Wanting to make some negative DC to watch conventional current flow

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I wanted to get my hands on some negative DC and see (ok we know it will  ) if it would pass through a diode from the cathode side

The first "circuit" I came up with in the midst of drawing it I thought oh wait this is gonna be a normal circuit we are just looking at it from another perspective but then I realized yeah no not quite

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I kept trying to figure out how to wire this up to get negative DC and about the best I could do was having to utilize an external ground

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Which seemed to work
For the ground i connected the positive terminal of PACO to the Ground terminal of my scope
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I slowly dialed up and adjusted it to about 5C DC

So I had -5V DC at the anode side of the diode
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And then -4.4V DC at the anode

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So I think I did this right and seems to agree with what I was looking for

Then I remembered well there's nothing wrong with the first circuit it's just that the cathode will be at zero  so I hooked it up and get about 0.67V DC at the anode

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So what's all the fuss about yeah wow the sky is blue  is this breaking news ?

The point being that earlier before this I only considered conventional current flow I just knew "the positive flowed" in the direction of the arrow

All of this kinda worked until I started trying to figure out alternating current and diodes 

What would be cool is to see some negative fluctuating DC pass through 

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The next phase was a little easier

Wanting to see negative fluctuating DC travel through a diode

I connected a diode and resistor same ones in series and added a signal to the cathode of the diode

Then put my scope probe on the anode side

When I had the DC offset of the signal at zero or above no signal passed through

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(Sorry I have no idea why my phone camera only gets a fragment of the green lines)

Now if I turn the DC offset negative the signal can be seen at the anode side of the diode

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[g1]

What makes you say "this is not negative, it is ground" ?
From the PACO schematic, the (-) terminal appears to be floating, not grounded.  So you can connect the (+) output to ground and you have a negative supply at the (-) terminal.  This seems to be what you did anyway.

[g1]

When I had the DC offset of the signal at zero or above no signal passed through

Your signal wasn't big enough.  If it had been big enough, the peaks beyond the diodes forward voltage drop would have got through and you would have seen the negative alternations of the sinewave.  This would have been rectified but unfiltered DC.

When you added the DC offset, you 'biased' the diode to be on, so the complete sinewave was able to get through.

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Yes sir thanks I will do that 

Ok I was gonna spare you the gory details but anyway

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  I need to figure out why I have a complete green 🍏 line in real life but when I take a picture I only get partial fragments