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Author Topic: Test Equipment: Oscillocopes  (Read 58267 times)

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #165 on: February 26, 2015, 05:42:24 AM »
Well it appears that this was a software issue of some kind. 
I am currently running the "Wave Gen" feature from Visual Analyzer and I am able to detect the PROPER signals perfectly fine.

I will do some more PC FG/Scope testing tomorrow, and possibly make another vid of the performance of the PC FG's that I have and all that.

So, Bill, yes, we can in fact hook directly in to the 3.5mm's output with the scope and measure the traces. It is as easy as that! :) 
Well, as long as you use the correct playback software and disable all of the "enhancement" features on the PC.  If you would like, I will try and figure out what playback software works best for sending directly out to the scope for viewing. So far, Visual Analyzer seems to work pretty good as a FG, and has many other tools to immerse yourself in.  Seems to be a good program to have in addition to the Soundcard Scope. That prog's FG doesn't seem to be of any use to me, but the Scope part's trace seems to be close to the trace on the Tek 465. However, it is still running on internal loopback, so I won't know exactly how good of a PC scope it is until I make a BNC to 3.5 connector at some point, which will be easy.

Brian

Brian

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Re: Test Equipment: Oscillocopes
« Reply #165 on: February 26, 2015, 05:42:24 AM »

Offline picowatt

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Re: Test Equipment: Oscillocopes
« Reply #166 on: February 26, 2015, 05:46:21 AM »
There must be an issue with using my computer to put a signal to the scope....
For some reason, the 465 displays the exact same trace no matter what signal I output from my PC. This is the case whether I connect the probe to Left, Right, or Ground. The sounds change in the headphones I wired in, and on proper channels and all that.
If I hook up the 'ground' to the ground out of the PC, it cancels out the signal.

If you cannot connect the scope ground to the HP jack ground (sleeve connection) without killing the AUDIO signal to the HP jack, then you can go no further until you figure out why.  Without the scope's signal ground connected to the laptop's signal ground, you will see all manner of AC noise when connecting a probe/scope input.

I have three different models of laptops here and I do not have any similar issues as what you describe.  I can, using adapters, plug my laptop HP output directly into a stereo receiver's line inputs or into a scope's inputs without any problem.

Some HP/speaker amplifier IC's use circuity to detect when a HP is plugged in, and I believe I have seen one that floats the sleeve to a DC potential to eliminate cap coupling the HP output.  Possibly connecting the scope ground may be messing with that HP detect circuitry.  But again, I have never had a similar issue with my laptops.

If your laptop has a third prong on its AC cord, use your DVM set to low ohms and measure between the HP jack sleeve and the third prong (ground) on the laptop AC cord.  Report back what you measure.

Also, check for continuity between the scope's ground and its AC cord third prong (I am assuming it is not cut off and that the laptop and scope were plugged into the same AC duplex/power strip).

Try running the laptop only on its internal battery (unplug the charger) and see iif you can connect the scope ground to the HP jack sleeve without muting the sound in the headphones.  Also make certain the cord you made up is wired correctly.

Quote

What I see when I hook it to the PC out is a crappy looking sine wave trace at 150V.


If you cannot connect your scope ground to your HP jack ground, this "crappy sine wave" is what you will see. 

Quote

I tried various different settings - AC and DC coupling show the same trace.
Trigger level does nothing.
Anything but "A" on Horizontal Display makes it extremely bright except for the first half of the sine wave.

I didn't bother switching to one of my Tek probes to see if the sine wave trace looked any better. seems pointless to do.

I also disabled all audio enhancements and DC offset cancellation, etc. It should be 'direct output'.
About to make a quick video to show what I am talking about, then I'm going to figure out how to use the GR Oscillator and see what that looks like on the scope.
https://www.youtube.com/watch?v=E9l-EnME9Vw

Brian


Offline picowatt

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Re: Test Equipment: Oscillocopes
« Reply #167 on: February 26, 2015, 05:55:08 AM »
Well it appears that this was a software issue of some kind. 
I am currently running the "Wave Gen" feature from Visual Analyzer and I am able to detect the PROPER signals perfectly fine.

It seems to have something to do with sending the signal directly to output.  I have to have the "send direct" box checked in the Wave Gen in order to get the proper trace on my scope.

I will do some more PC FG/Scope testing tomorrow, and possibly make another vid of the performance of the PC FG's that I have and all that.

So, Bill, yes, we can in fact hook directly in to the 3.5mm's output with the scope and measure the traces. It is as easy as that! :) 
Well, as long as you use the correct playback software and disable all of the "enhancement" features on the PC.  If you would like, I will try and figure out what playback software works best for sending directly out to the scope for viewing. So far, Visual Analyzer seems to work pretty good as a FG, and has many other tools to immerse yourself in.  Seems to be a good program to have in addition to the Soundcard Scope. That prog's FG doesn't seem to be of any use to me, but the Scope part's trace actually matches my Tek 465 nearly exactly, so it must be fairly decent.

Brian

Brian

Brian,

Have you tried just playing some music on the laptop while looking at it with the scope?

Keep in mind that the AC levels at the HP jack will be fairly low level with the HP's connected.

PW

Free Energy | searching for free energy and discussing free energy

Re: Test Equipment: Oscillocopes
« Reply #167 on: February 26, 2015, 05:55:08 AM »
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Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #168 on: February 26, 2015, 06:07:45 AM »
Yes, that signal is not coming from the PC's audio output, it's more like a distorted 60 hz hum. I can't see the horizontal scale so I can't tell the frequency of the display on the scope.

But it seems that you now have the issue sorted, by using different software and making some different output settings on the PC.

Selecting other Horiz Display modes than "A" "lock knobs" gets into the delayed timebase features of the scope and we aren't ready to go there yet.

For fun audio display of music try the X-Y setting on the Time/div knob with CH1 connected to the L and CH2 connected to the R speaker outputs. This will give you a complex "Lissajous" pattern instead of a horizontal sweep.

Jerobeam Fenderson:
http://www.youtube.com/watch?v=l8m5L2gqHPw

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #169 on: February 26, 2015, 06:11:18 AM »
Quote
Brian,

Have you tried just playing some music on the laptop while looking at it with the scope?

Keep in mind that the AC levels at the HP jack will be fairly low level with the HP's connected.

PW
PW,

I've edited my last post a little since you last read it.   
I don't know what exactly the issue was, but for some reason it seemed to be a software issue with that Soundcard Scope program, since VA's FG is running fine, and I have the reference clip (ground clip) hooked to the 'ground' sleeve of the 3.5mm (well, the wire I ran off of a jack).
I wanted to test it with some simple FG waveforms first. That way I know what I am supposed to see, and know if the scope shows the correct trace or not.
Now that I have it working, and am seeing the correct traces, I will run some music into it while listening tomorrow, and play around some more with the PC FG's I have.  Maybe I'll even figure out what was causing the issues with using Soundcard Scope.

I did notice that the trace drops about 2/3 amplitude when I plug the HPs in. With the output volume at 15% I'm reading about 225mV w/o HPs, and about 80mV with HPs.

Brian

Free Energy | searching for free energy and discussing free energy

Re: Test Equipment: Oscillocopes
« Reply #169 on: February 26, 2015, 06:11:18 AM »
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Offline picowatt

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Re: Test Equipment: Oscillocopes
« Reply #170 on: February 26, 2015, 06:17:12 AM »
PW,

I've edited my last post a little since you last read it.   
I don't know what exactly the issue was, but for some reason it seemed to be a software issue with that Soundcard Scope program, since VA's FG is running fine, and I have the reference clip (ground clip) hooked to the 'ground' sleeve of the 3.5mm (well, the wire I ran off of a jack).
I wanted to test it with some simple FG waveforms first. That way I know what I am supposed to see, and know if the scope shows the correct trace or not.
Now that I have it working, and am seeing the correct traces, I will run some music into it while listening tomorrow, and play around some more with the PC FG's I have.  Maybe I'll even figure out what was causing the issues with using Soundcard Scope.

I did notice that the trace drops about 2/3 amplitude when I plug the HPs in. With the output volume at 15% I'm reading about 225mV w/o HPs, and about 80mV with HPs.

Brian

Brian,

Glad your getting it sorted out.  The levels you are measuring sound about right, including the noted level drop when the HP's are connected.

Connect the L&R output to the scope channels 1&2.

Grab a tune off of youtube and play some music...

Don't forget to play with the X-Y mode as TK suggested at some point as well.

PW

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #171 on: February 27, 2015, 01:04:13 AM »
Greetings everyone,

I'm back at it with this scope today finally, and I'm running into some new issues.
I'm going to make a video to show as much as I can here in a few minutes, but I am first going to give a brief description of the issues.
It seems to have to do with the triggering for the most part.

After having it powered on for around 15 or 20 minutes, the trace started to get fairly unstable. It would 'jitter' around a lot, and had a horizontal line which seemed to 'start' from the right side and 'pull' the trace at the peripheral of the line. (I had two channels in, one top one bottom, line occurring on both traces).

At first, in order to get a stable trace on a different time/div setting from .5ms, I had to change from ALT to CHOP and put the trigger coupling to HF REJECT on both channels. It did this in both AUTO and NORMAL trigger modes.

-Among other issues that it is having which I will do my best to show in the video I'm about to make.

Brian

I don't know what kind of issues I may be having with my PC output again, but I went back to step 1 and hooked both channels to the calibrator loop on the scope and everything seems to be OK.
However:

In order to get a stable trace outside of the .5ms setting, I had to switch 'A trig coupling' to "HF Reject".. my settings are as follows:
[Input side]  X10 probes; 20m/div; DC input coupling; CHOP
[Trigger side] Mode: AUTO; Source: NORM; Levels=0; Slope +; holdoff: Normal; Horiz: A.

If you are going to see what all this is looking like on your scope, put it on AC or DC trigger coupling (doesn't matter which on mine) and start at .5ms. Switch out of .5ms and see if you have to put it in HF Reject mode to get a stable trace.
On the ALT vertical setting, I have to have the trigger coupling on LF Reject for anything outside of .5ms, and DC trigger coupling on .5ms.

Ok, now there are some seriously weird things happening with this scope and the settings. Actual scope issues video time...

Free Energy | searching for free energy and discussing free energy

Re: Test Equipment: Oscillocopes
« Reply #171 on: February 27, 2015, 01:04:13 AM »
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Offline Brian516

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Offline MileHigh

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Re: Test Equipment: Oscillocopes
« Reply #173 on: February 27, 2015, 03:04:42 AM »
Brian:

It looks like there is nothing wrong with your scope.  The beam is disappearing when you are not triggered.  I suggest that you watch most of the clips from this link:

https://www.youtube.com/user/AllAmericanFiveRadio/search?query=oscilloscope

You have to adjust the trigger level to get a stable waveform.  It's the most important adjustment for getting a stable waveform.

There is nothing to clean in your scope.  Over the next week or two you need to learn how to use your scope, then perhaps consider working on it.  However, it looks like the scope is fine and there is nothing for you to do to it.

MileHigh

Free Energy | searching for free energy and discussing free energy

Re: Test Equipment: Oscillocopes
« Reply #173 on: February 27, 2015, 03:04:42 AM »
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Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #174 on: February 27, 2015, 03:45:33 AM »
When I was attempting to clean up the waveform/stabilize it and would change the trigger Level adjustment, nothing at all would happen.
I will try again, though. Just to be positive.

I will watch the vids on that page that have to do with the O-scope, plus some others look pretty interesting also.

This is obviously after I learn how to use my equipment, but I was thinking a great place to start experimenting might be with tank circuits and crystal radios, and that channel fits right in there.

Brian

Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #175 on: February 27, 2015, 04:02:00 AM »
Yes, Brian, when the trigger mode is not in "AUTO" the scope's display blanks and shows nothing when the waveform is below the trigger level. This is done to save the phosphor. Like if you aren't actually using the scope but you have it on to keep it warm, there is no point in having a straight line burning the phosphor, so the scope blanks the display in the Normal trigger modes. This is not a problem.  I usually use "Auto" to set baselines and to look at very small signals, then switch to Normal so that the display blanks when not actually viewing a signal or the signal is below the set Trigger Level.

You adjust the trigger Holdoff a lot during the video and I kept wanting you to adjust the Trigger Level instead. Also you need to make sure the trigger Source is on the channel you want to trigger on! If you are triggering on CH1 and you turn that channel off by selecting Ground on the input coupling switch, the scope can't trigger!  I can't see the scope's controls clearly enough in the video to see what's going on but it seems to me that the thing is behaving fairly normally as far as I can see.

It may be that there is some extra noise coming in that is causing it to be unstable unless HF or LF filtering is on. You are changing so many things and I can't see the critical settings well enough to diagnose this problem. It may be that the Holdoff control doesn't need to be perfectly on the "normal" line  to get a stable trigger; this may be a calibration issue or a result of the noise on the signal.

Instead of using "Chop" please use "Alt" on the Vert Mode, connect both probes to the Calibrator, then select either CH1 or CH2 on the Trigger Source instead of "Norm". Then use the Trigger Level control to try to get a stable display. Check the difference between Auto and Norm trigger Modes as you vary the V/div setting on the channel you are triggering on. In Norm Mode the screen will go blank when the trigger level is set out of the range of the signal amplitude. This will also depend somewhat on the vertical position of the trace, you can take the trace out of the trigger level by moving it up or down on the screen and if you are in Norm Mode the screen will blank when you do that. This is what you were seeing in part of the video where the traces would disappear as you moved them up or down with the Vert Position control.

Free Energy | searching for free energy and discussing free energy

Re: Test Equipment: Oscillocopes
« Reply #175 on: February 27, 2015, 04:02:00 AM »
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Offline Pirate88179

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Re: Test Equipment: Oscillocopes
« Reply #176 on: February 27, 2015, 04:13:28 AM »
Yes, the AllAmericanFive radio guy is fantastic and knows what he is talking about.  I find his videos fascinating and very educational.  He actually did a video and mentioned my Tripplett meter as he has one as well.  He came up with the battery hack that I use because they no longer make those old 30 volt batteries.  Great guy.

Geeze, after watching that guy, and Dave at EEvlog, and listening to TK, MH and Mark...you would think that I would have learned a lot more than I have by now.  Some of the info sinks in, and some of it goes right through and I have to learn it again..ha ha.

But seriously, check out that guy's videos Brian...they are indeed great.

Bill

Offline Pirate88179

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Re: Test Equipment: Oscillocopes
« Reply #177 on: February 27, 2015, 04:13:43 AM »
Yes, the AllAmericanFive radio guy is fantastic and knows what he is talking about.  I find his videos fascinating and very educational.  He actually did a video and mentioned my Tripplett meter as he has one as well.  He came up with the battery hack that I use because they no longer make those old 30 volt batteries.  Great guy.

Geeze, after watching that guy, and Dave at EEvlog, and listening to TK, MH and Mark...you would think that I would have learned a lot more than I have by now.  Some of the info sinks in, and some of it goes right through and I have to learn it again..ha ha.

But seriously, check out that guy's videos Brian...they are indeed great.

Bill

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #178 on: February 27, 2015, 05:08:41 AM »
Ah, now I feel stupid.

I should have thought a little bit more about what exactly the different settings do and what they change.
Also, for some reason I was thinking that when part of the trace was going off-screen it wasn't affecting anything, that it was just simply going out of the viewing range.  Now I know that's not the case.

As for the trigger level adjustment, I must have been thinking that it was as sensitive as most of the other controls. So far, now that I know WHEN to use it, it is the least sensitive control of all of them. Scratch that, it can be very touchy at times also. Starting to get the hang of things now..

I will be watching a lot more instructional videos in the coming days so I can not only avoid feeling stupid, but stop bugging everyone with stupid questions and false problems!! That AllAmericanFiveRadio channel is definitely a good place to start.



Brian

Offline picowatt

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Re: Test Equipment: Oscillocopes
« Reply #179 on: February 27, 2015, 05:42:46 AM »
Brian,

Here is a real quick and simple explanation of what the trigger and trigger level do.

Let's say you have the horizontal sweep set to 1ms per division.  The trace effectively sits and waits off screen on the left side of the display until the scope receives a trigger pulse, which, like a starting pistol at a race, makes the trace race across the screen toward the right at the horizontal rate you selected (the 1ms per division).  Once the trace gets over to the far right side of the screen, the trace is temporarily shut off (blanked) and at very high speed races back over to the left side and again just sits there and waits for a trigger pulse.  And so on and so on...  No trigger, no racing off to the right.

Now, let's say you have a sine wave input to channel 1 that goes from +1 volt to -1 volt.  The trigger level is used to determine at what voltage a trigger pulse is generated.  Note that your trigger level control is labeled as positive or negative, with zero being straight up.  If you adjust the trigger level for +0.5 volts, when the incoming sine wave exceeds +0.5 volts, the scope generates a triggerpulse and sends the trace off and running across the screen.  When the trace returns to the left side, it will again sit and wait, but only until the incoming sine wave again exceeds +0.5 volts, which produces another trigger pulse and again sets the trace off toward the right.  This causes the trace to scan across the screen, overlaying a new image of the sine wave over the still fading out previous sine wave image.  The images overlap perfectly because the trace is always starting out from the left side at the same point in the cycle of the sine wave (the point where the sine wave reaches the +0.5 volts that the trigger is set to).

Now, if you turn down the level of the sine wave being fed to the scope so that it only goes from +300mv to -300mv, and you don't readjust the trigger level, which is still set at +0.5 volts, the scope will never generate a trigger pulse because the incoming signal never exceeds the +0.5 volts that the trigger level is set to.  This is why the trigger level control is important and needs to be adjusted for the most stable display of every waveform you display.

Stable repetitive waveforms such as those coming from a function generator or the calibrator are fairly easy to get a solid trigger from and produce stable displays that exactly overwrite the previous scan.  Complex waveforms, such as music, are a bit more difficult to trigger on, but using the HF reject and attempting to set the trigger level so that the trigger is generated from the typically larger low frequencies (bass notes) will produce a usable display, particularly at lower sweep speeds.

Turn your trigger holdoff knob to "normal" (which is minimum holdoff) for now and just leave it there!!  You won't be needing any holdoff for repetitive signals (FG, calibrator, etc)

PW   

 

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