100MHz oscilloscope vs 70MHz oscilloscope for home lab, what is the difference? - Page 1
Forum section: electronics / general

author: matrixofdynamism
author_rank: Regular Contributor
timestamp: July 09, 2014, 06:42:18 pm
content: Now when we are designing some complex circiuits e.g with multi-gigabit transcivers vs low speed circuits e.g RS232 module, it makes a lot of difference which oscilloscope we have and use.For ahome labI want to buy "Rigol MSO1074Z 4 Channel Digital Oscilloscope 70MHz Bandwidth 1GSa/s with 2A+16 Digital Channels" but am confused if I should rather get "Rigol MSO1104Z 4 Channel Digital Oscilloscope 100MHz Bandwidth 1GSa/s plus 2An+16Digital Channels" for 19% more money. One is 70MHz and the other is 100MHz. Should I get the 100MHz instead?Besides this, by adding some more money one can get a 25MHz signal generator as well within the scope. Is this really better than having a separate signal generator?I am going to place the order very soon but am confused here.

author: echen1024
author_rank: Super Contributor
timestamp: July 09, 2014, 07:32:46 pm
content: Put your S/N into the keygen and get 100MHz.

author: DavidDLC
author_rank: Frequent Contributor
timestamp: July 09, 2014, 07:34:08 pm
content: The difference between a 100 MHz and a 70 MHz oscilloscope is 30 MHz.Solved.David.

author: matrixofdynamism
author_rank: Regular Contributor
timestamp: July 09, 2014, 07:43:16 pm
content: haha, what I meant to ask is, is it worth spending more money and get the 100MHz scope or not? Is it worth spending extra money and get the built in wave form generator or not? This is what I want to know. This all is for a home lab.

author: kolonelkadat
author_rank: Regular Contributor
timestamp: July 09, 2014, 07:48:29 pm
content: the way I see it is like this.If youre a business, you need the calibrations and certifications and documentations, so you buy the version that does what you need for the job; price is irrelevant.If youre a hobbyist, you just need the machine to work. So you buy the down market version for as cheap as possible and unlock any upmarket features for free.

author: David Hess
author_rank: Super Contributor
timestamp: July 09, 2014, 09:29:55 pm
content: The difference between 70 MHz and 100 MHz input bandwidth will not be significant in almost all applications.

author: matrixofdynamism
author_rank: Regular Contributor
timestamp: July 09, 2014, 09:39:53 pm
content: What about built in signal generator, is it worth paying extra £ to get it?

author: mrflibble
author_rank: Super Contributor
timestamp: July 10, 2014, 06:08:52 am
content: IMO you are better of getting a separate signal generator.

author: nowlan
author_rank: Frequent Contributor
timestamp: July 10, 2014, 06:40:40 am
content: I think the rule is get 5x the speed of your fastest signal you will be looking at.Should be fine for arduino, audio, etc.Starts to become a problem with the fast ARM processors.Im not sure how it works with RF stuff. People been doing that with slower scopes previously.

author: pickle9000
author_rank: Super Contributor
timestamp: July 10, 2014, 07:08:14 am
content: Quote from: matrixofdynamism on July 09, 2014, 09:39:53 pmAn in scope signal generator is handy but external ones are more mature. Just look at the specs.

author: EEVblog
author_rank: Unknown
timestamp: July 10, 2014, 07:25:16 am
content: Quote from: matrixofdynamism on July 09, 2014, 07:43:16 pmI don't think so.The scope doesn't magically stop working at 70MHz or 100MHz, your displayed signal level just drops.So there is essentially very little you can do with a 100MHz that you can't do with a 70MHz scope.Spend the extra money on something else.

author: TriodeTiger
author_rank: Regular Contributor
timestamp: July 10, 2014, 08:44:07 am
content: Quote from: nowlan on July 10, 2014, 06:40:40 amQuote from: matrixofdynamism on July 09, 2014, 07:43:16 pmQuote from: EEVblog on July 10, 2014, 07:25:16 amWith a 70MHz scope, If you are viewing a 14MHz clock signal (the Arduino has a 16MHz clock?), your 5th harmonics of the square wave of the clock will be attenuated at 3dB. The square wave may look very square when in reality the sum of the further harmonics are not captured and represented properly, which is where a better scope may come in handy.IMO a spectrum analyser (even an SDR?) would be a better tool - why spend all the extra money to get a possibly gimmicky function generator and see signals slightly more than the last, when an SA or even radio can tell you much more for much less?

author: matrixofdynamism
author_rank: Regular Contributor
timestamp: July 11, 2014, 06:28:48 pm
content: Thanks for the replies guys, after thinking over it I have placed order for my new oscilloscope. I shall buy a separate signal generator instead. This one looks good:http://www.rigol-uk.co.uk/Rigol-Waveform-Generator-DG1022-p/dg1022.htm

author: Galenbo
author_rank: Super Contributor
timestamp: July 12, 2014, 10:18:56 am
content: I have the same signal generator (who not?)It works.The only stupid thing is the form factor, I would have liked the same form as the scope.Why do you want the MSO istead of the DS?Digital, protocols, decoding,... seems to me something for a separate machine, better upgradable, filtering, report generation,...Whats's the price of a separate USB-digital analyser with all the specs the MSO has?

author: josem
author_rank: Regular Contributor
timestamp: July 12, 2014, 01:08:12 pm
content: Quote from: Galenbo on July 12, 2014, 10:18:56 amI'm kind of figuring this out myself, so I may be incorrect, but to me a MSO biggest advantage is easy cross-triggering between the analog and digital channels, which would be difficult to achieve with a separate LA.USB analysers in particular (I'm thinking Saleae) don't seem to have a trigger out that I could connect to a scope, perhaps because they have all the processing+USB delays and are not in sync with the signal.There are of course hardware LA with external trigger ports but those are expensive and it would mean setting up two different systems to configure and record from.So the MSO with the the cross triggering seems a easy solution if I'm looking for sporadic problems with certain commands sent to a microntroller, or perhaps measuring current bursts in reaction to specific commands,The specs on the Rigol MSO are also on the high end, 16 Channels 1GSa/s, and I think in raw specs it surpasses even the $300 16 port Saleae. On the other hand the Rigol as standard doesn't do protocol decoding that the Saleae does and the option is quite costly (unless the Rigol is hacked, of course)Again this is just my newbie opinion...

author: David Hess
author_rank: Super Contributor
timestamp: July 12, 2014, 05:29:59 pm
content: Quote from: josem on July 12, 2014, 01:08:12 pmWhen called for, I have found this to be an incredibly useful function on an oscilloscope whether analog or digital.QuoteI have noticed this before. I think the problem is that the FPGA based triggering commonly used now only recognizes the trigger conditions after other processing so by then it is too late to generate an immediate trigger output. Analog oscilloscopes often have gate out signals which implement the same thing and some old DSOs do as well with latency in the 10s of nanoseconds and low jitter.QuoteOlder generations would recognize this function as a word recognizer and it was a common secondary function in old logic analyzers but it can be implemented by itself were it becomes something like a poor-man's logic analyzer. They are incredibly simple to implement but I have not seen one outside of an MSO in a while. They were often available as an option on old DSOs and even analog oscilloscopes. Latency on the optional word recognizer for my old DSO is in the tens of nanoseconds range and jitter is below the level that a general purpose oscilloscope can measure.QuoteIn the past when I did not have a word recognizer available, I often added some test logic to generate a trigger or relied on the microcontroller to flip an output line directly under software control.

author: mrflibble
author_rank: Super Contributor
timestamp: July 12, 2014, 07:17:22 pm
content: Quote from: David Hess on July 12, 2014, 05:29:59 pmIf only they did do (proper) fpga based triggering, then you'd have a usable trigger for your scope. Things like sump and openbench logic sniffer do have some basic triggering, but anything more than the basics has to be done client side. As in after the capture.And the sad thing is ... the openbench logic snifferdoeshave advanced trigger functionality in the newer firmware. But no support for it in the java based client.At least not when last I checked it a year or so ago.... *checks* ...Nope, still no advanced trigger support. Ah well, guess I'll check again next year.Incidentally, for those rolling their own ... you can use the above core + add your favorite chipscope ILA + trigger conditions to get decent triggering and export the trigger to a spare fpga IO for your scope. Beats basic triggering. And for bonus points you get test signal generation as a free feature.

author: dannyf
author_rank: Super Contributor
timestamp: July 13, 2014, 10:22:26 am
content: Quote30Mhz?For most things, you will hardly notice much difference.

author: Galenbo
author_rank: Super Contributor
timestamp: July 13, 2014, 04:04:40 pm
content: Quote from: josem on July 12, 2014, 01:08:12 pmThanks for your answer, Myself I just never needed it, but liked the digital loggers for their protocol analysis.If anyone else knows other uses of a MSO, or workarounds, please tell me.