Re: [EE] measuring the magnetic field from a small trace carrying a < 50uA load?

I think I would be inclined to see if I could fine a linear Hall Effect
device in an SOT23 package and make my own current probe. Such a package
would be small enough to hold against the smallest of tracks to sense low
currents without having to cut tracks.



On Fri, 3 Jan 2025 at 17:56, smplx <[email protected]> wrote:

> Thinking about core memory: how about using a small ferrite core with a
> sense wire and write wire through it. energise the write wire to set up a
> field in one direction then bring the core next to the trace and measure
> how long it takes to switch magnetic field direction. or maybe how much
> current you need to apply in the other direction to change magnetic
> polarity. or something like that. you'd obviously need to calibrate your
> probe against known sources. Look at how small ferrite cores were (towards
> the end of their reign) and how little current they used to change state.
>
> Regards
> Sergio Masci
>
>
> On Fri, 3 Jan 2025, Chuck Olson wrote:
>
> > Do you have an old busted cassette recorder ?  Maybe the playback head
> > could be used to sense the field ?
> >
> > On Thu, Jan 2, 2025 at 7:05 PM Jason White
> > <[email protected]> wrote:
> >>
> >> When developing battery powered devices, sometimes it can be difficult
> to
> >> track down where the last few dozen microamps of load are being drawn.
> >>
> >> One can resort to systematically cutting traces and desoldering
> components.
> >> But that is destructive, labor intensive, and error prone.
> >>
> >> I would like to know if an active probe exists that can measure and
> >> discriminate the current/DC magnetic field of small < 50uA loads on
> small
> >> but loosely packed PCB traces.
> >>
> >> Are there other viable (hopefully nondestructive) ways to track down
> small
> >> loads? (A low noise thermal camera in a vacuum chamber?)
> >>
> >> --
> >> Jason White
> >> --
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