Caught in an oscilloscope trap for young players. - Page 1
Forum section: electronics / beginners

author: jsi
author_rank: Regular Contributor
timestamp: May 28, 2016, 05:24:07 pm
content: After the longest week in history waiting for my new Rigol DS1054Z to arrive it finally came! I spent every spare moment while waiting watching youtube oscilloscope tutorials. And, now that it's here every moment has been spent working with it.However, I have been beating my headwith what seems like a simple adjustment. My project involves an analog phone circuit. When I connect the probes to the Tip and Ring there is +48 volts between them. Riding on top of that 48V (if that's the correct terminology) is the signal that I'm interested in. It's roughly a 2V sign wave. When I adjust the vertical scale to anything less than 5V the trace is off the top of the screen. The vertical position adjustment goes to -20V and then beeps about the parameter being limited. I've been through the user manual and the only thing I've found that talks about vertical position is the "VerticalRef." setting under Utility, System. I've tried the ground and center options without luck.So, is there a way to see that sign wave at a greater resolution? There's something in there that's causing a problem and I'd like to see it.

author: drtaylor
author_rank: Regular Contributor
timestamp: May 28, 2016, 05:28:18 pm
content: Use AC Coupling, not DC Coupling on your input to reject the DC Component.

author: Kalvin
author_rank: Super Contributor
timestamp: May 28, 2016, 05:32:35 pm
content: Typically the digital oscilloscopes have possibility to perform some arithmetics between the channels, if the AC coupling is not a viable solution.

author: jsi
author_rank: Regular Contributor
timestamp: May 28, 2016, 05:40:51 pm
content: Quote from: drtaylor on May 28, 2016, 05:28:18 pmAre you kidding me? That's it! I won't say how long I spent down that rat hole.Thanks

author: w2aew
author_rank: Super Contributor
timestamp: May 28, 2016, 06:13:06 pm
content: Quote from: jsi on May 28, 2016, 05:40:51 pmAC coupling is the most commonly used mode for this type of thing. Also, many digital scopes have a Vertical Offset control in addition to the Vertical Position control. The Offset lets you dial in a DC offset (from ground) to make it possible to view a small varying signal on top of a large DC voltage. This latter method preserves the ability to make absolute voltage measurements.

author: DimitriP
author_rank: Super Contributor
timestamp: May 28, 2016, 06:15:27 pm
content: That's what happens when you don't know what all the buttons do.

author: bitseeker
author_rank: Super Contributor
timestamp: May 29, 2016, 05:29:54 am
content: A lot ofand a littlejust indicates that you're really learning the ropes. Keep up the good work and have fun with your new scope.

author: Ian.M
author_rank: Super Contributor
timestamp: May 29, 2016, 06:11:31 am
content: Its not so much a matter of knowing what the buttons do, its that their functions change according to what mode the scope's in and what other selections are active.That's why its a pity that its no longer economically viable for novices to learn on a real CRT pure analog scope. You wouldn't be confused for long by input coupling if it was a physical three position lever switch AC-Gnd-DC right next to the input BNC, and if you were used to having to ground the input and tweak the Y shift to zero the trace to whichever graticule line was convenient for the waveform you were viewing. You'd also probably get to meet the joys of 'Pull x10' on the Y variable gain knob which would sum in an AC coupled x9 amplified signal to give a DC gain of x1 and an AC gain of x10, letting you look at noise/ripple on power rails or other slowly varying or DC signals without them shooting off the screen.However a new analog scope with reasonable performance costs the same or more than an entry level digital scope, and I wouldn't wish an chronically unreliable crusty old boatanchor on an absolute novice, even at under $50.My first scope was all valve: Hartley Electromotive Type 13A Oscilloscope, just like this one, except mine was less beat up and had its original CRT hood and a graticule.It was a reliable dual beam boatanchor, but had rather limited bandwidth and a piss poor trigger. It taught me a lot and I even used it for figuring out serial keyboard protocols and the like.

author: tggzzz
author_rank: Super Contributor
timestamp: May 29, 2016, 07:27:45 am
content: Quote from: jsi on May 28, 2016, 05:40:51 pmWe've all "been there, done that".With any new piece of equipment it is highly beneficial to understandhowit works internally at a block-diagram level. A good way to approach that is to learnwhyevery control is there.That takes time, and is made more difficult by not only by more complex equipment, but also by equipment with "hidden" controls. In that respect old analogue equipment is better for beginners, since all the controls are visible on the front panel.

author: DimitriP
author_rank: Super Contributor
timestamp: May 29, 2016, 08:20:57 am
content: Quote from: DimitriP on May 28, 2016, 06:15:27 pm...and then there are those pesky on-screen indicators ....

author: Gyro
author_rank: Super Contributor
timestamp: May 29, 2016, 09:23:46 am
content: (Sorry, couldn't resist)

author: JPortici
author_rank: Super Contributor
timestamp: May 29, 2016, 09:47:45 am
content: It's more a matter of reading the manual if you have no idea on how something works

author: tggzzz
author_rank: Super Contributor
timestamp: May 29, 2016, 10:04:55 am
content: Quote from: JPortici on May 29, 2016, 09:47:45 amThe quality of manuals isveryvariable.Some manuals, typically from older expensive equipment, are good at teaching you the fundamentals of how the instrument work, and how to use it. Great for beginners.Some describe where functions are, but don't tell you why they are there nor when you should use them. OK if you already know how to use similar instruments, not much use for beginners.Some manuals not much more than listings of menu items, possibly in poor English. Useless for experts and little use for beginners.

author: JPortici
author_rank: Super Contributor
timestamp: May 29, 2016, 10:41:24 am
content: well in this case the mso&dso1000z user guide (not the quick user guide that comes printed with the scope) is quite readable, though explaining things using layman's terms (yes, it is poor english after all)http://beyondmeasure.rigoltech.com/acton/attachment/1579/f-050a/1/-/-/-/-/MSO1000Z%26DS1000Z_UserGuide.pdfit's not a HP/Tektronix manual from the 70's but i have to say it's better than most manuals i've encountered in recent years(in this example.. it blocks the dc component. not technical but the first time user could say to himself "uuuuh i'm only interested in the ac over the 48V dc so i should use this one")