The 100MHz Siglent SDS1104X-E and an upgraded 500MHz Agilent MSO7054A
Very nice compact pulser, as compared to my good old Tektronix 284.
Excelent piece of work Leo !
Has anyone come across any readily available good and cheap SMA(f) - BNC(m) adaptors? (not surplus expensive ones, but cheap when bought new)
The main problem with most of the cheap BNC adaptors and plugs that I've seen is that they are missing the raised flange around the end of the ground connection on the plug, so don't connect well with the socket. The plating on a lot of them does not help much either.
I've sometimes bent the contacts out a little so that they connect better, but that's certainly not ideal.
I use these https://www.digikey.co.uk/products/en?keywords=314-1184-ND when testing the pulsers.
Thanks, but it was more the ones to allow an SMA based pulser to be used on a BNC scope that I was wondering about, and those are the ones that seem harder to do right - however the “You may also be interested in....” bit on the page that you linked to actually led to fairly cheap ones that at least looked OK. I'll need to try some sometime.
I've had so much trouble with cheap connectors that I tend to buy surplus good ones, which are often not too expensive.
One of the good things about the BNC version of the pulser is that it avoids most folk having to mess with these adaptors.
The discussion about the potential effects of BNC to SMA adaptors got me to wondering if I could see any difference with the IBZ DS800C 4GHz scope that I have.
I hadn't used it much before, and don't normally deal with anything this fast, so it was a bit of a learning curve... With the pulser I was finally able to give it a proper workout.
These are connectors that I used and some prices:
An old surplus Huber+Suhner. No idea of the model, but it looks like RS 716-4779, which is £61.69+VAT.
Emerson VA506. It was from ebay, but is £5.43+VAT from CPC
Cinch 29-3855. It was £2.95+VAT from RS
Also from ebay: “Handy Utility Adapter BNC Female Jack To SMA Male Plug RF Connector Straight EW” #401116160491. £0.99 including post from China.
There are probably a few more (or at least larger) variables involved when using this scope than something like a CSA803, so the rise times are a bit of an estimate. I also only tested one sample of each.
Anyway, the numbers that I came up with for now are:
52ps H+S
53-54ps Cinch 29-3855
54-55ps Emerson VA506
58-60ps ebay 99p
The sheet I got with this pulser gave the measured rise time as 31.8ps
Has anyone tried this with something more stable? This is rather pushing the limits of a scope that is $300 new!
Deliberately moving/loosening the connectors did suggest that there was not really much instability caused by this adaptor - although I would still like to get hold of an SMA version, and something a bit better to test it on.
The discussion about the potential effects of BNC to SMA adaptors got me to wondering if I could see any difference with the IBZ DS800C 4GHz scope that I have.
I hadn't used it much before, and don't normally deal with anything this fast, so it was a bit of a learning curve... With the pulser I was finally able to give it a proper workout.
...
...
The sheet I got with this pulser gave the measured rise time as 31.8ps
Has anyone tried this with something more stable? This is rather pushing the limits of a scope that is $300 new!
Deliberately moving/loosening the connectors did suggest that there was not really much instability caused by this adaptor - although I would still like to get hold of an SMA version, and something a bit better to test it on.
Thanks for the comparison. It seems even the cheapies are not too shabby.
Screenshots please! As it is a USB scope it should be easier to do than most of us.
The risetimes indicate much better than 4 GHz bandwidth, probably >10 GHz. If the pulser itself really is 31.8 ps, then your scope manages approximately 41 ps. (rise times of source and scope add as root-sum-of-squares). Even using the more conservative conversion factor of 0.45/Tr, you get ~ 11 GHz estimated bandwidth.
I'd be very interested in seeing the shape of the pulse (overshoot, ringing, etc.).
I had never heard of this USB scope before, but I am very interested now.
Has anyone tried any experiments using this device as a step source for TDR impedance measurements.
I hope I'm doing this right...Tek 2445
Has anyone tried any experiments using this device as a step source for TDR impedance measurements.
For fun i did try sticking on a SMA T adapter and put it on my scope. Worked reasonably well. It could tell if a short 15cm coax was close to 50 Ohm. I could also tell the difference between sticking a SMA terminator on the end of a coax directly versus using adapters to go to BNC to N to SMA before going in a terminator. (I think i just wanted to go to BNC and back but didn't find the correct gender BNC to SMA adapter in a hurry but has some N ones laying on the bench)
from PSPL app note AN3045C:
They use their pulse sharpener to mod the 18 GHz 54754A TDR
to 50 GHz, using a non-TDR 50 GHz 54752A scope plugin. That
means that they must re-implement the coupling to the DUT.
Picosecond Pulse Labs has been bought by TEK, but the app note
is still on the net. The app note is about comparing different TDRs.
The 54750 can use convolution to calculate away its own risetime.
regards, Gerhard
Thanks for the comparison. It seems even the cheapies are not too shabby.
Screenshots please! As it is a USB scope it should be easier to do than most of us.
The risetimes indicate much better than 4 GHz bandwidth, probably >10 GHz. If the pulser itself really is 31.8 ps, then your scope manages approximately 41 ps. (rise times of source and scope add as root-sum-of-squares). Even using the more conservative conversion factor of 0.45/Tr, you get ~ 11 GHz estimated bandwidth.
I'd be very interested in seeing the shape of the pulse (overshoot, ringing, etc.).
I had never heard of this USB scope before, but I am very interested now.
It was interesting how much the speed went with price, but I suppose that shows the effort that went into getting the performance right. Law of diminishing returns there too!
I've attached a couple of plots. I should start another topic sometime for more plots from it, but too many other things I should be doing at the moment...
There have been some threads related to the DS800, like:
https://www.eevblog.com/forum/testgear/10-ghz-usb-oscilloscope-by-darwin-sabanovic/but there's not really that much out there on it.
Leo,
great job done! Thank you.
Next - my small contribution to the knowledge base.
Lecroy LA354 (Iwatsu TS8500).Analog-digital;
Bandwidth - 500 MHz;
The resolution of the scanning CCD-matrix: 800x480 pixels;
Waveform Processing - up to 1000000/sec.
In fact, the measured value of RiseTime = 633 ps.
(this does not differ in channels 1 and 2)
LeCroy WavePro 7300A (release date 2008)The bandwidth is 3 GHz;
Samplerate - 10/20 GSa/s (realtime), 200GSa/s (equivalent mode, RIS)
In fact, the measured (in RIS mode) value of RiseTime:
1 Channel: 139 ps.
2 Channel: 141 ps.
3 Channel: 141 ps.
4 Channel: 133 ps.
The average is: (139+141+141+133) /4=138.5 [ps]
Agilent/HP 54845AThe bandwidth is 1.5 GHz;
Samplerate - 4/8 GSa/s (realtime), 500GSa/s (Equivalent Time)
In fact, the measured (in Equivalent Time mode) value of RiseTime:
1 Channel: 223 ps.
2 Channel: 215 ps.
3 Channel: 217 ps.
4 Channel: 200 ps.
The average is: (223+215+217+200) /4 = 214 [ps]
Agilent DSO81204B in 13GHz enhanced bandwidth mode.
Agilent DSO81204B in 13GHz enhanced bandwidth mode.
The front is formed by only 4 points. I think it was better to use accumulated sampling (equivalent time mode) here.
Here, "Calculated scope risetime" is unrealistically optimistic.
In its new generator modules Leo gets the Rise time ~33ps measured with Tek CSA 803A with SD-26. The SD-26 has its own value of Rise time ~17.5ps (according to the specification). This means that the new module has a Rise time of approximately ~28ps (calculated using formula: Risetime Tsystem
2 = Tscope
2 + Tpulser
2)
But for the calculation you are still using 50ps, which leads to large distortions.
Yes, as I've mentioned before the values "gets out of hand" for the really high bandwidth stuff and as I've also said before there's no way for me to know which version of the pulser the user has and I'm not sure how to handle two different pulser risetimes in the spreadsheet. Say the word and you'll have access to the spreadsheet in order to make it better!
Yes, as I've mentioned before the values "gets out of hand" for the really high bandwidth stuff and as I've also said before there's no way for me to know which version of the pulser the user has and I'm not sure how to handle two different pulser risetimes in the spreadsheet. Say the word and you'll have access to the spreadsheet in order to make it better!
It would be right that anyone who communicates their measurement results should also report the rise time from the passport of the generator Leo that he received.
Thank you, I appreciate your efforts over the table, and no sense that I should interfere in it.
Now that i got my 'new' sampling scope working and calibrated i also gave this fast pulser a test.
This is done on a HP 83480A with a 83483A Electrical sampling module(20GHz bw) and the result is 49.8 ps (10% 90%). For the sake of completeness i also included a measurement with 20% 80% rise time. I couldn't figure out how to get a screenshot off the thing using a floppy so i resorted to oldschool CRT photography.
Test report for my pulser (Serial num 4) shows 49.53ps, so that's surprisingly close.
Welcome to the club! :-)
Above the screen, under STORAGE, the print & setup keys, and their "blue-shifted" versions.
regards, Gerhard
Welcome to the club! :-)
Above the screen, under STORAGE, the print & setup keys, and their "blue-shifted" versions.
regards, Gerhard
Ah thanks, that worked. What i did before was save trough a different method that made a .pix file that i couldn't find a way to open. The TIFF format looks a bit blury but the GIF is perfect and makes for a nice small file size too. Not auto incrementing the screenshot filename is a bit of a pain tho.
Looking at the photo tells me that my CRT calibration might be a bit out of wack tho. The menus look cream colored in the screenshots while they look more like gray on the actual screen. I prefer the gray look anyway so its the least of my worries. A bit more cornering is the timebase calibration trimm cap that seams like it might be on its way out. It was very touchy during the calibration procedure. If i give it a strong enugh wack on the case where the cap is while running i can see some glitching in the waveform.
Now that i got my 'new' sampling scope working and calibrated i also gave this fast pulser a test.
This is done on a HP 83480A with a 83483A Electrical sampling module(20GHz bw) and the result is 49.8 ps (10% 90%)...
Test report for my pulser (Serial num 4) shows 49.53ps, so that's surprisingly close.
If you have close results with the Leo device's passport, then your oscilloscope parameters are close to that of Tek SD-26, which Leo applied. That is something about
~18 ps (HP 83480A with a 83483A).
The own rise time of your generator module is about
46.5 ps (probably this is one of the earlier versions).
Agilent DSO81204B in 13GHz enhanced bandwidth mode.
The front is formed by only 4 points. I think it was better to use accumulated sampling (equivalent time mode) here.
Good call. Here's the results when using ET. It shaves about 8pS off the results.
Good call. Here's the results when using ET. It shaves about 8pS off the results.
Now, for calculations it would be nice to know the rise time from Leo's passport for your generator instance.
Good call. Here's the results when using ET. It shaves about 8pS off the results.
Now, for calculations it would be nice to know the rise time from Leo's passport for your generator instance.
The rise time on this one was recorded at 33.99pS.