Oscilloscope Suggestion Request Thread

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Hi there, haven't posted in a while. Just started a new job and I'm building a lab, figured ask the pros this question (that's you guys).

I am concerned with monitoring/viewing waveforms of wifi transfer with an oscilloscope. The BitRate is 4,500,000 Bits per Second for the data we will be sending. What is the minimum Oscilloscope bandwidth needed to view the bits clearly?

We can't afford a logic analyzer and I think a 1GHz scope would be overkill for this application and way too expensive. How many Hz should my scope be able to do minimally to be able to view some data. If you could suggest a specific scope that is low cost and a 2 channels/more, I'd appreciate it. So far I've looked at Tektronix scopes around 40MHz but I'm not sure if this is 'fast' enough. I'd like to go as cheap as possible but still have some sort of reputable brand with a warrant.

Thanks!!!

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To monitor use a serial protocol analyzer. AVR implementation = Bus Ninja, PIC implementation = Bus Pirate. Likely 'Bus Blaster'.
An alternative is a logic analyzer like Open Bench Logic Sniffer. http://sigrok.org/wiki/Logic_Analyzer_Comparison

For signal analog quality, a scope. IIRC, rule of thumb for bandwidth is at least to the 5th and preferrably the 7th harmonic. Better is to have a spec'd rise/fall-time then compute the required bandwidth (Probing High-Speed Digital Designs by Dr. Howard Johnson).
Pricing rule of thumb is 10KUSD/1GHz then add probes' price.
2 channels minimum, 4 is good.
Skip the logic analyzer option unless you really need the integration with analog.
Consider a display-less/USB scope; Pico Technology appears to be good.
Think growth (i.o.w. today's signal frequency is X, tomorrow's signal frequency is predicted to be n*X).

For RF quality, a spectrum analyzer. One low cost one is http://www.spectran.com/. May be better to rent one.

"Dare to be naïve." - Buckminster Fuller

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Do a search in this sub-forum: there have been several threads on this subject.

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tessa and Tina, You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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Ok I'll consider it resolved, thanks gchapman! thanks Plons!

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Presumably your are talking about a DSO, not an analog CRT type O'scope.

In addition to the Bandwidth discussion, above, (and my rule-of-thumb was 10th harmonic of the primary frequency component, (but it depends on the signal source, and how good is good enough), one can approach it from the other end.

Assume you are trying to capture a data packet on the scope.
Assume it is not a repetative signal, so you only get one shot at recording it.

How many samples do you want painted on the screen to display the image?

This isn't about Nyquist-Shannon sampling and reproducing a repetative signal, this is about visually looking at the signal on the display.

One sample per bit period, (hopefully triggered to sample somewhere in the "middle" of the bit period), would act like a logic analyzer and give you a series of high and low dots for the pulses. Minimally useful, if at all, in practice.

10 sampes per bit period would give you plenty to see each bit period, more than needed for packet characterization and decoding.

Somewhere in the middle is the compromise. With a 4.5 M bits/sec data rate, your sampling rate, (one shot pass), is going to be over 2 GS/Sec.

Then start looking at the DSO's memory size, how long a sample can it record?

You are out of the low-end scopes performance range.

JC

Cross-posted... Maybe I should learn to be more concise, or to type faster!

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Is this a digital 4.5Mbps signal? Or are you looking at an analog signal with 4.5Mbps of data encoded on it?

Is the data rate constant? In other words, will it sometimes be 4.0 Mbps and sometimes 4.7Mbps?

I capture SDRAM signals at 125MHz on a 500 Msps logic analyzer. It's very, very tight. But it works in a pinch because it's an even multiple.

Probably for a 4.5Mbps analog signal you want a mininum of 50Msps, and 100Msps is better.

If this is a digital signal, the 100Msps will be plenty good.

Looking on the gabotronics scope list, there's a $350 100Msps scope + logic analyzer with 2Mbyte buffer that'd probably fit the fill.

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Someguy22 wrote:
This caught my eye for various reasons. Also, open source.

http://www.buy.com/prod/new-arm-dso203-nano-v2-quad-pocket-digital-oscilloscope-for-electronic/222441646.html


I could not find the specs (drowned by sites who want to sell it), but found this review. It reflects my opinion well:
Quote:
Nice toy, mostly useless...
With only one channel and no external sync input, it is very hard to view a non-recurrent signal. Also, the controls are baffling, to say the least, consisting of only four push-buttons plus an 'OK' button: to change one setting one has to cycle through every other settings in a seemingly more or less random fashion. The probe is very flimsy and mine is stuck in the open...

If you want to to a job you need a tool, not a toy.

Markus

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Quote:

With only one channel

It says "four channel"? (BTW a lot of competition to supply DSO203 on ebay)

One example on ebay:

http://www.ebay.com/itm/NEW-4-CH...

says:

Quote:
Feature

1. Pocket size and light weight

2. Two 72Mhz analog channels and two digital channels

3. Signal Generator

4. Auto Measurement

5. Various Triggering Option

6. Easy waveform storage

7. Firmware upgrade

8. User applications

9. Open source


and under specification:
Quote:
Specification

1. Analog channel * 2 : [CH_A] [CH_B];

2. Digital channel * 2 : [CH_C] [CH_D];

10. Trigger source: CH1/CH2/EXT


In the photos you can see four phonos on the case marked CH-A/B/C/D

Last Edited: Wed. Sep 21, 2011 - 03:02 PM
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ummm, that very link reveals a statement that the item has 4 channels and edge triggering. Don't know where the single channel claim came from but it does not appear to be correct. (I have no knowledge of the device ... just able to read)

Cheers,

Ross

Ross McKenzie ValuSoft Melbourne Australia

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I have this thingy - works as expected, nothing less, nothing more. It has 2 analog and 2 logic channels plus a primitive waveform generator. It's all open source, so some new features/updates appear from time to time. Most discussions can be seen here.

Warning: Grumpy Old Chuff. Reading this post may severely damage your mental health.

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Don't forget memory depth. If you're wanting to capture packets of data, how long will the scope have to be sampling at (at xx Msamples/sec) to capture the data you want, and hence how deep does the scope memory need to be?

For our most recent scope purpose, scope memory depth was a critical factor. Many of the cheap scopes have quite shallow memories.

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Like I said, I was swamped by ebay offerings, and did not found an official spec sheet. The OP seems to need a tool for professional use. I don't think this qualifies.

That it is open source has some advantage for hobbyists. I've seen it with the 'open bench logic sniffer' an logic analyzer also available from seeedstudio. The software did evolve considerably over time, it has become a lot better over the last year. I expect this device to evolve the same way. If it is sold in sufficiently high numbers an active and productive community will develop, if it has not done so already.

Markus

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There's a long thread on the Seeed studio site about the bandwidth of the DSO Quad. This scope is delivering bandwidth around 10 MHz...it can show a 1 MHz square wave as square. In the thread folks are asking for their money back as they feel this was sold as a 35 MHz bandwidth scope.

http://www.seeedstudio.com/forum...

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I can't speak for its suitability for this application, but my 50MHz Rigol DS1052E is both very cheap, and very functional. Rigol make the low-end O'scopes for Agilent, and the unit I have is very responsive and has plenty of features including a decent memory depth.

- Dean :twisted:

Make Atmel Studio better with my free extensions. Open source and feedback welcome!

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Just noticed that the local "electronic components and instruments dealer" ELFA offers a LeCroy WAVEACE 101 at under $US 100 (SEK 5000). It's 2 ch 50 MHz (500 MS/s). Full color screen, etc: https://www.elfa.se/elfa3~se_en/... .

I always thought that LeCroy was the cream of the cream of 'scopes. Only time I was allowed near one (1 meter limit) I was told it cost half a million SEK (approx 1K US$).

Just a few days left - and I do not own a 'scope yet. Opinions?

EDIT: I mistyped the US$ price.. US$ 1000! (not 100)

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Last Edited: Fri. Sep 30, 2011 - 06:57 AM
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I don't know the product in question. If you had asked me about the price of LeCroy scopes I would have said the entry product line starts at $10000, so I'm pretty amazed to see the LeCroy name on a <$100 product. The specs look quite decent (http://www.lecroy.com/oscilloscope/oscilloscopemodel.aspx?modelid=2118). The price at Farnell is around $800, too.

Can you buy one for me too ?

Markus

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The $US 100 must be for the shipping box. I see $4995.00 for the real thing at the ELFA link.
More coffee Johan!

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The 4995 is in Swedish Kroners (SEK). One SEK is worth 0.15 USD from Google. So the scope costs $750. Should have looked that up earlier...

At that price it makes sense to compare with the competition. I suspect, that LeCroy, like other manufacturers, buys an OEM scope in China and slaps their label on it. So you may well be better off buying the scope from the original manufacturer without the uplift for the Label.

A scope is a good investment. Many things are much easier with scope than without.

Markus

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Well, I finally found the "change country" button. It converts the price to 525 Euros even when selecting the US. I'll keep my Tek 3012 though. Where did Johan find the $100 price?

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JohanEkdahl wrote:

I always thought that LeCroy was the cream of the cream of 'scopes. Only time I was allowed near one (1 meter limit) I was told it cost half a million SEK (approx 1K US$).

According to this
http://www.electronicskb.com/Uwe...

Quote:
LeCroy's cheapest scope series, the WaveAce series are just rebadged
Atten ADS1000 series

Like Dean i have a : 50MHz Rigol DS1052E (ebay) , and also a "Real" DS1102E. My friend offered to bring one back from Shanghai for 400€. So i had to ... :-) ... And the 50Mhz (i haven't gotten around to convert it yet) now lives in the summerhouse.

And with a bit of "Magic" it seems like it's still posible to convert the DS1052E to a DS1102E (100Mhz)

This offer is rather attracive (for Johan , as its in EU) , so no VAT or Posten (VAT handling) charges.
http://www.ebay.de/itm/Digital-o...

/Bingo

Last Edited: Fri. Sep 30, 2011 - 07:18 AM
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Ohh btw:

When i bought my DS1052E , i also got a cheap freq cntr for the summerhouse from same seller.
http://www.ebay.de/itm/LW-TFC-27...

The TCXO was "China" aka "A 13Mhz Xtal with a transistor as heater" , and the adjustment was broken.

Then i got a hint about these
http://www.ebay.de/itm/Pletronic...

The original TCXO is mounted in a metal can ,on the backside of the chassis , with 3 wires going to the PCB.
5v VCC , GND & Clock.

So i build a replacement 13Mhz OCXO , with the Pletronics ocxo , a separate LM2940 as regulator , a Pot for adjustment & and an 74AC74 as a /2 divider. (Thanx for the guidance KKP) :-)

Now i have an 8 digit ultrastable freq cntr , it is spot-on my 10Mhz Thunderbolt GPSDO Reference within 60 sec.

So if you can live with 8 digits , this is a nice hack.

There is even an M8515 inside , and some day i have to see what goes on on the RX/TX pins :-)

One could hope .....

/Bingo

Last Edited: Fri. Sep 30, 2011 - 08:59 AM
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Quote:

Where did Johan find the $100 price?

Elfa. Follow my link above. SEK 5000 + 25 pct VAT = SEK 6000. Approx US$ 1000.

Oh, I see it now... I missed out on a zero. :oops: Yes, $100 would have been a real deal...

As of January 15, 2018, Site fix-up work has begun! Now do your part and report any bugs or deficiencies here

No guarantees, but if we don't report problems they won't get much of  a chance to be fixed! Details/discussions at link given just above.

 

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

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Rigol make the low-end O'scopes for Agilent, ATTEN (5,7" lcd series) for LeCroy (waveace series). Pay attention to the chassis shape and pushbotton position.
http://www.ebay.com/itm/ATTEN-7-...