Hah! I'm guessing the fine print says you get
200MHz at 50 ohms.Thanks for the pics... I've seen similar- bumpilies... in our fast TEK an thought it was my circuit.
George H. (my rigol is only 50 MHz.)
The DPO2024 doesn't have a 50 ohm mode. I suspect they peaked it (hence the overshoot) to squeeze out a little extra sinewave bandwidth, at the expense of rise time.
I remember when Tek scopes always provided a bit *more* bandwidth than what they guaranteed.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
It was a sad day for me, about a dozen years ago, when I had to explain to a group of Tek factory engineers that a scope lives and dies by its step response. Hallen/Hollister/Traa and Co. would never have made that mistake.
Overshoot seems to have become more or less universal.
Cheers
Phil Hobbs
And quite a bit more when you hack them! The DPO3000 series can be hacked from 100MHz to 500MHz.
And serious ringing on the faster scopes
It's not hard to add digital FIR filtering, especially on a digital scope that saves off-screen samples, so you can window invisibly. Give the users a choice of response, essentially Bessel or Butterworth. Nobody wants ringing, so always fix that.
It's amazing the junk that people are shipping.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Yikes.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
I think John needs an upgraded TDS744A. :)
I've visited John's shop several times, and I can assure you that they have a lot of great toys. :)
When I started out consulting, back in early 2009, that famed librarian and optical fibre guru ecnerwal sold me a very nice HP instrument rack. I put it on some super heavy duty wheels from McMaster-Carr, so I have a great ho me for boat anchors. Without that, they're a pain.
(Lawrence, any time you feel like getting rid of the other one, let me know .)
Cheers
Phil Hobbs
Snap, I bought a couple of these
I put a parts carousel on a drum dolly
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Is that your rack? Because there's definitely an 11xxx series sampling scope in there. SD-24s are going cheap on eBay.
ZPAS doesn't seem to ship to the US, at least not from their eBay site--where did you get them?
I've thought about mounting up two relay racks in tandem, but that would require a lot of metal work.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
It's an 11802, with trigger delay lines instead of two of the sampling head slots. That's the one on my bench.
(but it's much messier nowadays)
I like the older b+w versions. They photograph much better than the shadow-mask color ones.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Oh, I know - like that Lecroy scope with Win7 he's ranted about a few times due to the bugs. ;)
It's probably not so easy - not without increasing total bandwidth (and to be a bit clearer, I'm talking about the "bandwidth" above the nominal
-3dB pt) or increasing noise, or making other assumptions that will, in the "right" circumstances, lead to artifacts.
What exactly? Tek had a 1-GHz scope in the _1970s_ that had a beautiful flat-topped step response, and that was when the vertical amp had to drive the CRT plates and not just some little ADC.
The 11800 series has plugins with beautiful flat pulse tops and a 17-ps rise time.
A percent or two of pulse-top artifacts is the most any proper scope should have. Especially given that with modern ones you can fix it in software, there's no excuse for having crap like that on the pulse tops.
Cheers
Phil Hobbs
Hello! That much worse than a butterworth response!
I had the name of someone at Rigol... (a few years ago, a sales guy I think.) It's a long term solution but you could try contacting them.
George H.
We've been in touch with the local Rigol support folks, but so far they have no comment on step response.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
I'm in complete agreement that the aberrations can and should be far less than what many 'scopes currently deliver. All I'm saying is that taking a scope that has lots of ringing (such as in John's photo) and fixing it with just a bit of DSP is not likely to work without problems.
Consider it this way: ringing is evidence that the higher-order harmonics are likely attenuated - i.e. the rolloff is faster than gaussian. A DSP boost of those frequencies (since there's relatively little energy there) will increase the noise and/or artifacts present at those frequencies. No Free Lunch here.
I can understand the seduction that these companies are falling for. I remember designing a vertical deflection amplifier for Tek, and discovering that I could get a nearly 50% increase in bandwidth (and a much flatter bandpass) if I'd only allow a single time-domain spike of maybe 5+% over the initial design spec. It didn't happen - we stuck to the lower aberration spec. There was (at this same time) a 7700-series scope that you could buy that was similarly optimized for bandwidth instead of clean risetime. It's my understanding that those bandwidth-enhanced mainframes didn't sell very ] well. These days there's a narrow kind of specmanship that is rewarding risetimes and bandwidth and cost, while forgetting about those other annoying specs. -F
I'm in the (Dis)United Kingdom, but I imagine you're spoiled for choice for similar type racks in the US. Shelves in racks are definitely the way to go for this sort of use.
Yes, it's a picture of one of my racks and it's an 11802 (my favourite of that sampling family).
Unfortunately the days where it was cost efficient to buy kit in the US and ship to the EU are long past, with the demise of surface shipping.
To be honest I regret investing so much in the TeK plugin's and mainframes. I have three faulty mainframes in the corner of my office and these things are pretty much impossible to repair - I'll be looking at going the HP route when this 11802 unit finally slips it's anchor.
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?It's
ing
ing specs.
Yup, I remember that one--that's the one they tried to sell me, and I reall y reamed them out about the overshoot. I wound up buying a TDS 7704A demo u nit instead. It still overshot a bit, but not like the other one!
Roger on not putting a huge boost on signals where there's not much SNR, bu t even then you could at least average away the ringy noise.
I routinely use microwave transistors at baseband, so analogue bandwidth sh ouldn't be such a huge issue, I'd have thought.
I interviewed with Thor Hallen back in 1987. Unfortunately Tek's revenue pe r employee was never that great, so they didn't pay well. I made more money as a postdoc at IBM than Tek was offering for a more-than-entry-level perm anent slot.
Cheers
Phil Hobbs
I'll miss my 11802 when it finally dies. I wish I knew someone who could repair them. Tek never published the schematics.
I must have a quarter million dollars (at original purchase price) worth of SD-series heads in my cubby. One of them is good to 50 GHz.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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