Film-Tech Forum ARCHIVE: recommendation for a good Oscilloscope

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Posted by Anhtu Vu (Member # 7689) on 07-16-2018, 07:01 PM:

Can someone recommend a good oscilloscope that's portable, can operate on battery (not a must but definitely a big +). It will be used mainly for calibrating the CP650 so i guess a 20 Mhz model should be plenty.

Just in case someone recommend a sound card oscilloscope, i tried the Zeitnitz app and not convinced about its accuracy, besides, it's a pain to lug around a laptop/sound card just for a quick check.

Thanks

Posted by Scott Norwood (Member # 30) on 07-16-2018, 07:11 PM:

Pretty much any 2-channel 20MHz model will work. You can find these all day long for $100-ish on Ebay. The calibration is non-critical for optical sound alignment. I have a Leader something-or-other that works fine. The smaller and more portable models will be somewhat rarer and more expensive.

The general consensus seems to be that the Tektronix 465 is the ne plus ultra of oscilloscopes for this sort of work, for whatever that is worth. You probably don't want a digital scope.

Regardless of the model you choose, you will need a set of cables for BNC (on the scope) to Pomona "pin tip" connectors (on the CP650). I also got got some crimp-type pin tip connectors and made a pin-tip to 1/4" cable to connect my RTA to the processor. (The separate RTA is probably not actually necessary for the CP650, though).

Posted by Monte L Fullmer (Member # 2797) on 07-17-2018, 03:13 PM:

The 465 units were the best around.

Sorry, don't think you can get a battery operated O'scope due to the power requirements of the CRT.

Posted by Anhtu Vu (Member # 7689) on 07-17-2018, 03:23 PM:

How about this model?
https://www.tek.com/oscilloscope/tbs1000-digital-storage-oscilloscope

What's so bad about digital oscilloscope ?

Posted by Dennis Benjamin (Member # 1137) on 07-17-2018, 04:28 PM:

Or you could build your own:

The link

An oscilloscope is a laboratory instrument commonly used to display and analyze the waveform of electronic signals. In effect, the device draws a graph of the instantaneous signal voltage as a function of time.

Oscilloscopes are used in the sciences, medicine, engineering, and telecommunications industry. Oscilloscopes are very essential and best friend for students, maker, hobbyist and electronics enthusiast. While a digital multimeter can help you measure steady state and RMS (Root-Mean-Square) voltages, the oscilloscope can not only measure peak-to-peak voltages, but more importantly provide timing information on your signal. For instance, have you ever been working with an Arduino controlling a servo motor that has to have just the right pulse width modulation in order to spin clockwise instead of counter-clockwise? During your programming, you may have wondered just how close the pulse width was to what was needed. With an oscilloscope you can measure these pulses. When dealing with analog signals, you can use an oscilloscope to see how close you are to the frequency you need or measure what frequency you need to filter. With so many digital electronic projects, timing between signals is extremely important. Therefore, having an oscilloscope is essential but unfortunately they are very expensive.

You can find several DIY oscilloscope in Internet and some links are provided below:

1. PC sound card based oscilloscope

http://homediyelectronics.com/projects/howtomakeafreesoundcardpcoscilloscope/

https://www.instructables.com/id/Use-Your-Laptop-as-Oscilloscope/

http://makezine.com/projects/sound-card-oscilloscope/

2. Arduino based oscilloscope

https://www.instructables.com/id/Arduino-Oscilloscope-poor-mans-Oscilloscope/

http://www.miupanel.com/Projects/Arduino-Advanced-Oscilloscope

https://www.instructables.com/id/Girino-Fast-Arduino-Oscilloscope/

https://www.instructables.com/id/DIY-USB-OSCILLOSCOPE-IN-A-MATCHBOX/

3. CRT TV based oscilloscope

https://www.instructables.com/id/Fully-Functional-Television-Oscilloscope/

https://www.instructables.com/id/Mini-TV-Oscilloscope/

https://www.instructables.com/id/How-To-Make-A-CRT-TV-Into-an-Oscilloscope/

4. Smart phone based oscilloscope

https://www.instructables.com/id/OscilloPhone-Use-your-Smartphone-as-an-Oscilloscop/

https://www.instructables.com/id/A-Preamplifier-for-Smartphone-Oscilloscopes/

http://projectproto.blogspot.com/2010/09/android-bluetooth-oscilloscope.html

5. Raspberry Pi based oscilloscope

https://www.instructables.com/id/PiMSO-A-Raspberry-Pi-based-Wi-Fi-Oscilloscope/

http://www.open-electronics.org/turn-your-raspberry-pi-in-an-oscilloscope-with-bitscope/

All of those oscilloscopes have their own pros and cons. Most PC and Arduino based oscilloscope can not sample more than several kilohertz. Sometimes PC based oscilloscope can burn your computer motherboard. Previous Raspberry Pi based oscilloscope required special hardware. I will show you step by step guide how to build a Raspberry Pi based oscilloscope without special hardware. I would like to thank Mr. Daniel Pelikan who first published the idea in the MagPi magazine, Issue 24.

Posted by Monte L Fullmer (Member # 2797) on 07-18-2018, 02:08 PM:

quote: Anhtu Vu
What's so bad about digital oscilloscope ?

Digital units doesn't trace as accurately and refresh as fast as the older CRT based units.

Digital is nice, but Analog still comes out winning.

Only area were digital does win in is with Digital MultiMeters, esp with reading volts and amperage.
This is where the numbers can be displayed in the dot one thousands. An analog VOM can't show this accuracy.

-Monte

Posted by Scott Norwood (Member # 30) on 07-18-2018, 07:22 PM:

What Monte said. Digital scopes have a certain amount of latency that is not present in analog models.

I do like the convert-your-TV-into-an-oscilloscope instructions, even if carrying a TV set from cinema to cinema is a bit impractical. I wonder if there is a way to configure this to take two inputs....

Posted by Marcel Birgelen (Member # 6801) on 07-18-2018, 07:30 PM:

Really?

For simple audio measurement, do yourself a pleasure and go for a digital oscilloscope.

There might still be a very limited amount of applications were an analog scope might outperform a digital one, but for anything someone usually does in this field of work, I can't think of a single one of them.

A digital scope has numerous advantages:

- They're much compacter and lighter than their analog counterparts, because today they all use LCD screens instead of heavy CRTs.
- Since they're far less power hungry, there are lots of models that can run on battery.
- A digital scope can store the data it captured, you can export this data and often there are functions to load in some external reference data.

So, now the disadvantages:
- All digital scopes have some latency, although I still need to find an application were this latency really creates a problem...
- A digital scope uses digital samples, so the curve it plots is not as perfectly smooth as the analog one. It also displays the curves on a raster display, not on a CRT screen with directly driven electron beam. Given sufficient resolution though, this is almost never a problem.

In order to go for accuracy, I'd always go for one of the known brands, not for some self-built RasPi project or some hardware-software interface. The "big brand" oscilloscopes usually come pre-calibrated and pre-tested, so you can ensure some levels of accuracy.

Posted by Gordon McLeod (Member # 33) on 07-19-2018, 08:51 AM:

Analogue is still the best if aligning a SRD reader as the latency of the digital ones make alignment troublesome
For the optical and mag the D2 has a good scope built into it

Posted by Anhtu Vu (Member # 7689) on 07-19-2018, 02:02 PM:

Marcel..can you recommend a digital oscilloscope ?

How about this one...How about this one?
https://www.tek.com/oscilloscope/tbs1000-digital-storage-oscilloscope

Posted by Gordon McLeod (Member # 33) on 07-19-2018, 03:19 PM:

Rigol DS1054 is a good digital scope but i said if you are aligning a SRD digital reader you need a 20MHz analogue scope

Posted by Sam D. Chavez (Member # 1841) on 07-19-2018, 03:48 PM:

Even doing A chain alignment on an optical soundhead is best done with an analog scope. Azimuth using x/y is hard to do with a digital scope because of the latency and very easy to see on an analog scope. I still use a Tektronix 212 scope for this. Also a very nice portable leader, of course no longer made.

Posted by Dave Macaulay (Member # 813) on 07-19-2018, 09:12 PM:

I have used both and agree that analog is better for SRD alignment. For analog digital is ok but the x/y plot is just cleaner on the old 465 than on any digital scope I have used. I have not tried a really top-dollar digital one though, and the 465 was in that league when new so the comparison may not be fair. Its triggering is amazing compared to the digital ones I used, including some pretty nice Tek models.

Posted by Steve Guttag (Member # 268) on 07-20-2018, 05:49 AM:

I'll say that for analog, the "scope" that is in the D2 analyzer is good. No problems on azimuth or lateral alignment (via Buzz track).

I'm with the others on SRD and using an analog scope...and like others, I've settled on a Tek scope but most any 20MHz or better will work.

Posted by Gary A. Hoselton (Member # 3447) on 07-23-2018, 01:53 PM:

I like my Tektronix 465. Beam Intensity pot has gotten intermittent, a cubical Allen Bradley circuitboard mount pot. I loosened it and sprayed Quietrol in it and helped some, but didn't fix.

Posted by Mark Gulbrandsen (Member # 72) on 07-23-2018, 09:18 PM:

Stay away from digital scopes for sure! Been there, done that... Both Tektronix and HP. You'll never be able to set up an SRD reader or penthouse using a digital scope because few of them can sample fast enough, and even looking at L-R alignment film can be futile.. unless it's a very high end expensive digital scope...

Mark

Posted by Gordon McLeod (Member # 33) on 07-25-2018, 09:14 AM:

I have a compact Leader 60mhz scope that i still carry around