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Mrhazeem
26-12-2002, 07:09 PM
I want to know .... What is the difference between Oscilloscope

and spectrum analayser ...? my question is may be stubid but i'm

new to gsm repairing ...!!

herbalviagra
19-01-2003, 06:52 AM
Oscilloscopes show signal in the time domain, Spectrum Analyzers show signal in the frequency domain.

Timing/Logic analyzers are basically oscilloscopes stripped down to show a graphical representation of signals in the time domain from many sources. Some do have the option to show a channel or two with some resolution, similar to an oscilliscope, but are most useful for seeing traffic and transactions on a bus or similar data path. Also good for debugging state machines, combinatoral logic, shit like that.

oscilloscopes are more to find out the quality of a periodic signal at given intervals (some specific main frequency), but can be set up to check for noise distribution, and gan do limited logic analyzation depending on how many channels (inputs) you have. You can test for logic signals and capture single event transients with them as well, but they're sort of general purpose equipment.

Spectrum analyzers will show the frequency composition of whatever signal you've got hooked up to it, at any instant in time, or for some amount of time depending on how deep of record length you can keep. But each instance is the composition at a single point in time, unless you are running histograms for specific intervals of time.

Most of the new ones are PC capable, or have basically PC functionality embedded within them, so that you can get very deep memory and post processing, all onboard.

Oscilloscopes are used more for continuous measurements...

need more clarity? I can point you at info sources, and go a little deeper if necessary.

-herb

mkwatis
19-01-2003, 01:13 PM
Originally posted by herbalviagra
Oscilloscopes show signal in the time domain, Spectrum Analyzers show signal in the frequency domain.

Timing/Logic analyzers are basically oscilloscopes stripped down to show a graphical representation of signals in the time domain from many sources. Some do have the option to show a channel or two with some resolution, similar to an oscilliscope, but are most useful for seeing traffic and transactions on a bus or similar data path. Also good for debugging state machines, combinatoral logic, shit like that.

oscilloscopes are more to find out the quality of a periodic signal at given intervals (some specific main frequency), but can be set up to check for noise distribution, and gan do limited logic analyzation depending on how many channels (inputs) you have. You can test for logic signals and capture single event transients with them as well, but they're sort of general purpose equipment.

Spectrum analyzers will show the frequency composition of whatever signal you've got hooked up to it, at any instant in time, or for some amount of time depending on how deep of record length you can keep. But each instance is the composition at a single point in time, unless you are running histograms for specific intervals of time.

Most of the new ones are PC capable, or have basically PC functionality embedded within them, so that you can get very deep memory and post processing, all onboard.

Oscilloscopes are used more for continuous measurements...

need more clarity? I can point you at info sources, and go a little deeper if necessary.

-herb

please can you give me the info sourses for this?

herbalviagra
19-01-2003, 07:38 PM
Well, actually, that was from memory. I would suggest you go to any of these manufacturers and search for "app notes"

Agilent
Tektronix
HP
LeCroy

and any other major manufacturer of test gear.

I actually have many application notes that are no longer maintained or have been obsoleted by the manufacturers, and are no longer publicly available on the web. They have been phased out because they are for gear that is no longer being offered, the "latest and greatest" technology has changed, political reasons, lack of funds to support all the legacy notes, or any of a myriad of reasons, but they still often contain more detail regarding general test techniques, application and theory, than new ones.

I'll try to find some links to info out there, Agilent has picked up and updated many of the old HP docs and tutorials, although you can still see the HP logos on them.

It seems that most manufacturers have lost sight of the fact that the burden is upon them to educate their customers in an unbiased and professional manner in order to develop technical credibility and knowledgeable customers and thereby gain customer confidence in the company being able to design real and accurate test gear and create a group of users to sell in to.

It takes a lot of reading, and understanding of math and applied electronic theory. In some cases, the applications cannot be understood without a great deal of higher mathematics.

For what we want to do here, accurate descriptions of how to set up test fixtures and a sort of real-world, simplified "why it's done this way" (as well as some blind faith in technology ;-) ) should be enough to meet the goals of the forum.

I'll poka around and see what I can come up with, IIRC Agilent still had up some great tutorials...if they aren't available on the web, you may be able to order them. Almost all this information is available at no-cost from the manufacturer. Most of the websites have forms you can fill out online to get the info if it's not accessable via the web or you have troubles finding it.

Again, manufacturers put some effort into educating their potential customers, and since there are so many technically literate people out there, there's not much bogus or predatory focus on the info. Usually, they try to set up advantages and then sell their gear into those aspects that they are trying to make seem important...always look for hard specs, test setups, test circuits, environments that the gear was qualified in when they were proving a spec...most mfr need to provide a lot of this info for regulatory compliance, so the test data is out there somewhere and you can usually get it if it's not already specifically listed in the data sheets or manuals.

I'll continue this in a follow up and post some links to what I can find...

-herb

herbalviagra
19-01-2003, 08:00 PM
agilent's main library page
http://we.home.agilent.com/cgi-bin/bvpub/agilent/library/cp_Library.jsp?CT=AGILENT_COLLECTION&NAV_ID=-11145.0.00&NEWCCLC=ZZ&JPID=/find/xbv_library

link to scope applications page
http://we.home.agilent.com/cgi-bin/bvpub/agilent/expandedresults/cp_ExpandedResults.jsp?LANGUAGE_CODE=eng&NAV_ID=-11145.0.00&NEWCCLC=ZZ&COUNTRY_CODE=ZZ&CT=AGILENT_COLLECTION&contentType=Editorial&entityType=ED30%2CED33%2CED34&subjectSelect=SUB-047

As you can see, the "8 more hints to better scope measurements" compared to the original "8 hints to better scope measurements" demonstrates what I was mentioning when I was saying that often older app notes are more useful because the newer ones are becoming more of "brochures" than "tutorials". I hadn't seen that yet. Although there is some information there, I'm pretty disappointed.

link to spectrum analysis page
http://we.home.agilent.com/cgi-bin/bvpub/agilent/expandedresults/cp_ExpandedResults.jsp?LANGUAGE_CODE=eng&NAV_ID=-11145.0.00&NEWCCLC=ZZ&COUNTRY_CODE=ZZ&CT=AGILENT_COLLECTION&contentType=Editorial&entityType=ED30%2CED33%2CED34&subjectSelect=SUB-069

link to timing analysis page
http://we.home.agilent.com/cgi-bin/bvpub/agilent/expandedresults/cp_ExpandedResults.jsp?LANGUAGE_CODE=eng&NAV_ID=-11145.0.00&NEWCCLC=ZZ&COUNTRY_CODE=ZZ&CT=AGILENT_COLLECTION&contentType=Editorial&entityType=ED30%2CED33%2CED34&subjectSelect=SUB-075

some of these pages have multiple pages to riffle through. Often I don't like how the page is set up for navigation, so usually I'll start with something like a google search on what I'm looking for, and then just riffle through the links until I find what I need. This is also a good way of rooting out universities and third-party (not the originating source for the app note/tutorial) copies of older app notes...for example...
http://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=app+notes+jitter&btnG=Google+Search
or even
http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&q=app+notes+arm+&btnG=Google+Search

There's so little actual hardcopy out there anymore, that I am very, very, internet dependant for information and continuing my education. The net has turned into my personal library....

:-)

That should give you a little to chew on for a bit. You'll have to poke around and find what you're looking for, but if you poke around for a bit, you will surely find it.

There are many basic electronics tutorials out there, as well, for those of you who can't afford the texts...often course instructors at universities will put labs up in publicly accessible webspace, as well as lecture notes.

MIT has started an "open source education" program that allows anyone to study subjects from MIT and other places, freely, online, with all course material provided. It's still relatively new (<6 months) so it's still building up material.

http://ocw.mit.edu/

-herb