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

Ingo Debus igg.debus at gmail.com
Mon Jan 17 18:06:03 CET 2022



> Am 14.01.2022 um 05:10 schrieb Paul Perry via Synth-diy <synth-diy at synth-diy.org>:
> 
> I'm not an EE, but one thing I have noticed is that the people who design the chips think in terms of current, and the people (like me) who use them, are likelier to think in terms of voltage. Not that it matters, since V=IR. Probably base amateurs like myself think of voltage because it is easier to see on scopes and meters.

Yes, probably because it’s easier to measure voltages than currents. For current measurements usually a wire or trace has to be cut. That’s often difficult or even impossible (think multilayer PCBs).

Thinking in terms of voltage is also reflected in the traditional way schematics are drawn (i. e. the way we all usually draw them). If three points (components) A, B and C are to be connected, it’s perfectly legal to draw either A—B—C or A—C—B, even if it is important that, say, B is in the middle (think rectifier - filter cap - load in a power supply for instance). Since both ways to draw these connections are equivalent, PCB design software cannot tell the difference (at least I don’t know of any software that does), so doing a good PCB layout is so much more than just translating the schematics. Maybe it wasn’t if there was a more appropriate way to draw schematics?

I had these ideas first when I did some measurements with this gadget:
https://www.aimtti.com/product-category/current-probes/aim-i-prober-520 <https://www.aimtti.com/product-category/current-probes/aim-i-prober-520>

Measuring current is simple this way, but first you have find the places where to measure which can be tricky. Sometimes the line on the schematics simply does not exist on the PCB.

Ingo

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