[sdiy] Voltage vs current, was Low voltage synthesis?

cheater cheater cheater00social at gmail.com
Wed Jan 19 13:20:07 CET 2022

On Tue, Jan 18, 2022 at 2:54 PM Ingo Debus via Synth-diy
<synth-diy at synth-diy.org> wrote:
> Am 18.01.2022 um 09:25 schrieb cheater cheater <cheater00social at gmail.com>:
> jesus, that's a grand for a probe. but it's no contact, so that's
> nice... how does it work?
> You can spend much more for a current probe.

I bet!

> Quote from the instruction manual
> (https://resources.aimtti.com/manuals/I-prober_Instruction_Manual-Iss7.pdf, introduction, on page 2):
> "This current probe employs a sensing method generally known as a fluxgate magnetometer, and
> measures the magnetic field surrounding the electric current. The magnetometer consists of a small
> coil of wire surrounding a core made of an advanced material with special magnetic properties. An
> excitation current (at approximately 40MHz) is passed through the coil, which magnetises the core
> alternately in opposite directions. If there is no external magnetic field, this magnetisation is
> symmetrical. When an external field is applied, the resulting asymmetry is detected by a feedback
> loop which applies an opposing current through the coil to restore the net field to zero. The output
> voltage is proportional to this opposing current, and therefore to the magnitude of the field“
> Ingo

The explanation is kind of spongy... Are they measuring the B-field
around a wire? As in what's explained here:


In that case, does the measured value depend on the angle of the probe
vs the conductor? It feels like it should.

Does the probe provide absolute amplitude measurement, or is it purely
a relative amplitude measurement device? I.e. will 2A in the circuit
always be, say, two div on the scope, or will it change, but the shape
of an AC signal will be mostly the same?

Is this probe "just" a very tightly wrapped coil of (gold?) wire in
the tip + an auto-gain compensation circuit in the handle? Feels like
we should be able to recreate that...


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