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

Hp did that current pulser and tracker probe set.  On ebay sometimes.

On Fri, Jan 3, 2025, 3:11 PM Alan Pearce <[email protected]>
wrote:

> 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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