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Author Topic: Test Equipment: Oscillocopes  (Read 57368 times)

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #195 on: February 28, 2015, 06:22:48 AM »
My computer makes for the WORST FG of all time!  The only thing that actually looks the way it should from the PC is a sine wave...
Square wave looks like a cross between sawtooth and square wave... and none of the others look good at all.  I need to get my Arduino working as an FG, or maybe the Dell desktop that I picked up from storage set up and loaded with Linux and an FG since I have decent sound cards for it.  Maybe running the output thru my yamaha stereo amp would help?  I know it's not the scope, and It'd be nice to have a semi-decent FG to use until I get a real one.
I'm going to upload a few pics as soon as I get this camera/sd card issue resolved and add them to this post. They are pics of the diagonal line, circle, etc, and one or two of my horrible looking other waveforms.


After watching the Youtube video YouScope & Oscillofun and seeing what the song is supposed to look like on the scope, I realized that what I am seeing is definitely not correct. I made a vid showing what I see for most of the song. I hope it's just an issue with my PC soundcard but I somehow doubt that's the case. Whatever it is is likely the cause of my distorted waveforms (other than the sine wave).

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


Here are some test waveforms (standard and XY) off my scope and PCFG.

http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSawtooth-PCFG_zpsydiaz5rz.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSQ-PCFG_zpspmukkzwp.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSine-PCFG_zpsv7xrk0tq.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSineXY-PCFG_zps4ekkrzib.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSineXY-45OOF-PCFG_zpsuwkgcmjo.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSineXY-90OOF-PCFG_zpskllfhqko.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSquareXY-90OOF-PCFG_zpsvrcpsucv.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/10khzSquareXY-90OOF-PCFG_zpsch524ueb.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/20khzSquareXY-90OOF-PCFG_zpsq19blots.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/20khzSineXY-90OOF-PCFG_zpsp6kpnhsm.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/10khzSineXY-PCFG_zpsxqajwnrf.jpg

Time to crash. Goodnight everyone.


Just realized, it has to be a PC sound card problem, right? I mean, I get a good, clean square wave off the calibrator.... Right?? Or am I totally missing something, again?

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Re: Test Equipment: Oscillocopes
« Reply #195 on: February 28, 2015, 06:22:48 AM »

Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #196 on: February 28, 2015, 09:56:08 AM »
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.

Offline MarkE

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Re: Test Equipment: Oscillocopes
« Reply #197 on: February 28, 2015, 10:48:51 AM »
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.

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Re: Test Equipment: Oscillocopes
« Reply #197 on: February 28, 2015, 10:48:51 AM »
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Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #198 on: February 28, 2015, 11:03:06 AM »
Yep. I thought also perhaps some distortion from running the sound card all the way up. This may have been necessary due to a high impedance in the ground connection also.


I just made a video playing the two sound files into the 2213a. Direct from the headphone output, volume at about 75 percent, speakers going too (with separate VC on the speakers). 10x probe attenuation, V/div settings 500 mV/div mostly, increasing to 200 mV/div at another segment (I misspoke in the video, was reading the "1x" position on the knob by mistake, but I inserted correction titles in the vid, the 500 and 200 mV numbers are correct.)

It will take half an hour or so to process and upload the video. It is much cleaner than what Brian showed, so I think that better connections and perhaps different settings will also work to clean up his display of the files as well. (I downloaded the files and played them directly using the Ubuntu native "movie player" app rather than playing them from the YT video player on the video I linked earlier.)


One weirdness for me is that the text in the "youscope.wav" file is displaying in mirror-image or backwards or something. Nothing I've tried has corrected that. Swapping channels makes the text run vertically instead of horizontally and inverting one channel makes it upside down, but still it appears backwards instead of straight.

Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #199 on: February 28, 2015, 12:03:13 PM »
My video of the Youscope and Oscillofun audio files on the Tek 2213a is ready at:

http://www.youtube.com/watch?v=FoSPK1qRhSY

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Re: Test Equipment: Oscillocopes
« Reply #199 on: February 28, 2015, 12:03:13 PM »
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Offline MarkE

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Re: Test Equipment: Oscillocopes
« Reply #200 on: February 28, 2015, 02:16:55 PM »
That's cute.

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #201 on: February 28, 2015, 02:31:46 PM »
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.

Free Energy | searching for free energy and discussing free energy

Re: Test Equipment: Oscillocopes
« Reply #201 on: February 28, 2015, 02:31:46 PM »
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Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #202 on: February 28, 2015, 02:46:05 PM »
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!!! :)))))) ]

Offline MarkE

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Re: Test Equipment: Oscillocopes
« Reply #203 on: February 28, 2015, 04:01:19 PM »
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.


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Re: Test Equipment: Oscillocopes
« Reply #203 on: February 28, 2015, 04:01:19 PM »
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Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #204 on: February 28, 2015, 04:43:00 PM »
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

Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #205 on: February 28, 2015, 04:52:29 PM »
Yes, that little dot (or dots) off to the left, out of view offscreen when screen is properly centered but blanked from a no-trigger condition, is normal. At least both my 2213a and the HP180a do it too.

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Re: Test Equipment: Oscillocopes
« Reply #205 on: February 28, 2015, 04:52:29 PM »
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Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #206 on: February 28, 2015, 04:58:25 PM »
Ah, I think i may have figured out the problem... possibly. but it's not so easy for me to verify this....

I have tripped over my power cord/HDMI cord on multiple occasions and damaged the charger port of my computer... and it is now to the point where it rarely actually charges the battery when plugged in.  The computer will run off the AC source, but I have to squeeze around the port and play with it a bit to get it to charge, and it's become really hard to get it to actually charge.   Upon closer inspection, I see that there are in fact two contact points to the outer ring (neutral/ground connector) of the plug, and one, being most likely the ground from the laptop, must have a broken connection from the motherboard.  If I am correct and that is the case, then I have found my reason why I am not getting a solid ground connection between the laptop PSU and the scope.

At some point I will have to take my laptop apart to access the PCB where the port is attached and fix it. I just ordered an original replacement off ebay for $4, so when I get it and replace it I will try again with my laptop and see if that was the issue.  I'm not going to bother trying to fix the one that's in it, so I only have to take it apart once.... going to have to grind down a soldering iron tip to a superfine point for this task. I broke a 30W soldering iron the other day (heater wire broke free from contact) and am going to mod it and make it a 15 or 20W. which would you suggest I go with? my 6-8W is battery op and kinda sucks, and next one up from that is 25W. Also, should I spread out the heater wire, keep it all at the back, or all at the front?  _sorry for the off-topic question_!!)

Offline MarkE

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Re: Test Equipment: Oscillocopes
« Reply #207 on: February 28, 2015, 05:14:29 PM »
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
It looks like the common is open between the headphone out and the oscilloscope input.

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #208 on: February 28, 2015, 05:38:41 PM »
It looks like the common is open between the headphone out and the oscilloscope input.

If what you're saying means that the whole laptop to AC source ground connection being broken doesn't matter, and what matters is the soundcard ground to scope ground, I'm not sure what the problem is.  I checked continuity in the probe's grounds, and they're good, and checked continuity in my headphone cable setup, and they're all good.  So what you are telling me is that either the PCB ground to HP jack ground is broken/not connected, or my scope input connector to machine internal ground is broken?

I checked the continuity between the collars of the BNC and the ground input plug on the face of the scope, and it's good. It's also good from the scope plug ground prong to the BNC collars and the ground connection plug on the face of the scope. So it's back to the PC, correct?

I'm so sick of having problems with stuff!!!! I just want it all to WORK so I can LEARN HOW TO USE IT ALL!!! AHHHHHH

Offline MarkE

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Re: Test Equipment: Oscillocopes
« Reply #209 on: February 28, 2015, 07:32:48 PM »
If what you're saying means that the whole laptop to AC source ground connection being broken doesn't matter, and what matters is the soundcard ground to scope ground, I'm not sure what the problem is.  I checked continuity in the probe's grounds, and they're good, and checked continuity in my headphone cable setup, and they're all good.  So what you are telling me is that either the PCB ground to HP jack ground is broken/not connected, or my scope input connector to machine internal ground is broken?

I checked the continuity between the collars of the BNC and the ground input plug on the face of the scope, and it's good. It's also good from the scope plug ground prong to the BNC collars and the ground connection plug on the face of the scope. So it's back to the PC, correct?

I'm so sick of having problems with stuff!!!! I just want it all to WORK so I can LEARN HOW TO USE IT ALL!!! AHHHHHH
There is a simple test:  Hook your laptop to an AC powered stereo.  If you get a bunch of 60 cycle hum then you have a bad ground connection.  If not, then there is something else going on with your oscilloscope set-up.

 

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