Film-Tech Forum ARCHIVE: Portable Osciloscope

This is topic Portable Osciloscope in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Fernando Cavallero (Member # 4241) on 07-30-2008, 10:12 PM:

Hello,
I´ve been using my old CRT scope for many years. It has a 2 by 2 inches screen and is very light and portable.
I´m thinking to upgrade to a digital one.
Which are the best options to work in the field?
The azimuth in some digital scopes is terrible (many dots without a shape)
I don´t know if should buy a "USB scope" to use with a notebook or a handheld style...
Thanks!

Posted by Robert Minichino (Member # 3495) on 07-30-2008, 11:08 PM:

I'm not so sure a digital oscilloscope is an 'upgrade' from an analog CRT scope. I have both and I still find myself going back to the CRT scope for certain tasks. I've heard good things about Tek's Digital Phosphor scopes, but they're a bit out of my price range.

Posted by Gordon McLeod (Member # 33) on 07-30-2008, 11:23 PM:

I have yet to see a pc based scope that works like a CRT scope for a digital alignement
I still use my old leader

Posted by Mark Gulbrandsen (Member # 72) on 07-31-2008, 06:55 PM:

The more expensive Tektronix and I'm sure other high end digital scopes work well with all the waveforms we typically view. Big bucks though! PC based scopes just don't cut the mustard... or was that wind???

Mark

Posted by Louis Bornwasser (Member # 3063) on 07-31-2008, 08:29 PM:

Both Fluke & Tek sales angineers tried to properly display the Dolby Digital waveform and struck out (badly). I would e-bay a 1970's Tek for 150-200 bucks. Louis

Posted by Fernando Cavallero (Member # 4241) on 07-31-2008, 09:47 PM:

I agree with Robert that digital is not an upgrade. But the dammed "modern technologies" are pushing us to the digital domain.

Can you believed that mi CRT is 30KHZ bandwith! and you can see the video sygnal perfectly.

Posted by Scott Norwood (Member # 30) on 07-31-2008, 11:21 PM:

Out of curiousity, what does a digital oscilloscope do that an analog scope dosn't? (I've only ever used analog CRT models.)

Posted by Robert Minichino (Member # 3495) on 07-31-2008, 11:49 PM:

All sorts of cool stuff, like displaying the waveform before the trigger event, fancier triggering modes, fancy math on waveforms, FFT spectrum analysis. Plus they cost more and only the hugely expensive ones are intuitive for analyzing signals with transients.

Posted by John Hawkinson (Member # 1135) on 08-01-2008, 05:42 AM:

I think the biggest feature of a digital oscilloscope is having a useful one-shot trigger with persistent display. So you can watch a non-periodic event from the moment it happens, and not have to worry about only having a split-second to see it before the phosphors disappear. (Yes, there are specialized analog scopes that solve this problem, too, but they're not exactly commonplace.)

Another handy feature is that you can download the trace to a computer, either so you can extract precise data from the trace, or so you can have a handy screenshot without the added aggravation of a camera.

They also seem to have less useful user interfaces, with many more buttons that are modal and overloaded with multiple functions [Frown]

--jhawk

Posted by Louis Bornwasser (Member # 3063) on 08-01-2008, 05:49 AM:

The up side is that they are very good at showing the outside of a waveform; very bad at the "grass" inside it. Too bad, but that is required for DD set up. Louis

Posted by Scott Norwood (Member # 30) on 08-01-2008, 09:21 AM:

So, essentially, a digital scope doesn't really offer much, if any, benefit for typical cinema use (sound alignments), correct?

Posted by Andres Briano (Member # 4621) on 08-01-2008, 10:51 AM:

I would never go to a PC-based scope.

Posted by Mark Gulbrandsen (Member # 72) on 08-01-2008, 11:20 AM:

quote: Louis Bornwasser
Both Fluke & Tek sales angineers tried to properly display the Dolby Digital waveform and struck out (badly).

I don't know Louis... The days of real Tektronix field engineers are long over. The old guys koew theor stuff... the new bunch are more sales then engineering. There are indeed digital scopes that do work. They are widely used in broadcast today and more than capable of displaying anything you throw at them... just expect to spend upwards of 7 grand to get one that'll do the stuff we need. The less expensive Tektronix digital and Fluke scopes just don't cut it for more than general purpose... and they do work well for digital circuits which is the world we now live in.

I do however agree that Ebaying a used 100 mhz Tektronix scope is the best way to go for most tecnicians... but ya have to be careful there too!! It can be more difficult to get parts for later Tektronix CRT models than it is the earlier models.

Mark

Posted by Louis Bornwasser (Member # 3063) on 08-01-2008, 08:57 PM:

Agreed! We bought 5 identical scopes for about $175 each. (Also bought 3 spare Abacus analyzers, just before they stopped making them.) Louis

Posted by Noel Mackisoc (Member # 4852) on 08-31-2008, 01:58 PM:

I bought an OWON PDS5022S-BAT for $395.00 new from their dealer here in NJ. 25MHz. Two x1/x10 probes. Battery/AC. Very light and nice large screen. Intuitive--up and running in about 5mins out of the box.You can look it up on their site www.owon.com.cn.

It's not a Tek or Fluke, but it works well, easy to use, and I'm happy with it. Have used for a-chain, Dolby reader alignment and a few other tasks in and out of shop. I'd give it 4+*.

Hope this helps.

Posted by Troy Hilsman Powell (Member # 4326) on 08-31-2008, 02:48 PM:

Call astrotoo electronics.I think it is astrotoo.com You would be surprised at what they have.Been there done that great store.

Posted by Fernando Cavallero (Member # 4241) on 08-31-2008, 05:49 PM:

Thanks for your data Noel. The most critical views in digitals are the A-chain azimuth (usually plenty "crazy dots") an the "grass" inside the video sygnal. In digital scopes the focus is the high bright grass instead of the less bright in analogs.
How do that sygnals look? Are they enougt similar as in analogs?
Regards

Posted by John Walsh (Member # 168) on 08-31-2008, 11:04 PM:

OK, here’s a question: Let’s say you have used a good analog scope for a while, and already ‘know’ what to look for when doing SR-D and optical A-chains. Would a less expensive digital scope (like Noel described) be good enough when doing a just a digital SR-D voltage check, or an optical A-chain alignment? What I mean is, could you use a simple digital scope for everyday stuff, and only bring out something good like a Tek 465 (all bow your heads in reverence [Wink]

when there is a ‘real’ problem?

Hey, Noel!

Posted by Mark Gulbrandsen (Member # 72) on 09-01-2008, 12:38 PM:

Noel's link is broken but OWON can be googled You could use it for sine/square waves and looking for audio/digital signals for sure and assumming you have a clear view of bottom to top distance of the video waveform but it may not necessarily trigger well then yes it could be used for Peak to Peak video voltage settings. It only has a 100mS/s sample rate which couldn't be classified as very high for looking at composite video. The best way to see if it is really uable would be to set the P to P level with the digital scope and then verify the digital scope with a known good analog scope. Still only the very expensive digital scopes are really any good or able to present a really accurate waveform, you must have a pretty dang high sampling rate. The Tektronix TDS 210 which is an older low end 60mhz digital scope has a 1GS/s sample rate, while the higher end digital scopes do 40GS/s sample rates and beyond!!! There are some interesting videos on the Tektronix site showing different scopes(Tektronix, Agilent, LeCroy, all high end) displaying complex waveforms that is pretty interesting.
Tek Scope Info Page

Mark

Posted by John Walsh (Member # 168) on 09-01-2008, 01:05 PM:

Try this link for Noel's scope:

Digital Storage Oscilloscope Owon PDS5022S

Yeah, I was just thinking that most of the time you are just checking the optical azimuth or the SR-D level.

Posted by Mark Gulbrandsen (Member # 72) on 09-01-2008, 03:20 PM:

Basically its intended for just general purpose use, and I'd buy it from someplace that also offers a 30 day return. This way if it can't even begin to see the SRD waveform or at least the waveform height on screen isn't correct or usable then you can return it.

It looks like something they'd sell at Frys. If you have one near you or will be near one in the futire you may be in a position to compare it with the Tektronix stuff... which they also normally have on display too. Just keep in mind that the stuff there is the low end Tektronix stuff...

Mark

Posted by Fernando Cavallero (Member # 4241) on 09-01-2008, 09:07 PM:

Mark, please tell us how does it work. And... if you returned it after the 30 days!
John you are right. In SDR or azimuth we are looking for maximun or minumun conditions. Best bright or a more narrow graph. So which is the ideal equilibrium between cost vs behavior? That´s the question.
Regards Fer

Posted by Noel Mackisoc (Member # 4852) on 09-12-2008, 11:01 AM:

The only thing I noticed with the OWON was the trigger was a bit flukey (notice: not capitalized!) and needs some diddling to get stable. But it was certainly good enough for my purposes.
And, yes, as others have mentioned, so long as you know what you're supposed to be seeing, an inexpensive tool, so long as it's not junk, is a nice and cost-effective addition to the ever-weightier toolkit.
Cheers all.

Posted by Danial Simmonds (Member # 4638) on 09-30-2008, 06:12 AM:

Ive been using a Tektronix Analog osciloscope for about 2 years but few months ago we change to a small Tektronix osciloscope which is a digital one its small compact and easy to carry...

Makes life much more easy... it can even save the your alignment as a picture image for reporting.

Regards
Dan

Posted by Fernando Cavallero (Member # 4241) on 10-02-2008, 09:30 PM:

Dan, Which model did you buy? Thanks