Products > Test Equipment
True analog scopes
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tggzzz:

--- Quote from: tautech on December 24, 2022, 03:35:26 am ---I've pushed the 350 MHz model past 600 MHz and it still triggered and displayed the frequency.

SDS2202X-E is pretty cheap HP at just $620 considering you can open it up to 350 MHz and it will keep you busy discovering all it can do. Hope it likes you.  ;)

--- End quote ---

I've pushed my 350MHz Tek 485 past 1.1GHz, and the triggering was rock stable and the waveform was perfectly displayed albeit reduced in amplitude :)

I only paid £50, but a more usual price would be £200. You couldn't make a business out of selling them, thoigh.
tautech:

--- Quote from: tggzzz on December 24, 2022, 10:17:10 am ---
--- Quote from: tautech on December 24, 2022, 03:35:26 am ---I've pushed the 350 MHz model past 600 MHz and it still triggered and displayed the frequency.

SDS2202X-E is pretty cheap HP at just $620 considering you can open it up to 350 MHz and it will keep you busy discovering all it can do. Hope it likes you.  ;)

--- End quote ---

I've pushed my 350MHz Tek 485 past 1.1GHz, and the triggering was rock stable and the waveform was perfectly displayed albeit reduced in amplitude :)

--- End quote ---
Screenshots required as proof please.

Thanks, needed this push to find the old posts.....with screenshots:
https://www.eevblog.com/forum/testgear/dso-bandwidth-test-sds1104x-e-dsox1102g-to1104-gds1054b/msg2391324/#msg2391324
tggzzz:

--- Quote from: tautech on December 24, 2022, 10:31:43 am ---
--- Quote from: tggzzz on December 24, 2022, 10:17:10 am ---
--- Quote from: tautech on December 24, 2022, 03:35:26 am ---I've pushed the 350 MHz model past 600 MHz and it still triggered and displayed the frequency.

SDS2202X-E is pretty cheap HP at just $620 considering you can open it up to 350 MHz and it will keep you busy discovering all it can do. Hope it likes you.  ;)

--- End quote ---

I've pushed my 350MHz Tek 485 past 1.1GHz, and the triggering was rock stable and the waveform was perfectly displayed albeit reduced in amplitude :)

--- End quote ---
Screenshots required as proof please.

--- End quote ---

I'm away for Christmas, so none are available ATM.

The triggering would have worked at higher frequencies thanks to the tunnel diodes in that part of the circuit. The only reason I couldn't push it further was because the amplitude was reduced to 0.2 div, the min specified for triggering.
MrAl:

--- Quote from: Sherlock Holmes on December 12, 2022, 08:49:59 pm ---Do true analog scopes still get produced? is there a market for them or specialized applications for which a digital scops is not suitable? I suppose too that a true analog scope couldn't really use a digital display unless the resolution of the screen was huge and that in turn implies there'd need to be some kind of A/D conversion involved, so it wouldn't be true analog scope...

--- End quote ---

Analog scopes are better for somethings because they can show the difference between regular noise and noise caused by the circuit sometimes when the noise is very small.  The noise can indicate a problem with the circuit and when it is small it could be the scope so you cant tell if it is the scope or the circuit if using a digital scope sometimes.  An analog scope has a very smooth output unless there is noise so the noise will show up differently, sometimes has just one tiny bump.  If the digital scope naturally has several tiny bumps you cant tell if it is the circuit or the scope.

This can be a problem troubleshooting some power converters such as sine synthesized converters that output a nearly clean sine wave.  When i did some troubleshooting long time ago the rule was no digital scopes even though we could have gotten some more information from using one such as FFT.

These days digital scopes are better than back then, but there will always be that scope noise vs circuit noise issue which may or may not be an issue depending on what kind of circuit you are dealing with.

I prefer a digital scope these days because they are so much smaller and once you get to know them you can do a lot with them.  There may be times when you run into a problem though.

For a very extreme example, try illustrating the Lorentz Force Law:
F = qE + qv × B
using a digital scope. It's impossible because there is no electron beam (ha ha) to be influenced by an electrostatic or magnetic field.
With an analog scope it's simple, fast, and easy.  It's also very direct because there are no intermediate sensors required.
David Hess:

--- Quote from: BillyO on December 22, 2022, 11:01:49 pm ---
--- Quote from: David Hess on December 22, 2022, 10:52:11 pm ---.. they always lack the basic functionality of a true spectrum analyzer, like a noise marker and correction for RBW.  These things would be trivial to add, but for whatever reason DSO designers decline to do so.
--- End quote ---

Well if they did, how would they convince you to buy their spectrum analyzer?
--- End quote ---

Perhaps, but the capabilities and use cases are not the same.  A DSO with these features is more comparable to a low frequency network analyzer.


--- Quote from: baldurn on December 22, 2022, 11:23:10 pm ---
--- Quote from: alm on December 22, 2022, 10:56:57 pm ---Any sweep function generator with any half-way decent scope with a second channel or external trigger input can do it:
--- End quote ---

I can tell you that trick is nothing like the real thing.
--- End quote ---

The usefulness depends a lot on the sweep generator and oscilloscope.  My sweep generator can produce logarithmic sweeps making the display easier to read, and if for instance a Tektronix 2247A or 2236 analog oscilloscope is used, the oscilloscope can place a marker on the screen showing the frequency and separately amplitude at that point.  I have had less success using DSOs like this because they do not make an integrated gated frequency measurement, so their frequency accuracy is more limited.

I think the Tektronix 2465 series with the timer/counter option can work like this also.


--- Quote from: tautech on December 23, 2022, 11:08:13 pm ---You for one know times have changed and the 3 scopes Dave went on to rabbit about having 500uV/div ranges, well most of Siglent's DSO's have that too.
--- End quote ---

The only reason that the 2225 has a 500 microvolt/division range is that its lower bandwidth design is lower noise which allows it, and it is lower noise than the Siglent DSOs without severe bandwidth limiting or averaging.  That is after taking into account how peak-to-peak noise is displayed on an analog oscilloscope.  Dave did not quantitatively measure the noise of the 2225 when he made that video.

I would still prefer the Signlent DSO to the 2225 baring exceptional circumstances.  I use old oscilloscopes because they are the most cost effective for me, but that is not the case for most people.
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