Hello folks.
I'm tackling a small project (I think) to convert the signal from the back of a Yanmar tachometer into something that I can safely feed to an ESP32, and then convert it to a NMEA0183 sentence. When I attached my HDS1021M-N to the back of the tach, I got a good indicator that the waveform is in the low kHz range, but there are some nasty voltage spikes that might exceed the tolerances of the ESP32, and I don't want to let the magic smoke out.
To that end, I built the attached circuit (courtesy of my father checking one of his radio newsletters, because none of the ones I could find on various websites that claimed to be about circuits worked) to give myself a basic sine wave. This circuit works just fine, converting the 6V input to a ~350mV wave at ~1 kHz. The precise voltage and frequency aren't too critical for my testing, so long as they're within the bounds of what the tach spits out.
My next goal was "rectify it to simulate how I can clip out the spikes from the tach". To that end, I placed a single 1N4148 diode after the cap leading to Vout.
What I'm not undestanding (and my electronics knowledge is rusty, because I last used it about 20 years ago in college) is why I'm not seeing a waveform that shows a more pronounced clipping of the wave (either the +ve side or the -ve side). The 'scope is showing a wave that's very close to the original wave, with a slightly more rounded appearance on the "clipped" side of 0.
Dad sent me a photo of his cheap scope hooked up to the same circuit, and he's getting a waveform that's much flatter than mine.
On the assumption that I haven't messed up the circuit somehow (and we agree on the unrectified waveform appearance and values), am I experiencing a limitation of this 'scope?