know where the node turns up... even if its a 10 layer board...
@RueNahcMohr@infosec.exchange "just" means you'll stick the PCB in your 3D printer, mount a pogo pin as a tool and poke everything pad-shaped
don't look at me like that, I don't make the rules
Rue Mohr