Signal from car ignition coil

[ElBerto]

Hi guys, I would get signal from my old car ignition coil, here example waveform:
https://www.triumphexp.com/phile/8/227705/TEK0000.JPG

I was taking a look to similar topics:
https://europe1.discourse-cdn.com/arduino/original/4X/d/d/5/dd57d8ca064d832ab1addf6399d5adb98bf0aa9b.jpeg

but this circuit will change my coil waveform due to D4 diode (I don't understand why it's placed before D5, maybe should it placed behind....

[theeccentricgenius]

@ElBerto

but this circuit will change my coil waveform due to D4 diode (I don't understand why it's placed before D5, maybe should it placed behind....

I presume D4 is placed there to prevent inductive kick from the ignition coil.

[jim-p]

Isn't L1 a coil you wrap around the high tension lead for inductive pick-up.
There is no direct connection to the coil.

[ElBerto]

..but changing coil waveform I'll change behaviour of ignition. I don't want this.
I don't see issues about circuit simulation removing D4.

Original waveform:

D4 inserted:

[jim-p]

See this:

Reading pulses through Inductive Clamp

raschemmel: Ignition pulses are electrical. RPM is mechanical. apples and oranges There is one ignition pulse every 2 RPM, it is not as if ignition pulses are completely random. All I have to do is count the pulses. These same clamps are used in dozens of different types of automotive equipment to read RPM. They're using on dynos for an RPM signal, timing lights to detect spark and flash a bulb, etc. Companies even sell them to use with their logging software as an RPM pickup: https://ww…