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

Yeah, but they are only digital, expecting digital type pulses. I'm
thinking of a similar current tracer arrangement, but analogue. I don't
know if it would be possible to hack the current tracer probe to get an
analogue output. I can't remember if it uses a hall Effect device or a coil
to sense the current, it may even be a combination of the two.



On Sat, 4 Jan 2025 at 07:57, David VanHorn <[email protected]> wrote:

> 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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