X-Y scope mode; diagonal line...

[DerStrom8]

Looking at your controls do you have Add selected in the vertical mode? If yes, turn add off and just use the X, Y mode.

Good catch Ron! I hadn't noticed that, it does look like it might be set to "add".

 

[cowboybob]

Glossywhite,

It also looks like, at first blush, that you've got your "Intensity" adjustment way too high.

A lot of beam retrace activity can be dispalyed with your intensity cranked up that high.

Course, you might have just turned it up for the photo shoot...

 

[glossywhite]

Looking at your controls do you have Add selected in the vertical mode? If yes, turn add off and just use the X, Y mode.

Also, as suggested, you will need to get a handle on Oscilloscope Basics so the scope is no longer like the controls of a space shuttle.

Ron

Hello

No, "add" is disabled; there is an LED which illuminates behind the legend, when "add" is enabled, just as with other functions

 

[Reloadron]

Wait a moment. Your post #9 with the X is showing me the signal sources going between a 0 degree phase shift and some degree of phase shift. What are the input signals doing back in your post #1? The diagonal line runs with the horizontal (X) and vertical (Y) input amplitudes. I don't think (operative word being think) it's a matter of the scope settings as much as a result of the input signals changing their phase relationships. I realize the frequencies are slightly different. I haven't a clue what Audacity tone outputs look like or how they generate left & right channel tones of different frequencies. I am just guessing what you are seeing is a function of the X,Y scope inputs and not caused by the scope. Not sure but that is my guess.

Ron

 

[DerStrom8]

Wait a moment. Your post #9 with the X is showing me the signal sources going between a 0 degree phase shift and some degree of phase shift. What are the input signals doing back in your post #1? The diagonal line runs with the horizontal (X) and vertical (Y) input amplitudes. I don't think (operative word being think) it's a matter of the scope settings as much as a result of the input signals changing their phase relationships. I realize the frequencies are slightly different. I haven't a clue what Audacity tone outputs look like or how they generate left & right channel tones of different frequencies. I am just guessing what you are seeing is a function of the X,Y scope inputs and not caused by the scope. Not sure but that is my guess.

Ron

That was the first thing I thought of, that the signals weren't perfect. I've noticed a lot of tone generators actually loop, so the tone isn't pure. I'm wondering if the transition between the end of one cycle and the start of the next is throwing things off.

I wanted to be sure I didn't miss anything in the settings.

@ The OP: Once again, I suggest getting an actual signal/function generator and see if it looks any better. If it doesn't, it's something with the scope. But my main suspicion is that you're not getting a pure tone from Audacity.

 

[Reloadron]

That was the first thing I thought of, that the signals weren't perfect. I've noticed a lot of tone generators actually loop, so the tone isn't pure. I'm wondering if the transition between the end of one cycle and the start of the next is throwing things off.

I wanted to be sure I didn't miss anything in the settings.

@ The OP: Once again, I suggest getting an actual signal/function generator and see if it looks any better. If it doesn't, it's something with the scope. But my main suspicion is that you're not getting a pure tone from Audacity.

I agree and now that you mention it those tone generators do loop I believe. Simply put, looking at the images I figure the scope is displaying what it sees or... What you see is what you got.

Ron

 

[glossywhite]

I can tell you what is feeding this 'scope:

In audacity, I have two mono tracks, one with 1000hz sine, the other with 1001hz sine. The 1000hz sine has the balance slider pulled to the left only, and the 1001hz sine has the balance slider pulled to the right (as in the picture). Could it be that there is some other in-phase noise coming through on the silent channels of each track?

Thanks

 

[DerStrom8]

I can tell you what is feeding this 'scope:

In audacity, I have two mono tracks, one with 1000hz sine, the other with 1001hz sine. The 1000hz sine has the balance slider pulled to the left only, and the 1001hz sine has the balance slider pulled to the right (as in the picture). Could it be that there is some other in-phase noise coming through on the silent channels of each track?

Thanks

As we said, tone generators make sound in loops. Chances are the transition from the end of a loop to the beginning of the next is causing some goofy signals. That and you probably do have some extra noise coming through the channels. Again, the tones are not pure. You cannot rely on them to give you a clean sine wave. If you want a clean wave, get a function generator.

There is nothing wrong with your scope, I'm 99.99% positive on that.
Matt

 

[Reloadron]

I can tell you what is feeding this 'scope:

In audacity, I have two mono tracks, one with 1000hz sine, the other with 1001hz sine. The 1000hz sine has the balance slider pulled to the left only, and the 1001hz sine has the balance slider pulled to the right (as in the picture). Could it be that there is some other in-phase noise coming through on the silent channels of each track?

Thanks

You got me curious on this Audacity thing. OK, you are using Generate and selecting Tone, then what? I know the scope is displaying what it is seeing. That said we have Generate / Tone and are you selecting a Sine or Square wave? There are other options but I assume Sine and if not try selecting Sine.

Ron

 

[glossywhite]

You got me curious on this Audacity thing. OK, you are using Generate and selecting Tone, then what? I know the scope is displaying what it is seeing. That said we have Generate / Tone and are you selecting a Sine or Square wave? There are other options but I assume Sine and if not try selecting Sine.

Ron

Yes, I'm only selecting & generating sine waves in audacity. As I always thought, I'm sure audacity isn't designed to generate 'scope test signals.

 

[DerStrom8]

I must ask, why the "disagree" on Ron's post? It was a perfectly reasonable question!

 

[glossywhite]

I must ask, why the "disagree" on Ron's post? It was a perfectly reasonable question!

Oops!

Blame Android for that - sorry Ron. My finger slipped I think.

 

[mab2]

A straight line from bottom left to top right means you have the same signal on X and Y (assuming you haven't got invert signal selected ).

I suspect the problem is much simpler - when you select X-Y mode, do you not use either CH1 or CH2 as the X input? If it uses CH1 for X then this will give you the lissajous figure for the signal on the CH2 (the oval - CH1-X CH2-Y); but if you are still operating the scope in dual trace mode then you see the second figure - the diagonal line (CH1 -X CH1-Y).

i.e. if you're using one channel for X input, you can't use it as a 2nd Y input.

 

[glossywhite]

A straight line from bottom left to top right means you have the same signal on X and Y (assuming you haven't got invert signal selected ).

I suspect the problem is much simpler - when you select X-Y mode, do you not use either CH1 or CH2 as the X input? If it uses CH1 for X then this will give you the lissajous figure for the signal on the CH2 (the oval - CH1-X CH2-Y); but if you are still operating the scope in dual trace mode then you see the second figure - the diagonal line (CH1 -X CH1-Y).

i.e. if you're using one channel for X input, you can't use it as a 2nd Y input.

This is my configuration:

With 'scope in X-Y mode...

Audacity signal LEFT channel = 'scope channel #1, "X"

Audacity signal RIGHT channel = 'scope channel #2, "Y"

 

[mab2]

OK, but it looks from your original pic as though it's still in dual trace mode - so as well as the X-Y figure you want (the oval - CH1 vs CH2), you're also getting the CH1 as a 2nd trace (the diagonal line CH1 vs CH1).

to get rid of it you need to set the 'scope to CH2 only I think.

 

[JimB]

I think that MAB2 is on the right track.

Just bare with me while I ramble a bit here.

You have selected X-Y mode by turning the SEC/DIV control fully counter clock wise.
This makes Ch1 the X input for X-Y mode.

In the MODE area of the front panel, you have buttons for Ch1 Ch2 Ch3 and Ch4.
You have both Ch1 and Ch2 selected.

Try deselecting Ch1.
I think that this will give you the Lizzy figure without the diagonal line.

I think what is happening,
by selecting X-Y mode, the scope puts Ch1 on the X axis
by having Ch1 selected in MODE, CH1 is also on the Y axis
This is why you have the unwanted vertical line.

JimB

 

[glossywhite]

I think that MAB2 is on the right track.

Just bare with me while I ramble a bit here.

You have selected X-Y mode by turning the SEC/DIV control fully counter clock wise.
This makes Ch1 the X input for X-Y mode.

In the MODE area of the front panel, you have buttons for Ch1 Ch2 Ch3 and Ch4.
You have both Ch1 and Ch2 selected.

Try deselecting Ch1.
I think that this will give you the Lizzy figure without the diagonal line.

I think what is happening,
by selecting X-Y mode, the scope puts Ch1 on the X axis
by having Ch1 selected in MODE, CH1 is also on the Y axis
This is why you have the unwanted vertical line.

JimB

Genius, I owe you a cheeseburger

The rest of you get one too, because I don't like people feeling left out ... I may buy you a rib eye steak, if you prefer

Due to the source of the 'scope, I was almost certain it is working 100%, due to the engineer who sold it to me having tested it exhaustively... I was thinking (for about 1% of my thoughts) "Oh not another fault apart from the graticule lamps being blown"

Thanks!!!

 

[JimB]

On the scale of a moldy crust of bread to full four course dinner, I think that this rates as a good bacon sandwich and a cup of tea!

Sounds like we have had some success here tonight.
I like success stories.

JimB

 

[glossywhite]

On the scale of a moldy crust of bread to full four course dinner, I think that this rates as a good bacon sandwich and a cup of tea!

Sounds like we have had some success here tonight.
I like success stories.

JimB

I knew someone here would work it out; this isn't like EEVblog forums, where you're treated like a twerp for asking a simple question, and having it continue for days (this forum is much preferred, tbh).

Well, since you are humble and only want a sandwich, you'd get WAY better from me - whatever you wanted

 

[Reloadron]

Well Amen. I duplicated things but... I was limited to a 2 channel Tek 2235 scope less the option that needed changed. I got a rotating ellipse less the diagonal line. I started thinking at that point about your settings. Came back and bingo. Thank you Jim and Mab as I was starting to lose it.

Ron