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Show us your square wave

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Rupunzell:
That is not the way test gear was once sold. The hewlett packard or Tektronix sales folks would visit to chat about their latest offerings, bring in the demo as requested then answer ALL related questions to what is and what is not. And.. they did specials if that was a better T & M solution.

*Zero pressure sales..

*Vintage hewlett packard & Tektronix printed catalogs had the price of said instrument and accessories in print.

If there were problems, they were quickly resolved within the designed in limits of said test gear. Post sales support was often good to excellent and most of all had few if any "bugs" that were baked in requiring "updates" to exterminate said bugs. Test gear was expected to do their intended job, function as required with zero grief, day after day, year after year. Yes, they got their periodic calibration and maintenance to help them stay healthy as test gear was considered an investment back then.

That has all changed today to Buy It Now, then toss it out soon as it's out of warranty (Bean counters & investors kinda demand this today). Yes, technology and measurement needs move forward, but keeping perspective on what is actually needed to get that measurement and testing done -vs- the latest and greatest with every fantasy bell & whistle turned into reality in that new box is not always a good thing. Really a matter of knowing precisely what is needed -vs- what is nice to have under the light of an orange moon.



Bernice




--- Quote from: Wuerstchenhund on January 30, 2015, 10:33:49 am ---
I wonder the same. My pet peeves are "Request Quote" buttons. What is hell the problem with just listing how much the damn thing costs? Agilent has prices on the US site but on most variants for other countries (including the UK) all you get is "Request Quote". It's different if I want to order or negotiate but more often than not I find myself thinking that if I have to go through a sales droid to get a simple price that I rather not bother at all.

LeCroy's website is even worse. It lists the base price for some scopes but for everything else I have to through a quote request. Seriously? Why can I configure a luxury car online which comes with hundreds of options, but can't do the same for a scope?

And then there's Tek who's sales droids are even calling me when I dared to download some spec sheet or manual from their website. I guess they must be really desperate these days.

--- End quote ---

joeqsmith:

--- Quote ---That is not the way test gear was once sold.
--- End quote ---
Some of them still come on-site and leave the equipment with us.   I don't like Keysight tossing their sales like they did.  We had Copper Mountain in a while back.  Great presentation, spent the day going over their product.  :-+   



--- Quote ---Looking at this particular DSO's dead time:

10GS/s, collecting 5Ms requires 640ms.   If the PCI bus could handle 60MB sustained, it would require 83ms to move the data or about 13% of the bus BW.   Say the Ethernet can move the data at 50Mb/s which is about what I was getting with the built in board.   So about 6.25MB/second.   Moving 5Ms will require about 800ms.     

If we want to handle the data and not miss any of the little data the DSO does happen to collect, the 100Mb won't cut it.     At 400Mb/s with the 1G Ethernet, this time drops to 100mS.  Maybe enough time to move the data to the modern PC, post process and display it.   

At 10GS/s and collecting 200Ks requires 35ms.   Staying with 60MB on the PCI bus, it would require 3.33ms or about 9.5% of the bus.  The Ethernet transfer would be about 32ms using 100Gb.

For 20GS/second collecting 32MS (max for this DSO) requires 9.486 seconds.    So that is 1.6 ms of data collected out of the 9.486 seconds of total data.  :-DD  Using the same 60MB PCI BW, that's about 533.33ms to move this data.    Or about 5.6% of the PCI bus being used.   

So say 534.93 ms is used to collect the data and move it through the PCI bus to the PC.   There's 8.951 seconds to get the data onto the screen.   Keep in mind, there's no math enabled and only one channel is being used.

--- End quote ---

My old LeCroy Wavemaster 8500A has an Intel P4 2.533GHz with 512KB L2 cache and 2G of RAM installed.  It also has a SSD.

Today I pulled out an old Agilent Infiniium MSO8104A.  This DSO is a little newer but much lower end than the Wavemaster, maybe a 1/4 of the price.    It also uses XP-Pro.  It has an Intel Celeron D 3.20GHz  with 256K L2 cache.    Is has the original mechanical drive in it.     It does however come with a 1Gb Ethernet port.   

Both DSOs have the same FSB speed. 

I repeated the test on the Wavemaster collecting at 5GS/s, 5M samples.  This requires 531 ms.   
Using the Infiniium collecting at 4GS/s, 8.2M samples required 42 ms.    I was actually running some math on the Infiniium and still out performing the LeCroy.   

I tried to run an FFT with the Infiniium and see what it would display at the sample frequency.  They don't seem to allow you to do this.

Wuerstchenhund:

--- Quote from: joeqsmith on January 31, 2015, 03:14:25 am ---My old LeCroy Wavemaster 8500A has an Intel P4 2.533GHz with 512KB L2 cache and 2G of RAM installed.  It also has a SSD.
--- End quote ---

If it's an 'A' then it also has an intel D865GCL mainboard with AGP.


--- Quote ---Today I pulled out an old Agilent Infiniium MSO8104A.  This DSO is a little newer but much lower end than the Wavemaster, maybe a 1/4 of the price.    It also uses XP-Pro.  It has an Intel Celeron D 3.20GHz  with 256K L2 cache.    Is has the original mechanical drive in it.     It does however come with a 1Gb Ethernet port.   
--- End quote ---

What it also comes with is an Adlink M880 or intel D915GUX PCI Express mainboard (depending on the version of your scope) which both are PCI Express boards.


--- Quote ---I repeated the test on the Wavemaster collecting at 5GS/s, 5M samples.  This requires 531 ms.   
Using the Infiniium collecting at 4GS/s, 8.2M samples required 42 ms.    I was actually running some math on the Infiniium and still out performing the LeCroy.
--- End quote ---

Not surprising when considering that the Agilent has a Gbit NIC which is connected via its's own PCI Express lane so doesn't affect the PCI bus that is used for the Acquisition system.

On the LeCroy the 100Mbps NIC also doesn't use the PCI bus, it's connected via CSA to the chipset.

It shouldn't really come as a surprise that just plugging in a PCI Gbit NIC won't give you the same performance.

The bottom line of all this is that if pulling sampling data out via network is of upmost importance for you then the WM8kA is simply the wrong scope, and plugging in some network card certainly won't change that. LeCroy's strenght lies in its internal processing capabilities, and that's why people buy them, not to be used as simple acquisition system for external processing. And really, if all you need is a sampling system that delivers the data to your PC as fast as possible then bench scopes are generally not a good choice, and you really should have a look at something like a PXI system which is much better for what you're trying to do.


--- Quote ---I tried to run an FFT with the Infiniium and see what it would display at the sample frequency.  They don't seem to allow you to do this.

--- End quote ---

There's a lot of stuff you can't do on the Agilent that you can do on the LeCroy.

Wuerstchenhund:
More Rigol DG1062z Square Wave Tests

Since the previous screenshots gave me eyesore (green on white, yuck!) I thought let's just re-do them. This time around however I not only tested at 1MHz and 25MHz but also at 5MHz, 10MHz, 15MHz and 20MHz.

As before the SA is an Agilent E7495B, the cable a Huber & Suhner Sucoflex 100 (up to 18GHz) and the BNC-to-N adapter a Huber & Suhner rated to 18GHz as well.

The various shots show how the square wave composition deteriorates with increasing frequency. The 1MHz one shows pretty much all the harmonics one expects, but at higher frequency this changes until at 25MHz it's essentially just a two tone signal.

joeqsmith:

--- Quote ---It shouldn't really come as a surprise that just plugging in a PCI Gbit NIC won't give you the same performance.
--- End quote ---

Just to be clear, when I was measuring the dead times of the two DSO's, Ethernet was not used.   I never looked at how fast I could pull data off the Agilent.   


--- Quote ---The bottom line of all this is that if pulling sampling data out via network is of upmost importance for you then the WM8kA is simply the wrong scope, and plugging in some network card certainly won't change that. LeCroy's strenght lies in its internal processing capabilities, and that's why people buy them, not to be used as simple acquisition system for external processing. And really, if all you need is a sampling system that delivers the data to your PC as fast as possible then bench scopes are generally not a good choice, and you really should have a look at something like a PXI system which is much better for what you're trying to do.

--- End quote ---

To be clear, the Wavemasters software and PC are out dated and slow.  What would you expect for a 13 year old PC based instrument.   Using a faster Ethernet card on the PCI bus will improve download performance.     

The high end LeCroys do have some very impressive features when it comes to processing the data.   Even my old 7200 with its 68000 VME chassis has far more features than most low end modern DSOs.   Using these dated high end DSOs for home hobbies has been a blast.   LeCroy does not seem to hold a lot of resale value and as they age, like the old Wavemaster, the prices drop.   

I'm sure there are many reasons why people buy what they buy.   Personally I like seeing some of the old equipment in use and certainly am not going to put people down for how or why they do what they do.    I just enjoy the fact that so many of us enjoy playing with electronics and are willing to share there experiences.   

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