Can you figure this out... - Page 1
Forum section: electronics / general

author: Matty
author_rank: Contributor
timestamp: November 12, 2016, 09:05:19 pm
content: Just for a laugh. Can you guess what signals are going into the scope...https://youtu.be/TPWfcFm9oi4

author: ZeTeX
author_rank: Frequent Contributor
timestamp: November 12, 2016, 09:42:43 pm
content: Whatever it is, do it with a digital scope, I dare ya.

author: ataradov
author_rank: Super Contributor
timestamp: November 12, 2016, 10:55:01 pm
content: X is sine wave, Y is a modulated sine wave?Quote from: ZeTeX on November 12, 2016, 09:42:43 pmWhat problems do you see doing this with a digital scope?

author: ZeTeX
author_rank: Frequent Contributor
timestamp: November 12, 2016, 11:01:38 pm
content: Quote from: ataradov on November 12, 2016, 10:55:01 pmThat most of the digital scopes will not show the wave form so smooth and sharp. I would like like to see it on a digital scope actually to see how good and smooth the wave form.

author: ataradov
author_rank: Super Contributor
timestamp: November 12, 2016, 11:08:18 pm
content: Quote from: ZeTeX on November 12, 2016, 11:01:38 pmI'm far tool lazy to replicate this myself, bu here is a video of Tek doing a reasonable job displaying things and doing some measurements at the same time:

author: Matty
author_rank: Contributor
timestamp: November 12, 2016, 11:36:15 pm
content: Quote from: ZeTeX on November 12, 2016, 09:42:43 pmMakes no difference. You can still see the 'ripple'.Quote from: ataradov on November 12, 2016, 10:55:01 pmThats 70% right. There is another 30% to go.

author: Brumby
author_rank: Unknown
timestamp: November 12, 2016, 11:52:17 pm
content: Are you after frequency and amplitude relationships...?

author: Delta
author_rank: Super Contributor
timestamp: November 12, 2016, 11:57:44 pm
content: X-Y mode, sine waves with a 1 Hz difference?

author: Brumby
author_rank: Unknown
timestamp: November 13, 2016, 12:09:14 am
content: Just eyeballing .....X axis:Sine wave of frequencyf; amplitude according to X axis amplifier gainY axis:Sine wave of frequency 3f; amplitude 100% **Sine wave of frequency 3f+/- 1 ; amplitude ~60% **Sine wave of frequency something like 50-60f; amplitude ~5% (the ripple)Z axis:No discernable AC input** There is also a slight frequency variation of the 3ffigure of something just under 2Hz

author: Matty
author_rank: Contributor
timestamp: November 13, 2016, 02:46:28 am
content: wow Brumby, that's a hell of answer. But that's not quite it. I was expecting a more simple answerANSWER (highlight to see):Quick Answer:X and Y both have a sine waves of different frequencies.Y also has Amplitude Modulation added on.X also has Frequency Modulation added on.Longer Answer:As this is a Lissajous curve, X and Y have a ratio of ~3:1, you can see there 3 'curves' on the X axis.The Y Amplitude Modulation is very small about 1Hz, to see the bouncing.The X Frequency Modulation is much higher about 10Khz in this case.In a previous post I typed 'ripple' in quote marks, which I guess was misleading

author: Brumby
author_rank: Unknown
timestamp: November 13, 2016, 03:08:09 am
content: OK - Yes, it's a Lissajous figure. Didn't think to include the obvious.Approximate frequency ratio determined by the number of points of contact on two adjacent sides of a rectangular box containing the figure. Actual frequency ratio will include the speed of 'shift'.My first sighting of such was in the logo for the ABC (Australian Broadcasting Commission) television station (VHF Channel 2 in Sydney, in the day.)A little bit more stylised these days:

author: jonovid
author_rank: Super Contributor
timestamp: November 13, 2016, 03:14:24 am
content: Quoteyes something from the Australian Broadcasting Corporationif you want the politics.its in the datasheet

author: Brumby
author_rank: Unknown
timestamp: November 13, 2016, 03:23:40 am
content: I speak of it's incarnation at the time of my first encounter.It became the Australian BroadcastingCorporationsome time later ... 1983 I believe.And, yes, it did have it's fair share of issues with those running the place wanting to maintain objectivity up against the political forces that were in play.

author: Brumby
author_rank: Unknown
timestamp: November 13, 2016, 03:24:49 am
content: ... but stuff the politics - I just wanted to make a Lissajous figure of my own.

author: calexanian
author_rank: Super Contributor
timestamp: November 13, 2016, 05:21:00 am
content: We had too make that waveform in the modulation section of intro to electronic communications class. It was said before. X axis sine wave with some ripple or something on it, and y axis sine wave modulated at either a low frequency, or a roll and tumble if its up higher in frequency. Cant tell cause I can't see the scope settings. I made it with four XR2206 circuits because we also had to modulate the X axis too.

author: Brumby
author_rank: Unknown
timestamp: November 13, 2016, 12:37:33 pm
content: This example has a sine wave on the X axis - but the ripple is on the Y axis.

author: ZeTeX
author_rank: Frequent Contributor
timestamp: November 13, 2016, 05:27:45 pm
content: Quote from: ataradov on November 12, 2016, 11:08:18 pmOn a 11k$ scope, sure, I meant "cheap" digital scopes..

author: tom66
author_rank: Super Contributor
timestamp: November 13, 2016, 06:19:17 pm
content: Quote from: ZeTeX on November 13, 2016, 05:27:45 pmMy Rigol DS1054Z actually does a reasonable job of YouScope, which is of a similar order. It has no issue at all displaying Lissajous figures.

author: ZeTeX
author_rank: Frequent Contributor
timestamp: November 13, 2016, 08:28:34 pm
content: Quote from: tom66 on November 13, 2016, 06:19:17 pmWho knew, I taught most of the cheap digital scopes will struggle with stuff like that.

author: ataradov
author_rank: Super Contributor
timestamp: November 13, 2016, 09:20:20 pm
content: Quote from: ZeTeX on November 13, 2016, 08:28:34 pmHere is a video of a Rigol DS1054Z doing similar thing:And here is some coll art that would be impossible on an analog scope (without fast beam blanking):