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Does a capacitor charges smooth, or in stairs?
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StillTrying:

--- Quote from: rhb on June 07, 2020, 05:45:46 pm ---Would you post a schematic of the setup you used?
--- End quote ---

There's not a lot to it! The 5V square is from the same thing I was using to apply 1us pulses to 5mm LEDS, the 390R was the first one I picked up around 500R, and the coax just happened to be ~2.5m long.
There's no GND wire or clip on the X10 probe (SP) at the coax, just the GND ring resting on the 25mm of shield and the probe tip resting on the 390R and core junction.
Captured at 5 Giggle Sa/s I don't think there's any scope ringing in the yellow waveform, I think any ringing is real coming from the large amount of real 68MHz ringing on the 5V square.
Labrat101:

--- Quote from: StillTrying on June 07, 2020, 10:06:46 pm ---
--- Quote from: rhb on June 07, 2020, 05:45:46 pm ---Would you post a schematic of the setup you used?
--- End quote ---

There's not a lot to it! The 5V square is from the same thing I was using to apply 1us pulses to 5mm LEDS, the 390R was the first one I picked up around 500R, and the coax just happened to be ~2.5m long.
There's no GND wire or clip on the X10 probe (SP) at the coax, just the GND ring resting on the 25mm of shield and the probe tip resting on the 390R and core junction.
Captured at 5 Giggle Sa/s I don't think there's any scope ringing in the yellow waveform, I think any ringing is real coming from the large amount of real 68MHz ringing on the 5V square.

--- End quote ---
I did not use the inverter I just connected in series but got the same results as you.
but if you turn on the FFT you can see there are aliases . If you use a 50 cable it must have the same impedance as the scope or you will see all sorts of weird stuff .
My cable was 56ohm when matched it lost all the steps you are not seeing what you think .. Its late we are 2 hrs different  tomorrow . also Dave did some videos on this sort of thing its distortion call what you like but its not
due to the charging effect.
StillTrying:

--- Quote from: Labrat101 on June 07, 2020, 09:35:10 pm ---I am not knocking your work or the scope picture it was good .  :-+
--- End quote ---

Knock all you like, it was just a 5 min. experiment. :)

I can't see any images in your post, or even find links to any in the html.

Yes it's just a transmission line rather than a capacitor.
Vid from previous page https://youtu.be/gdiPwbZm0aM?t=2256
T3sl4co1l:
Now consider what happens when:
1. Transmission line impedance is very low, and length is very short.  This is roughly descriptive of typical film and ceramic capacitors, where layers are stacked or rolled up, and the ends are shorted across; the electrical length is approximately the component length, no more.
2. Connecting leads or traces have high impedances, and comparable lengths.
3. When these TL segments (such as they can be considered to be) have high HF losses, so that if any oscillations do appear, they dissipate quickly.  What does it mean for a "wavefront" event to dissipate?!
4. When the signal source and/or scope have much less bandwidth than the electrical lengths in #1 and #2.

The TL model doesn't go away, it just becomes more complicated; and potentially less useful -- instead of tracing one seemingly discrete event back and forth (like for the one-end-driven TL stub), there are myriad reflections to keep track of, and the slow-moving signal can no longer be considered as a discrete wavefront, but must be handled as a continuous, tsunami-like flow of charge.

In general, we can split a connection into two ports of some impedance, and consider the incident and reflected waves.  Which are no longer discrete wavefronts, but themselves continuous functions of time -- waveforms, just like any other.  This leads to peculiar cases, like a loose battery forever transmitting continuous power, only for that power to immediately and constantly reflect back, in phase, to the battery, hence deliver no charge.

This is a perfectly equivalent description of current flow, and an interesting one to wrap your head around!  Thought-experimenting with ordinary cases like DC and mains power supplies, is useful for practice itself, if not very useful for practical calculation. :)

Ed: typos

Tim
rhb:

--- Quote from: StillTrying on June 07, 2020, 10:06:46 pm ---
--- Quote from: rhb on June 07, 2020, 05:45:46 pm ---Would you post a schematic of the setup you used?
--- End quote ---

There's not a lot to it! The 5V square is from the same thing I was using to apply 1us pulses to 5mm LEDS, the 390R was the first one I picked up around 500R, and the coax just happened to be ~2.5m long.
There's no GND wire or clip on the X10 probe (SP) at the coax, just the GND ring resting on the 25mm of shield and the probe tip resting on the 390R and core junction.
Captured at 5 Giggle Sa/s I don't think there's any scope ringing in the yellow waveform, I think any ringing is real coming from the large amount of real 68MHz ringing on the 5V square.

--- End quote ---

Where was the source, where was the resistor and where was the DSO on the transmission line?  I've got  sources which don't ring so badly.  The 11801 calibrator at <20 ps rise time, the <40 ps Bodnar  BNC pulser and a Tek 7104 to check them against :-)

Reg

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