EM voltage detection circuit

Hello everyone. I am trying to measure / sense ChipSHOUTER pulses without a scope (more accessible), but would also be interested in what you guys think is a good circuit for picking up the pulses with an oscilloscope. As I’m a computer scientist and not electrical engineer, my physics and electronics skills are very limited, as you’ll see shortly… :smiley:

The idea is installing a coil of wire acting as an inductor on the XYZ table, permanently, and using it to measure the magnetic field of ChipSHOUTER hovering above it. By measuring where the magnetic field is strongest, the tip can be accurately zeroed / “homed” and a glitch could be reproduced more reliably after replacing or changing tips, shutting down the table or even working on a different target for a while (as long as the target is also put back accurately of course).

I can only post a single picture, so here are 3 circuits which I’ll reference shortly.

For now, I tried this circuit and it works fairly well, but of course it doesn’t hold the voltage long enough and stable enough to reliably read it with an ADC.
(Circuit number 1)

I am not entirely sure about the first resistor but the cap and output resistor should be correct.
On my scope I measure a typical capacitor charge and discharge graph.

I am considering just keeping this circuit and reading the scope data through USB, but I’d prefer to be able to sample it using a microcontroller that can feed it back to the CNC’s control board or the host PC.

The following circuit was my next idea; a simple peak detector hooked up directly to the coil, but it’s not really working, although I only tested it on breadboard so far. Before I solder and try it again, maybe someone can give me input on this.
(Circuit number 2)

Maybe I should just put this circuit (which with a regular analog signal seems to work) behind the first circuit instead of hooking it up directly to the copper wire coil / inductor, something like shown here?
(Circuit number 3)

Any input is highly appreciated, thanks in advance!

Problem solved! Circuit 2 works perfectly fine, I just had a wiring issue.

Good to hear you got this working, Dave.

If you’re interested, our Discord server tends to be a little better for more general/open ended questions like this: ChipWhisperer Chat