Test Equipment: Oscillocopes

[MarkE]

That's cute.

[Brian516]

Well, the Sine waves look really clean and the 90 degree oop circle is perfect. Yes, I think your sound card is probably introducing distortion for the ramp and square wave signals and the "oscillofun" FLAC file. I'm puzzled as to why you need to turn it up all the way, though. I ran "oscillofun" just at normal volume in my speakers and at the same time took the headphone output directly from the front panel headphone jack into the 10x attenuated probes and was able to see the shapes fairly cleanly, with much less distortion than your video shows.
So like I said I'm puzzled. You should be able to just use the V/div scales to set the scope at more sensitive amplification and run the sound card at normal volume, and I don't see why you can't run the speaker output and the headphone output at the same time. I'm running a seven year old Asus motherboard with onboard sound, no separate soundcard. The probes shouldn't be loading the soundcard much at all, certainly not as much as headphones would. If you run the sound card at 70 percent volume you should get much less distortion from it, and if the scope's V/div settings won't display it at that output level I'd say that there is something wrong somewhere.

I don't have to have it turned up all the way, but it helps a very little bit with the sharpness when I get above a certain volume. I can run it down to about 2% volume and still pick up the traces, especially with the sine wave (obviously with different v/div setting). It would help with the w/ or w/o HP's issue if I could eliminate that altogether and run the speakers and scope off the same audio source in sync, but the best I've managed to find for those settings is to enable both to be able to play separate signals at the same time.  (I can't get my audio player to select both the HP jack and speakers simultaneously - but can enable both so I can play two different things at the same time.)   If I were running Linux, I could probably add a setting to use both if I couldn't already. 
I'm going to try eliminating all of my splitter jacks and the 6' headphone cable I'm using and chop the cord off an old pair of HPs to about 6" long and see if it's my cables/connections that are the problem.  If that isn't it, when I get my desktop up and running, first thing I'll do is install an FG and try that.  Maybe this Samsung laptop has some built-in filter device hardware that is causing the distortion.  Whatever it is, it doesn't distort the Sine wave.

But as I mentioned before, since I do get a proper 300mv 1khz signal out of my calibrator loop on both channels, this CAN'T be a scope issue, it has to be an issue with something before the probe tips, correct?   One thing I did notice when I was playing around swapping probes is that if the grabber tip isn't fully seated on the probe tip, it tends to distort the trace. Example: when I switched back to the pp-200 probes and hooked to the cal loop, my CH2 had a flattened square wave trace. When I gave the grabber a good squeeze onto the probe, it went back to normal as soon as I got it fully seated.

Also, I had previously checked my outlet to make SURE that it is wired correctly and has ground connected, and it's all good.  However, it is the old style Anaconda 12-2 with the 12awg hot and neutral, and 14awg (or smaller) ground wire.  That is likely the reason why, if I plug a small space heater into the same source (any outlet off the same breaker) it distorts my trace.  In XY, it will take the two dots and "pull" them to the left.  That is why I intend to run at least one dedicated 20A circuit up to my workstation. If it comes down to it, I'll add a second so my scope and other similar equipment can have a dedicated line, and soldering iron, etc can hook into another. This probably has something to do with the way my house is wired. I only have a 100A box, and my ground is tied into my neutral. If I must, I'll rewire it so that I can separate the two, but that shouldn't be necessary, hopefully.
Just checked-Space heater is only two-prong, so that's not it. maybe it has to do with running a resistive load that big off the same circuit?  Just thought I'd let you know about that in case it has anything to do with any of this somehow.

[Brian516]

PNGs always seem to display, TIFs don't seem to display.  My scope puts out TIFs.

Your scope seems to be working OK.  The fuzzy signals look like a high impedance in the probe ground.  The awful square waves look possibly like an open ground connection.

Maybe the receptacle tester I used wasn't working properly, but it said that the outlets are wired correctly and grounded. Could be the extra small ground wire of the old Anaconda 12-2.  I have a new 12-2 romex lead ready to rock and roll, and will stick it up thru the hole that I drilled for it here shortly and test it that wayn. 
Another thing here is that my laptop charger is only a two-prong, so it has no designated ground lead to hook to, only the neutral.
If it's not that, or my HP wire config, and the new circuit doesn't fix it, maybe it's that the ground and neutral busses in the panelbox are bridged instead of separate?  I could fix that, I'd just have to shut down the power to the house for an hour or so.  A quick fix to that might be just running a piece of romex to a ground rod outside and connecting my outlet/box grounding to that.  Lets hope it doesn't go that far, though.   Or maybe it is the PC's integrated sound card, but I wouldn't think so since it's a fairly high end computer even being that it's a couple years old.

[just noticed someone's watching my $240 pool cue listing on ebay, hopefully they buy and that Interstate FG is still available in 5 days!!! ))))) ]

[MarkE]

In terms of keeping your equipment from doing bad things, having all the green wires connected together is important practice.  When using something with an isolated supply lie a laptop, that connection will come through the signal common, in this case the ground connection of the stereo headphone ouput.

What I was referring to was the connection between the audio common connection (internal circuit common or ground of your computer) and the oscilloscope.  This would be a problem between the audio jack and the oscilloscope Ch 1, & Ch 2 inputs.  An easy way to check is to set your oscilloscope trigger to the AC line and sweep to 5ms / div and see if the signal envelope is locked to the line.  If it is, then the signal return is being supplied through the AC mains green wire at the scope and leakage capacitance through the laptop charger.

[Brian516]

In terms of keeping your equipment from doing bad things, having all the green wires connected together is important practice.  When using something with an isolated supply lie a laptop, that connection will come through the signal common, in this case the ground connection of the stereo headphone ouput.

What I was referring to was the connection between the audio common connection (internal circuit common or ground of your computer) and the oscilloscope.  This would be a problem between the audio jack and the oscilloscope Ch 1, & Ch 2 inputs.  An easy way to check is to set your oscilloscope trigger to the AC line and sweep to 5ms / div and see if the signal envelope is locked to the line.  If it is, then the signal return is being supplied through the AC mains green wire at the scope and leakage capacitance through the laptop charger.

Made a vid to show the results of this test. From what I gather from your explanation, for some reason I do not have a ground/common connection from the laptop to scope.  Let me know your thoughts on the matter.   Also, I pointed out that there is a little dot to the left, just off screen when centered, when the scope is in standby mode. Is that normal? Watch vid and then you will understand the pic that I linked to.

https://www.youtube.com/watch?v=jkDdHDRAoyQ

http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00254_zpsxtm5ctp2.jpg