A possibly dumb Q on digital oscilloscopes - Page 1
Forum section: electronics / testgear

author: peter-h
author_rank: Super Contributor
timestamp: July 06, 2017, 10:59:30 am
content: I have been in the analog sphere since the 1960s... up to a 400MHz Tek scope (long thread here about repairing that one, which I finally managed with some great help).Now looking at a DSO... I did read the long thread on the RTB2000.Now... a Q on some basics:If you want to capture a single shot waveform at say 300MHz then (per Nyquist) you need to sample at 600MHz, and even then the result will be a lot worse than an analog "300MHz" scope which is perhaps -6db at 300MHz. Most DSOs sample faster e.g. the "300MHz" RTB2000 samples at 1.25Gsps, the (more pricey) HP DSOX3034T samples at 5Gsps. So all of these should deliver a good rendition of a 300MHz sinewave for example.But why such oversampling? The 5Gsps scope should be marketable as "2.5GHz"The next Q is on how these things work on periodic waveforms.Let's say you have a signal which repeats 1000 times. Now, if you have a precise S&H circuit, you could sample each cycle of that signal at 1000 different points along the cycle. If the signal was 300MHz then each cycle would be 3.3ns but since you have 1000 looks at it, your A-D conversion time needs to be 3.3us which is trivial. So, with periodic signals, you could get amazingly good sampling and waveform rendition. You could have 12-bit or 14-bit vertical precision...And getting 1000 looks at it is actually incredibly pessimistic because with a 300MHz signal you will get 300 million looks at it in just one second, which is about the time it takes you to move your head from looking at the PCB to looking at the scope.Admittedly knocking up a S&H with picosecond precision is not trivial but it also isn't that hard. The time resolution (the tiny x increment) is easy enough to do, I would think. It's a lot easier than building a 12-bit A-D with a 200ps conversion time...Does any DSO do this, or do they all treat everything as single-shot?Let's face it - most signals are periodic otherwise nobody would have ever bought an analog scope

author: coppice
author_rank: Super Contributor
timestamp: July 06, 2017, 11:12:13 am
content: Quote from: peter-h on July 06, 2017, 10:59:30 amLet's face it - most interesting signals for hard to diagnose problems are one off transient events. That's why storage scopes were in demand, despite their eye watering prices; people used a lot of Polaroid film in their scope cameras, despite hating the stuff; and even the earliest very limited digital scopes were an instant hit for those with an adequate budget.

author: JPortici
author_rank: Super Contributor
timestamp: July 06, 2017, 11:23:15 am
content: good luck debugging a serial bus using Equivalent time sampling. That's good to look at the eye diagrams / pulse shapes but not much more.But they do still make scopes with very high analog bandwidth and much lower samplerate just for this purposemaybe ( ? ) if you keep sending the same message but how often are you going to do that?a fast storage oscilloscope, with high enough sample rate to have a gentle rolloff to mantain a decent square wave at high frequency will make your life much easier.a modern DSO will also let you do something useful with the data besides basic measurements

author: RoGeorge
author_rank: Super Contributor
timestamp: July 06, 2017, 11:26:11 am
content: Q1: It's a 300MHz scope because the analog front end linear bandwidth is from 0 to 300MHz. You can see a frequency higher then 300MHz, but there is no guarantee for its correct amplitude.Q2: Yes, there are digital oscilloscopes for repetitive signals, with max freq. for probes + analog front end much higher then 2 * the sampling frequency. Tektronix is calling them Digital Sampling Oscilloscope (for repetitive signals), as oposed to Digital Storage Oscilloscope (for non repetitive signals):http://www.tek.com/document/online/primer/xyzs-scopes/ch2/oscilloscope-typesAlso, many digital scopes have a software option for high resolution (oversampling), so, for example, an 8 bit ADC is used to produce a 10 bit waveform on the scope's display.

author: capt bullshot
author_rank: Super Contributor
timestamp: July 06, 2017, 11:30:27 am
content: The thing you describe (1000 repetitions of sampling ...) is called "equivalent time sampling" or "repetitive signal mode" on a typical DSO. It requires precision timing circuits and high analog bandwith, but moderate sample rates that can be lower than the signal frequency (there were some old DSOs spec'd with some 100MHz BW and 20MS/s).It's basically the same way analog sampling scopes work. Not all DSOs can do that, I believe most of the entry level ones today cannot.For a single shot capture, as a rule of thumb, you want 10 times the sampling rate of the signal frequency (so 100MHz scope should have at least 1GS/s for useful single shot results). This is because there's no signal reconstruction filter on the digital side of the ADC (which would be required to satisfy Mr. Nyquist)Many simpler DSOs today work in single shot capture mode with an internal repetition rate of some 1k to 100k "waveforms per second" rate. This means, each time the sampling memory is filled (one single acquisition is triggered), one waveform is acquired. Then an overlay of all these waveforms is output on the display.Those simple scopes cannot trigger at the precision timing required for ETS (equivalent time sampling), so the resolution in time domain isn't increased. Better scopes do, they can give you a quite detailed picture of the signal at multiples of the real time sampling rate.

author: peter-h
author_rank: Super Contributor
timestamp: July 06, 2017, 11:33:24 am
content: OK; let me ask a Q: is this repetitive signal sampling method available in most DSOs?Looking at the RTB2000, it doesn't look like it could be any worse than a DSO costing 2x more, when it comes to displaying the signal.The other day we had a lot of trouble getting a TI A-D converter to work reliably, SPI interface driven from an ARM processor, and it turned out to be a bit of ringing on the clock signal. A 60MHz DSO showed absolutely nothing but a 100MHz analog showed it perfectly. This is an example of a periodic waveform which you want to see in as much detail as possible.I have no quibble with the reasons for single shot support, of course.

author: capt bullshot
author_rank: Super Contributor
timestamp: July 06, 2017, 11:40:07 am
content: Repetitive sampling / ETS is a feature of "better" DSOs.Don't expect any entry level DSO to support it.The minimum "ns/div" setting gives you a hint if the scope supports it, with ETS this goes way much faster than without, say 5ns/div for a simple sampling 100MHz / 1GS/s DSO compared to 100ps/div for a 1 GHz / 4GS/s DSO with ETS up to some 100GS/s

author: tggzzz
author_rank: Super Contributor
timestamp: July 06, 2017, 11:45:30 am
content: Those aren't dumb questions, they are perceptive questions. To hint at a few answers...Not all storage scopes are digital; I have one and access to another. They are a pain to use compared to digitising scopes; for single-shot waveforms digitising scopes are usually preferable.There is a strong argument that for digital signals, you should use a scope to assure signal integrity, and then flip to tools that work in the analogue domain (e.g. logic analysers, printf statements etc). That strategy greatly reduces the need for digitising scopes, but does not eliminate it.To understand oversampling you need to understand DSP.Verybriefly, oversampling simplifies the implementation of front-end filters and reduces the aliasing associated with signals that exceed the Nyquist bandwidth. Oversampling can also help reduce white noise and increase effective vertical resolution.You have to be careful about what bandwidth you are thinking about when invoking Nyquist. If you have an audio signal on a 10MHz carrier, to recover the audio signal youdon'thave to sample at >20MS/s; 44kS/s is sufficient. But the front-end bandwidth (including sampler) still needs to be >10MHz. I have a sweet commercial Tek scope with ~30kS/s which is used to see 140ps risetimes. Occasionally you see them on fleabay at high prices; currently one is (claimed to be) available for ~£1000!

author: macboy
author_rank: Super Contributor
timestamp: July 06, 2017, 01:57:09 pm
content: These are very good questions. The fact that you understand enough to ask these questions, means that they are in fact smart questions.To display a sine wave only, then you can invoke Nyquist, sample at merely >=2x the signal frequency, apply a "perfect" reconstruction filter on the samples in memory, and display a smooth waveform at a high resolution. But real signals aren't just sine waves, and we can never ensure that the scope is receiving absolutely zero signal at all frequencies above the Nyquist frequency. A higher sampling frequency will always allow greater signal fidelity on-screen, especially when displaying samples directly, without a reconstruction filter (no interpolating, etc.).I have an old (>30 year old) digital sampling scope that has a 200 MHz bandwidth, but only 250 MS/s maximum real-time sampling speed. For repetitive signals, it does repetitive sampling to build up the waveform from many cycles. The maximum "equivalent time" sampling rate is 10 GS/s. This gives very good fidelity for steps or pulses (such as clocks). At that sampling speed, it captures only 2 or 3 samples per trigger, and it can take 5 to 10 seconds to build up a complete set of samples. If you want to use averaging to reduce noise, then you can imagine that it will take a minute or more to get a good display.My much newer (but >15 year old) 2 GHz scope has a 16 GS/s sampling rate. It also has a 50 GS/s maximum equivalent time sampling rate for repetitive signals. Given the high sampling speed, this is not usually necessary, but when using multiple channels, the sampling rate is divided among them (e.g. "only" 4 GS/s at four channels), so the repetitive mode becomes more and more desirable.Many low bandwidth entry level scopes (say, 50 MHz to 200 MHz) use 1 GS/s ADCs which are an off-the-shelf commodity these days, so they have no inherent need for high speed repetitive sampling. Higher end models will still add this as a feature.

author: peter-h
author_rank: Super Contributor
timestamp: July 06, 2017, 03:00:09 pm
content: Many thanks all.Yes I well recall the analog storage scopes. They implemented it with a special CRT. I built some simple scopes in the 1970s - 20MHz sort of thing and using uA733 op-amps and some fast bipolars to drive the deflection platesI last used a 10x8cm PDA tube from Mullard.Which DSOs offer ETS? It does sound like that is more or less essential for seeing waveform detail comparable to a 400MHz analog scope. It probably also explains why the RTB2000 is so much cheaper than say an "HP" MSOX3034T which costs about £8k (and that's before you hack the 70MHz model to do 300MHz which I seem to recall is possible). OTOH if the HP can do single shot at 5Gsps that may well do it anyway. But 8k is way too much for me. I could stretch to 3-4k.I have another DSO Q:Taking the fairly common "4 analog plus 16 digital" model, doesn't that make a logic analyser largely redundant? I have a 16-channel IWATSU SL-4602 from the 1980s. It's pretty good for looking at slow logic signals but it doesn't even stuff like serial data decoding which some of these scopes offer as options. Maybe the devil is in the detail in that e.g. the IWATSU box came with some very nice probes which will always be expensive to make.

author: tggzzz
author_rank: Super Contributor
timestamp: July 06, 2017, 04:04:22 pm
content: Quote from: peter-h on July 06, 2017, 03:00:09 pmYes, repeat no.If you have an analogue signal (which they all are unless they are photon-counting or femtoamp), then a receiver is making a decision as to whether an input voltage represents a 0 or 1. If you have two receivers (e.g. one in a scope), thenthere is the chance that they will makedifferentdecisions. Trivial examples include different voltage thresholds and sampling times.all the more so the higher up the "information stack" you go. Extreme examples of the latter are frequently found in comms systems, where the input signal can be completely buried in noise, and/or the 0/1 decision is a probability collapsed by a Viterbi/trellis decoder.That leads to the conclusion that it is safer to allow your "real" circuit to make the 0/1 decision, and to look at its output with, say, a logic analyser. However, that is not always possible (if you can't probe the specific signal), and it is not always necessary (especially for some slow speed stuff like UART signals).Sometimes the choice depends on how easily and effectively the probes can be attached. LA probes can be cheaper and smaller, and have less impact on the UUT.Other times the choice depends on the triggering condition. Scopes are OK for simple "linear" triggers, but LAs can excel with complex historical state-based triggers such as "the fourth memory access after the read from IO port 0x1234".

author: peter-h
author_rank: Super Contributor
timestamp: July 07, 2017, 02:10:06 pm
content: Could someone please give me a pointer on which digital scopes, starting from the bottom e.g. the RTB2000, have ETS?

author: nctnico
author_rank: Super Contributor
timestamp: July 07, 2017, 03:17:17 pm
content: Quote from: peter-h on July 07, 2017, 02:10:06 pmI'm not clear on why you insist on having ETS? It is only useful for repetitive signals. As long as the samplerate is at least 2.5 times the bandwidth then a single shot acquisition will give you the same information.

author: alm
author_rank: Super Contributor
timestamp: July 07, 2017, 03:35:36 pm
content: Why not try one of the scopes you are considering side by side with your analog scope? I find it hard to believe that you require ETS. Keep in mind that a digital scope will display signals differently anyhow (e.g.more emphasis on noise).It is the designers job to match the sampling rate to the analog front-end. With a perfect brick wall filter, any sampling rate over two times the filter bandwidth is sufficient. With a traditional Gaussian response that was also used with analog scopes, a higher sampling rate of maybe 4-10x the front-end bandwidth is required because of the slow roll-off. Quite a lot of signal beyond the -3 dB point will still end up at the ADC. And for something that is closer to a brick wall filter, a sampling frequency of 2.5x the filter bandwidth might suffice. Seethis Keysight appnotefor more details about different filter types.If the designer did their job well, than there should be very little frequency content that makes it through the input filter that is beyond the Nyquist frequency. So any improvement through equivalent time sampling should be quite minimal. Though I am sure there are some signals with edge rates far beyond the rated bandwidth that would show a large difference with a higher sampling rate.

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: July 07, 2017, 10:12:35 pm
content: These app notes might be interesting for you regarding your sample rate question. Ultimately, oversampling doesn't hurt, and having some buffer helps avoid real-world issues like aliasing.Oscilloscope Sample Rate vs. Sampling Fidelity - the first part about Nyquist theory might clear some things up.http://literature.cdn.keysight.com/litweb/pdf/5989-5732EN.pdfThere's also this "What Oscilloscope Bandwidth do I need?" style app note that has some good theory:http://literature.cdn.keysight.com/litweb/pdf/5989-5733EN.pdfThe 1 GHz+ Keysight oscilloscopes have an equivalent time mode that give you an equivalent of 128 GSa/s.There are also "sampling oscilloscopes" that have dedicated hardware for this instead of software implementation, you can learn more about that on our blog:https://community.keysight.com/community/keysight-blogs/oscilloscopes/blog/2017/02/22/real-time-or-sampling-oscilloscope-key-comparisons

author: peter-h
author_rank: Super Contributor
timestamp: July 08, 2017, 06:29:06 am
content: Those video tutorials on digital v. analog scopes are brilliant! I did learn a lot there.Unfortunately there is no practical way for me to borrow a digital scope to compare.It looks like the RTB2000 will do the job nicely. It does have all the right features of the much more expensive scopes; I guess they kept it "cheap" by using the slower sampling rate for which there are relatively low cost ADCs.I need to check out whether there is a bandwidth hacks which still work on current models because I really want the 4 channel + digital version and that is very pricey at 300MHzI did check Ebay etc for used older model scopes but they aren't a whole lot cheaper.

author: nctnico
author_rank: Super Contributor
timestamp: July 08, 2017, 08:45:48 am
content: There is another problem with the RTB2000 you are overlooking: for 300MHz bandwidth to be usefull you will need 50 Ohm inputs and the RTB2000 doesn't have these. You'll need different probes / probing techniques like connecting signals directly as well. Regular high impedance probes will load signals over 100MHz too much due to the probe capacitance at the tip so you never get a good view of a signal even if the probe says it has a 500MHz bandwidth.

author: peter-h
author_rank: Super Contributor
timestamp: July 08, 2017, 10:38:02 am
content: OK; a good point.I used to use an active probe which had a 50 ohm output to a 50 ohm scope. Pricey...However a 50 ohm input may not be quite mandatory. In a previous life I used to have some very pricey Tek passive probes which had a much lower capacitance than the standard "300MHz" ones. I remember taking a (broken) one apart. They used a very special cable, with a thinner than a hair single conductor. I have not seen such probes since. It was grey, quite fat, and came with a spring-loaded ground tip for use on PCBs with a ground plane. A google/images doesn't find it though.EDIT: P6009https://www.recycledgoods.com/tektronix-passive-probe-with-013-0071-00-screw-on-tip-p6009/OTOH can't one use an active probe with a non-50-ohm scope input?Maybe I should look at used scopes. This is taking the thread off topic however. I must have 4 channels, the ability to see lots of detail on 50MHz signals, and the 8 or 16 channel digital mode would be really nice, especially if one can read off serial data on a clock+data wire pair (e.g. SPI kind of thing). What is the best scope around the $3k-4k area, from a few years ago? Obviously active probes would be extra...

author: tautech
author_rank: Super Contributor
timestamp: July 08, 2017, 10:50:21 am
content: Quote from: peter-h on July 06, 2017, 10:59:30 amWhy wouldn't a SDS2304X do all you want ?300 MHz, 4 analogue channels, 16ch MSO, 2 Gsa/s, 140 Mpts ,140,000 wfm/s

author: nctnico
author_rank: Super Contributor
timestamp: July 08, 2017, 11:08:34 am
content: Quote from: peter-h on July 08, 2017, 10:38:02 amLook at the GW Instek MSO2000 series. No 50 Ohm inputs and 200MHz bandwidth but for the rest it ticks all your boxes at less than $2k. I have the version without digital channels of this oscilloscope (GDS2204E) and it works very well as a scope for daily use. I used to have an Agilent MSO7104A but the GW Instek GDS2204E is easier to drive for daily use and way less noisy (signal noise that is).You can use 50 Ohm terminators to connect a 50 Ohm (active) probe to a 1M Ohm input but expect some errors in the waveforms at high frequencies.

author: tggzzz
author_rank: Super Contributor
timestamp: July 08, 2017, 11:47:56 am
content: Quote from: nctnico on July 08, 2017, 08:45:48 amJust so. But it is always worth reminding people of "low impedance" "Z0" "resistive divider" probes.They are rugged, and you can make yourself - unlike "conventional" passive *10 probes. Input capacitance is <1pF and input resistance is 500ohms or 1000ohms - which is usefully better than "high" impedance passive *10 probes.They aren't differential, but there are techniques to make a passive differential probe which doesn't go down to DC. I haven't tried them, so I can't comment on their effectiveness; FFI seehttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

author: David Hess
author_rank: Super Contributor
timestamp: July 09, 2017, 03:05:12 am
content: Quote from: peter-h on July 08, 2017, 10:38:02 amThe P6009 is a somewhat specialized x100 high impedance passive probe. All such x100 probes have a lower input capacitance than their x10 counterparts simply because of their higher division ratio but they are also normally not much faster than 100 MHz.You might be thinking of the unusual Tektronix P6048 x10 probe which is designed to operate with a standard high impedance 1 megohm input while providing a 1 kilohm and less than 1 picofarad at the probe tip. This probe is essentially a low impedance probe in disguise with a low impedance termination at the oscilloscope end. Its bandwidth is primarily limited by the oscilloscope bandwidth and input capacitance so with some oscilloscopes, it could reach 200 MHz or more. My guess is that ultimately it was limited to about half the bandwidth of the fastest high impedance probes or 250 MHz but it had an input impedance better than both high impedance probes and some low impedance probes.Probe bandwidth is specified assuming the 25 ohm source termination which is almost reasonable for a high speed logic source so while high impedance passive probes are worse than a low impedance probe above about 25 MHz (10 picofarads and 500 ohms), with a low source impedance they can still be acceptable to 300 MHz and maybe somewhat higher. Short connections or even better a coaxial connection are required for good results.QuoteSure, an external 50 ohm feedthrough termination can be used at the 1 megohm oscilloscope input to terminate the active probe. Tektronix at one point even made a 500 MHz active probe which had a switchable termination built in.Quote from: peter-h on July 07, 2017, 02:10:06 pmManufacturers tend to avoid advertising this because it casts their less expensive real time DSOs in a poor light. If you want to know, then you need to study the specifications carefully.Better these days is to evaluate the performance based on real time sample rate like it is better to consider transition time rather than bandwidth. As long as the transition time of the oscilloscope is faster than the transition time of the logic, then it will produce accurate measurements. The sample rate just needs to support the transition time and even cheap DSOs can manage this.Tektronix has argued that averaging is as good as equivalent time sampling but I am dubious because you cannot average triggers and it requires multiple acquisitions anyway.

author: peter-h
author_rank: Super Contributor
timestamp: July 10, 2017, 09:37:49 am
content: I looked at the SDS2304X.Does anyone think that an 8 bit ADC is significantly worse compared to say the 10 bit one of the RTB2000?I have a low-end DSO which is 8 bit (TDS2004B) and one can clearly see the steps on that. But more to the point I suspect it makes fourier analysis a lot worse because the dynamic range is poor. A spectrum displayed with a log y axis is a likely to be a bit of joke when the data came from an 8 bit ADC.

author: nctnico
author_rank: Super Contributor
timestamp: July 10, 2017, 10:15:13 am
content: Quote from: peter-h on July 10, 2017, 09:37:49 amIf you want to take a serious look at a frequency spectrum you need a spectrum analyser. Still this doesn't mean FFT on a DSO is useless as long as it is very deep (1Mpts) so you can have a very high frequency resolution. I have used FFT quite a lot for a recent project involving analog and digital signal processing.

author: peter-h
author_rank: Super Contributor
timestamp: July 10, 2017, 01:38:54 pm
content: The Rigol DS4034https://www.rigol-uk.co.uk/Rigol-DS4034-Digital-Oscilloscope-p/ds4034.htmlooks like it ticks all the boxes. They are bundling various software options e.g. serial decoding. OTOH some reports here of Rigol are quite negative.Are these Chinese scopes of reasonable quality, mechanically (quality of switches etc)?Some of their products appear identical to some Tektronix ones.Unfortunately I really struggle to see the difference between these various Chinese scopes e.g. the above Rigol and the Siglent SDS2304X which is much cheaper.Then I read this forum and see so many reports of functions in all of these scopes which simply don't work. Plus reports of poor response (e.g. slow cursor movement) which the Tek and Keysight scopes do properly.It would be easy for a nice digital scope user to buy one of these and after a year discover that some feature (e.g. SPI decoding) doesn't work and then it's out of warranty.For example right now we are running a 22-bit A-D with an ARM processor and the SPI is running in 24-bit mode where 3 bytes get transferred. It would be great if the scope could decode the 24 bits of data into an integer.Plenty of threads about most of these scopes being unable to decode serial data which is off-screen which I agree is almost totally useless. One exception is Instek, apparently.

author: nctnico
author_rank: Super Contributor
timestamp: July 10, 2017, 03:45:36 pm
content: Personally I avoid oscilloscopes from Owon, Hantek, Rigol and Siglent. Too much hit&run strategies going on. That doesn't mean all Asian companies are like that. MicSig and GW Instek for example make true on the promised features.

author: peter-h
author_rank: Super Contributor
timestamp: July 10, 2017, 05:17:44 pm
content: Having just spent a few hours reading EEVBLOG I am homing in on the GW INSTEK GDS-2304A.The only other candidate is the R&S scope which costs about 2x as much.Neither comes with bundled-anything and no special offers I can see.I guess the two are very similar except that the Instek is 8-bit and the R&S is 10-bit. I do need SPI decoding for 8 16 and 24 bit packets and it has to work properly.

author: JPortici
author_rank: Super Contributor
timestamp: July 10, 2017, 05:22:14 pm
content: GDS-2000A and E (and MSOs) have free decoders, you just have to download them from the website (no idea why they are not included in the first pace)but apparently the 2000A can only decode on the LA channels??Quote

author: peter-h
author_rank: Super Contributor
timestamp: July 10, 2017, 06:39:40 pm
content: That presumably avoids a user interface item for setting the signal threshold on the analog traces...

author: tautech
author_rank: Super Contributor
timestamp: July 10, 2017, 09:16:23 pm
content: Quote from: peter-h on July 10, 2017, 01:38:54 pmEncoders seem to be the most questioned but it's mostly if the manufacturer used detented ones or not. If the encoder algorithm has been poorly implemented then a detented version is the workaround that many resort to.Before replacement was common a knob swap using a larger knob for better feel was often used.QuoteThen you need to keep looking, not take only just the opinions of a minority few that have some axe to grind.QuoteRemember that yesterdays deficiencies that have made it into print have mostly been addressed in firmware revisions by most brands. Check a manufacturers firmware page for the history and frequency of FW updates to get some good idea how mature the product might be.QuoteAll features on the SDS2304X work as expected. The warranty is 3 years.QuoteManufacturers implement feature in different ways and not all implementations suit everybody. Does it mean you can't get in info/measurement you need...........no it doesn't.For an overview:All the rest you need to know about how Siglent's display Decoding is in this post:https://www.eevblog.com/forum/testgear/choosing-200-300mhz-4-channel-logic-and-canlin-analyser-budget-$2000-$2600/msg1156185/#msg1156185

author: peter-h
author_rank: Super Contributor
timestamp: July 10, 2017, 09:22:19 pm
content: Many thanks.Are there any scopes which can decode 24-bit SPI into a 24-bit integer?

author: nctnico
author_rank: Super Contributor
timestamp: July 10, 2017, 09:42:45 pm
content: GW Instek GDS2000E series (and presumably the derived MSO2000 series) can decode SPI from 4 to 32 bits (number of bits freely selectable) and it doesn't decode only what is on screen but the entire memory.

author: peter-h
author_rank: Super Contributor
timestamp: July 11, 2017, 10:47:27 am
content: That's really useful - many thanks.Are there some "old" HP (Agilent/Keysight) scopes which tick these boxes and which are worth searching for on the used market? These would be very pricey today if you want logic inputs and serial data decoding. However I have used a lot of HP gear over the decades and it is really well built and mostly works very nicely.A couple of years ago I bought a Marconi 2024 signal generator and an Anritsu 2661G for 2k the lot. This is perfectly usable stuff, if rather old now. OTOH if any of this stuff breaks it can easily be uneconomical or impossible to repair, so you need to get it cheap.

author: tggzzz
author_rank: Super Contributor
timestamp: July 11, 2017, 11:19:29 am
content: Quote from: peter-h on July 11, 2017, 10:47:27 amBe aware that digitising scopes have been improving rapidly over the past couple of decades. Digitising scopes from a decade or two ago mostly have some significant gotchas for some applications. Hence the specfor each individual type of scopehas to be read and the consequences understood!Principal specs to be aware of include the analogue front-end bandwidth, the single-shot and real-time sampling rates, the depth of the memory buffer, sharing a single ADC between all used inputs, whether post-processing is on the whole memory buffer or just what's visible on the screen, ADC resolution.

author: peter-h
author_rank: Super Contributor
timestamp: July 11, 2017, 12:00:17 pm
content: Thanks.One thing which is missing on older stuff is the amount of buffering - because memory used to be expensive and you need very fast RAM for a logic analyser / digital scope type of application (even if you interleave it). But does one need megabytes of memory in reality? What applications need it?ISTM that everything out there is 8-bit, except the RTB2000 which is 10-bit but samples at "only" 1.25Gsps.

author: nctnico
author_rank: Super Contributor
timestamp: July 11, 2017, 12:22:28 pm
content: Quote from: peter-h on July 11, 2017, 12:00:17 pmAll! It is much easier to capture a trace at a long time/div & high samplerate and zoom in to get more detail without needing to setup complicated trigger settings to catch part of a signal with a higher samplerate (let alone reproduce a rare event). Even better if the oscilloscope has a search function where you can search for anomalies.

author: David Hess
author_rank: Super Contributor
timestamp: July 11, 2017, 02:11:10 pm
content: Quote from: nctnico on July 11, 2017, 12:22:28 pmI disagree with this in some respects. Delayed acquisition capability (delayed sweep) is just as good except where one needs to zoom into the pretrigger record (1) or where only a single acquisition is available. Searching for anomalies is a job for DPO mode rather than a search function; DPO operation will always catch it but how can you know what an automated search missed?Long record lengths for zooming replaced delayed acquisition when increasing integration made them a cheaper solution. Increasing integration also made implementing automated searches of long processing records less expensive than DPO operation.(1) There actually is a way to implement delayed acquisition with negative time but it was never an important enough feature to bother implementing in a DSO. Some analog sampling oscilloscopes did it to avoid having to use a delay line or pretrigger signal.

author: peter-h
author_rank: Super Contributor
timestamp: July 11, 2017, 02:17:21 pm
content: I have an opportunity to get an ex demo (half price) HP MSOX3034T. It is not clear if this has the 16ch MSO option (SPI etc decoding) but otherwise looks very good.Are there any known gotchas?

author: nctnico
author_rank: Super Contributor
timestamp: July 11, 2017, 02:26:49 pm
content: Quote from: David Hess on July 11, 2017, 02:11:10 pmDPO mode cannot catch an anomaly 100% because it has blind time (including the operator); only a properly set trigger condition can but that is a different discussion. Search works best in stop mode; it isn't a realtime tool so you can change the search parameters and examine the same data again. When combined with decoding or FFT you can also search for specific messages, data or frequency peaks.Quote from: peter-h on July 11, 2017, 02:17:21 pmMake sure it includes the MSO probe or expect to spend $300 to $400 on the probe. Also check for the options. Dunno if this model can be hacked and/or if you are willing to do that.

author: borjam
author_rank: Unknown
timestamp: July 11, 2017, 02:44:04 pm
content: Even with their (many!) limitations I wouldn't just discard Chinese oscilloscopes. Honestly, it makes me feel bad to have a Rigol and read those fantastic application notes from Keysight, Tektronix, etc.An example of how useful (or not) the infamous DS1000Z can be.Last week a friend was struggling with a simple communications problem: reading information from a device using Modbus. When he asked for help all he could say was "the reading function returns a timeout".How do you debug that? Of course there are two manufacturers involved and they will probably say "my stuff is fine". So you grab the cheap DS1000Z, make a capture, and you find out all this (warning, not rocket science, pretty obvious!)- The command is properly sent and understood by the other device. It actually replies. Also, it replied in 25 ms.- There is a bug in the Modbus library of the device sending the request, it doesn't set the RS485 interface in receive mode after transmitting.- We better add termination, although the signal is useful better to avoid that ugly overshot (the decoded screenshots were taken after we fitted a couple of resistors)- And we could even decode a couple of packets in order to check that it really works according to the documentation.With all the deficiencies, "pluses" and a somewhat provincial software design with subpar interface responsiveness, and surely it helps that this is not exactly rocket science (Modbus at 9600 bps over a 50 m twisted pair), I would say that the 450 euros of the oscilloscope have been more than worthy.While we would have found out sooner or later, the toy really allowed us to find out pretty soon. Moreover, you can always make a better case with the manufacturer when you can document your findings.I know there are much better oscilloscopes which are much more expensive. I now that the math functions in my old LeCroy 9400 are much better designed. But what was the price of a 9400 back when it was launched?

author: peter-h
author_rank: Super Contributor
timestamp: July 11, 2017, 02:57:58 pm
content: This is somewhat off-topic but I do a lot of Modbus stuff and one could have found your issue with any DSO, no matter how cheap or slow. In fact one could have done it with an analog scope, if one could retransmit the Master request over and over.Being able to decode NRZ (RS232/422/485) data would save a fair bit of time...The 25ms response delay is common; I have seen up to 1 second if doing a block request. The main reason is that the people who develop the software in many Modbus slave devices are using C++ and "if in doubt use a float" and "if your code is so crappy that you are getting underflow then use a double"and right away you are looking at several ms just for a division, if using some cheap CPU.FWIW, I have a good selection of old HP and Tek kit (back to 1980s) and it is outstanding. I have the service manuals and have repaired some of it. It's clear to me that DSOs are however in a different category, with vastly more complexity and close to zero repairability once something nontrivial goes. That's why ex demo stuff is probably worth looking at. That MSOX3034T lists at about 8k GBP - not sure what the digital input situation is; they all seem to have the front panel header... would they just ship them without the probe??

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: July 11, 2017, 03:58:07 pm
content: Quote from: peter-h on July 11, 2017, 02:57:58 pmYes, on the InfiniiVision oscilloscopes that support digital channels (2000 X-Series and up), we do ship DSOs with a populated MSO board, and users can upgrade their DSO to an MSO - they get a license and cables.Also, repair on new equipment (especially digital scopes) is a whole new monster compared to older analog scopes.Finally, we do offer UART decoding (RS232, RS422, RS485) on the 2000 X-Series and up scopes:http://www.keysight.com/en/pd-1951451-pn-DSOX3COMP/computer-serial-triggering-and-analysis-rs232-uart-for-infiniivision-3000-x-series?cc=US&lc=engplus some user definable manchester & NRZ trigger and decode:http://www.keysight.com/en/pd-2796492-pn-DSOXT3NRZ/user-definable-manchester-and-nrz-trigger-and-decode-for-3000t-x-series-oscilloscopes?nid=-32976.1210574&cc=RO&lc=eng

author: peter-h
author_rank: Super Contributor
timestamp: July 11, 2017, 04:18:42 pm
content: Thanks Daniel.The option being mentioned to me is DSOXT3APPBNDL which apparently enables absolutely everything. Does this make sense?Google seems to suggest it does enable everything.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 11, 2017, 05:24:43 pm
content: Quote from: nctnico on July 11, 2017, 02:26:49 pmThis, and it is only really good for repetitive signals.QuoteThat depends on the scope. Most of the time I search for anomalies I use the scope's analysis tools (like WaveScan or InfiniiScan) in running mode, and that's much more convenient that having to manually go through acquire-stop-search cycles. Also, capturing the timing of glitches over an extended period (I just leave it running and when I come back the scope shows me a list of events with timestamps) often helps a lot to find the source.

author: peter-h
author_rank: Super Contributor
timestamp: July 13, 2017, 11:20:51 am
content: Unfortunately the used MSOX3034T which was on offer has gone, so I am in the market for one, with the digital inputs, and SPI and NRZ (RS232 etc) serial decoding. The ARINC429 decode option would be nice too... Upper limit GBP 4k which I believe is about right for an ex rental (good condition) scope - roughly 1/2 of the new price.I don't mind if it comes from the USA (I have a DHL account number etc) but then it would need to come from some reputable source.Rental companies do very well out of equipment sales because they buy the stuff at distributor prices and get a LOT of money on the rental. In a previous life I used to rent test equipment and you paid the new price in 1 year.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 13, 2017, 11:48:00 am
content: Quote from: peter-h on July 13, 2017, 11:20:51 amThere should be plenty of options. If you can live without ARINC then I'd have a look at the LeCroy WaveSurfer 3000. It's a competitor to the DSOX/MSOX3000T but cheaper and offers a bigger screen, more memory (10Mpts vs 4Mpts), better FFT and a wider choice of probes. For Europe LeCroy has currently a some promos where you get all options or MSO for free:http://teledynelecroy.com/europe/promotions/promotions.aspxI'd also ask about ex-demo units which are regularly discounted by 40% or more.You should be able to get a WS3034 with options within your budget.QuoteTrue, but just because these companies made a killing through rental fees doesn't mean they necessarily sell of their kit for reasonable prices.

author: peter-h
author_rank: Super Contributor
timestamp: July 13, 2017, 01:36:48 pm
content: A WS3034 does look nice; I have emailed them. These are not so commonly seen so I wonder how buggy they are...?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 13, 2017, 02:07:48 pm
content: Quote from: peter-h on July 13, 2017, 01:36:48 pmI haven't seen any bugs in the current software, there have been a few minor bugs in the initial software version when they came out in 2014 but nothing that would have stopped you working on what you were doing, and they were fixed pretty quickly. LeCroy is a big-name A-brand like Keysight, Tektronix and R&S, and offers very good software support for its scopes. They also generally support their scopes much longer than other manufacturers.At work we have quite a few of the WS3054 (500MHz variant) and no problems aside from one arriving DOA (was immediately replaced by LeCroy). We don't have any DSOX3k scopes but we have several DSOX/MSOX4104A scopes, but most of our engineers seem to prefer the WS3054 when needing a 500MHz scope (of course if they need more than 500MHz BW in a compact scope then they have little choice). The larger sample memory is one thing (also, the 4Mpts in the DSOX/MSOX halves or quarters depending on what you do, which can leave very little memory available). The WS3000 uses the same UI (MAUI, which was developed for touch interaction from the start) as LeCroy's high end scopes, and they can use the same ProBus active probes (Keysight artificially limits compatibility between probes for Infiniivision like the DSOX3k/4k and Infiniium scopes, which are their highend scopes). And it comes with WaveScan (a tool to find glitches in signals, works even in real-time) and LabNotebook (for documenting measurements).A few of these scopes are also used on the road (i.e. carried around site to site) and so far the WS3k seems to do very well.I believe there are a few people in this forum who bought a WS3000 scope, might be worth asking them about their satisfaction with the scope.

author: JPortici
author_rank: Super Contributor
timestamp: July 13, 2017, 06:11:00 pm
content: Quote from: Wuerstchenhund on July 13, 2017, 11:48:00 amholy... why do they send me just marketing crap on emails?thanks for pointing that out, tomorrow i'm definetly making the boss see that link. exactly one week ago we were talking about getting new equipmentold video but gives a hint at what wavescan is, on the WK3000

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 13, 2017, 06:31:43 pm
content: Quote from: JPortici on July 13, 2017, 06:11:00 pmThey're not very good at marketing, most of the people that work in sales are engineers. On the upside, they never sank to the level of those silly "ours-vs-theirs" comparativewhitepapersmarketing pamphlets that especially Keysight and Tek love so much.QuoteKeep the link if you want to see in the future what current promos are there for Europe, the promos change but the link doesn't.QuoteYes, that's a good video. It shows pretty well how the scope operates.As you said the video is a bit older, so for anyone watching this be aware that the scope in KF5OBS' video is one that ran on one of the initial software versions back then in 2014. Back then there was no DVM (which came with a later software version and was a free "upgrade" for any WS3k), fewer serial decode standards and the optional AWG was just a signal generator (as DVM, AWG functionality was included in a later firmware, being a free upgrade for anyone who had a WS3k with signal generator option). Since then, besides fixing bugs, the updates brought new functions and other improvements.

author: tautech
author_rank: Super Contributor
timestamp: July 13, 2017, 08:20:36 pm
content: Quote from: peter-h on July 13, 2017, 01:36:48 pmThese have been in the field for a few years now but only as LeCroy's in western markets where Siglent whom make them have an agreement that they can only sell the OEM in China as SDS3000 models.A search for SDS3000 in the forum gives plenty of hits for you to study up on.I had ideas of getting one for myself but Siglent are bound by their agreement and can't even supply me.The relatively small memory depth by todays standard is a small negative but otherwise they are a nice scope.There's a pic of a Siglent one at their reception here:https://www.eevblog.com/forum/testgear/siglent's-new-products-sds3000-series-oscilloscopes/msg558936/#msg558936

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 14, 2017, 06:43:04 am
content: Quote from: tautech on July 13, 2017, 08:20:36 pmYes, Siglent manufactures the hardware (which is a co-development between LeCroy and Siglent). The software is made by and maintaned by LeCroy, though. Which I think is a great thing as Siglent has proven that they can make very good hardware at low costs, and the area where they struggle most (software) is out of their hands.QuoteWell, even if you were able to get one, unless you're good in Chinese language it'll probably not of much use because as far as I know the Siglent variant of the software comes with Chinese language onlyQuoteThe sample memory is only small when compared to Rigol and Siglent scopes which have more memory but little means of making use of it (primitive manual search function at best, nothing like WaveScan), and for serial decode they only decode what's on the screen.What I like on the WS3000/SDS3k is that it can use pretty much all of LeCroy's ProBus active probes including old ones made in the '90s because (like the big LeCroy scopes) uses their unified X-Stream software (although the WS3k is X-Stream Lite). That makes for a wide choice of probes, new and used, much more so than for any comparable other scope.

author: peter-h
author_rank: Super Contributor
timestamp: July 14, 2017, 11:19:55 am
content: I have emailed all the LeCroy emails but they are not responding. The UK one came back saying "I am on maternity leave till September - please email xxxx"Their UK and German numbers herehttp://teledynelecroy.com/europe/promotions/promotions.aspxare dead.I am still keeping an eye out for the Keysight one because it does ARINC429 decoding which is something I am starting to be involved it and having a protocol analyser for it is really handy. They do exist but then you get yet another expensive box which gets used maybe once a year...

author: JPortici
author_rank: Super Contributor
timestamp: July 14, 2017, 12:33:36 pm
content: try to contact the sales office athttp://teledynelecroy.com/support/contact/instead

author: peter-h
author_rank: Super Contributor
timestamp: July 14, 2017, 01:29:16 pm
content: Yes, the phone +41 22 719 2111 is dead and no reply to the email addressIs there a working email/phone for Europe?+44-1582-433280 works...

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 14, 2017, 01:31:05 pm
content: Quote from: peter-h on July 14, 2017, 11:19:55 amLeCroy Europe recently went together with Anritsu Europe (bot companies are still separate, but they combined their sales offices in Europe) so some of the numbers have changed. Try JPortici's link instead.QuoteWell, if ARINC429 decode is critical then yes, the only options in this class are the Keysight DSOX/MSOX3kT and the Tektronix MDO3k (and you don't want the Tek because it's painfully slow and comes with a truly horrible UI). LeCroy only offers ARINC 429 decoding in the WaveSurfer 10 and higher scopes.The Keysight DSOX/MSOX3kT is a good general purpose scope (although it comes with a hefty premium). Just remember, when looking at sample memory, Keysight's already small 4Mpts get 1/2'd or 1/4'd depending on what you do, how many channels you use and if you use the LA part.At the end of the day, only you can decide which features have more weight for you. But when comparing don't forget to include probes in your calculation. You can spend a lot of money on probes.

author: peter-h
author_rank: Super Contributor
timestamp: July 14, 2017, 01:40:41 pm
content: ARINC429 uses manchester encoding. It may be possible to decode that with one of the options on the LeCroy scope. 1553 uses manchester also. OK; you won't get the 429 label etc extracted and presented but that doesn't matter. OTOH it is trivial to knock up a manchester decoder and feed that into a logic channel.These scopes all come with four standard probes.It's interesting to look at stuff like active probes, especially what appears on Ebay. The $1000 HP one (< 1pF) pops up on Ebay for 1/2 price but this is a lot less likely on LeCroy. OTOH the LC one is cheaper to start with. I think one of these probes is worth having for when you are chasing dodgy clock signals.Of course "HP" stuff is overpriced...

author: peter-h
author_rank: Super Contributor
timestamp: July 14, 2017, 06:35:29 pm
content: The WS3034 is rather outside my budget too, even after the discount, with the various optionsThe Q is whether all these are worth getting.The problem is that LeCroy apply these special discounts to an inflated price e.g. $5500 here for the basic boxhttp://www.tequipment.net/lecroy/oscilloscopes/digital-oscilloscopes/$5500 = £4200i.e. they inflated the price by 30% or so to start with.

author: nctnico
author_rank: Super Contributor
timestamp: July 14, 2017, 07:23:06 pm
content: Also note how the options add nearly 50% to the price.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 14, 2017, 07:31:11 pm
content: Quote from: peter-h on July 14, 2017, 01:40:41 pmNot really. Not one of the active probes I bought was more than $250. I got an AP033 (500MHz differential), AP034 (1GHz differential), HPF1500 (1.5GHz active) and HFP2500 (2.5GHz active), the former two were less than $150 each (they have a weak point in the plastic housing which is cheap to fix), the latter two a bit more expensive. BTW, all these probes work fine even on the WS3000.I also often buy used probes for work, at similar prices. If you can be a bit patient then there are lots of good deals out there.The reason HPAK (HP/Agilent/Keysight) probes are so expensive is because there are more HPAK scopes out there, which is because when it's about scopes many people only know HPAK and Tek and only very few know LeCroy. Which means there's a lot more demand for HPAK gear on ebay which keeps prices up.And this is in addition to a smaller selection of available HPAK probes for the MSOX/DSOX.QuoteAnd if it really carries the "HP" label it's also at least 19 years old.Quote from: peter-h on July 14, 2017, 06:35:29 pmNo, because paying for the decode options would be silly (you can get them for free).The built-in AWGs are rarely worth the money, no matter which scope brand. The same or even less money gets you a much better standalone AWG.QuoteWell, this is for a brand new scope from a US distributor. The listed base prices are list prices. Which, just to give you some perspective, is $8648 for the DSOX3034T. Or£6698 from one of the cheaper UK distributors.However, test equipment prices aren't fixed, list prices are merely a rough guideline and can be haggled down like nothing. Even with little effort you should be able to get the options included for free, LeCroy has been doing this pretty much since they came out with the scope in 2014 (only the lazy ones pay list prices). There's also the option of asking for a demo scope, which usually comes with all the options, is maybe 1 or 2 years old, comes with all accessories in the original box and a full manufacturer warranty usually for some 40% less.Or you can just go to a distributors web page and pay the list price minus any little incentive they offer there (if any).BTW, the same is equally true for Keysight.

author: nctnico
author_rank: Super Contributor
timestamp: July 14, 2017, 08:30:33 pm
content: If you buy a lot of equipment then there is some leverage for volume discounts. I couldn't get a single cent of a Wavesurfer 3000 and the local distributor offered a Rigol scope instead when I said the WS3000 was too expensiveAre they friggin' kidding me? I think the local distributor lost a potential customer for good!

author: jpb
author_rank: Super Contributor
timestamp: July 14, 2017, 08:53:16 pm
content: On the subject of ETS, the WaveJet (I have a WaveJet 334) has ETS at 100GS/s which works well on repetitive signals.I think that ETS is disappearing from a lot of scopes because the triggering has changed from analogue (with a time dilation circuit) to digital interpolation and the ETS principle doesn't really work on digital interpolation (the sample points don't move around in the same way to sample at different intermediate time values).

author: peter-h
author_rank: Super Contributor
timestamp: July 14, 2017, 09:33:00 pm
content: I have told the Le Croy UK guy that he is just inflating the prices massively.In the meantime I have been told that the US disti is prohibited by Le Croy from shipping to the UK - to protect the distributors here... obviously this can be easily sorted via a contact in the USA, but then the warranty would be difficult. And any return to the USA is $200-300 for the round trip, anyway.I will keep looking. £4k is the budget for 4+16 and serial analysis

author: nctnico
author_rank: Super Contributor
timestamp: July 14, 2017, 09:40:07 pm
content: Quote from: peter-h on July 14, 2017, 09:33:00 pmDid you already take a close look at the GW Instek MSO2000 series?

author: tautech
author_rank: Super Contributor
timestamp: July 14, 2017, 09:53:23 pm
content: Quote from: peter-h on July 14, 2017, 09:33:00 pmShame you might have burnt bridges.QuoteHmmm, SDS2304X = 1667.64 + MSO HW & SW, so probably ~2K BP plus taxes.(Promo pricing)

author: David Hess
author_rank: Super Contributor
timestamp: July 14, 2017, 11:58:25 pm
content: Quote from: jpb on July 14, 2017, 08:53:16 pmThe sample points are still asynchronous to the input signal (1) but the interpolated trigger point may suffer from aliasing. Centroid time to digital converters work this way but they low pass filter the pulse edge to reduce aliasing and create a consistent signal. In a DSO with digital triggering, there are different waveforms which will produce the same trigger point with aliasing or the same waveform can produce different trigger points with aliasing so the aliasing corrupts the trigger.Tektronix argues in their application notes that the difference between ETS and averaging with a digital trigger is insignificant.(1) Or at least they better be. HP made some DSOs which deliberately dithered the sample clock and then compensated for it in order to prevent synchronizing between the input signal and the sample clock which would cause ETS to fail. Frequencies counters face the same problem so high performance ones dither their clock.

author: peter-h
author_rank: Super Contributor
timestamp: July 15, 2017, 06:06:08 am
content: "Shame you might have burnt bridges"Not sure how else you can tell somebody that the price is way too highI did look at the Instek and it costs a lot less but I would rather spend 4k on something with the extra features.Looking around US sites, I see Le Croy stuff with various promotions but with the 3034 always listed at $5500. Here is another onehttp://www.saelig.com/product/wavesurfer-3034.htmwhich is bundling the 500MHz update, which is worth a great deal. I didn't realise the 500MHz was another software upgradeNo wonder these people are all banned from selling to Europe!This is another good routehttp://www.saelig.com/teledyne-lecroy-wavesurfer-3000/wavesurfer-3024.htmA 3024 with a 350MHz upgrade!

author: tautech
author_rank: Super Contributor
timestamp: July 15, 2017, 07:30:31 am
content: If you end up sourcing from Saelig there's a EEVblog member discount thread here:https://www.eevblog.com/forum/testgear/equipment-discounts-from-saelig/

author: peter-h
author_rank: Super Contributor
timestamp: July 15, 2017, 07:48:51 am
content: I doubt anyone in the USA can ship to Europe. Tequipment are explicitly prohibited.

author: JPortici
author_rank: Super Contributor
timestamp: July 15, 2017, 08:30:56 am
content: pardon me but i don't get how they would quote you thisQuotewhile they stateQuote from:http://teledynelecroy.com/europe/promotions/promotions.aspxto me including means for free.

author: nctnico
author_rank: Super Contributor
timestamp: July 15, 2017, 08:32:02 am
content: You have to realise that the WS3000 doesn't have peak detect which can be a serious problem when looking at signal where you can't use the maximum sampling frequency. Aliasing can cause all kinds of 'funny' signals to show up or narrow pulses to disapear. This is the sole reason I decided not to buy the WS3000.

author: peter-h
author_rank: Super Contributor
timestamp: July 15, 2017, 04:38:54 pm
content: Does anyone know anything about vendors not honouring warranty in Europe, on stuff bought in the USA? Keysight or LeCroy?It must have come up, because US prices are so much lower.

author: nctnico
author_rank: Super Contributor
timestamp: July 15, 2017, 04:57:01 pm
content: Quote from: peter-h on July 15, 2017, 04:38:54 pmYou have to factor in shipping and import charges as well. Also some stuff just can't be bought because local dealers just don't bother to make sales happen. I'd look around in Europe to find a different dealer. Perhaps a good deal can be had from a used equipment dealer.

author: peter-h
author_rank: Super Contributor
timestamp: July 15, 2017, 05:01:10 pm
content: Import duty is of the order of 5%. There is VAT but you have to pay that anyway (20% in the UK). Shipping on a 5kg box is about $100 so not much.I am looking for ex demo but there is not much about right now, an some Keysight stuff I was was ~7k when the new price is 10k so pointless.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 15, 2017, 09:21:38 pm
content: Quote from: nctnico on July 14, 2017, 08:30:33 pmI remember, but then LeCroy doesn't have an office in the Netherlands so you're pretty much left with local distributors which certainly isn't great and doesn't give you all the opportunities you can get in a country where there's a manufacturer office.But really you don't have to buy lots of gear to get good discounts. Easy to get even for one-off purchases.Quote from: tautech on July 14, 2017, 09:53:23 pmI guess you're right, accusing the trading partner to just inflate prices isn't a sane negotiating strategy.Never forget, vendors usually want to work with you to close a deal, but you have to give them reasons why the price needs to be lower or the offer needs to be better. It's a give and take.Quote from: peter-h on July 14, 2017, 09:33:00 pmYes, that's true. It's pretty much standard for any big brand T&M vendor.QuoteWarranty is not a problem. All LeCroy scopes carry international warranty. Many of our US bought scopes have been serviced in Europe and vice versa. Not an issue with either Keysight or LeCroy (or Tek, or R&S). You just send it to the nearest service point.Quote from: nctnico on July 15, 2017, 08:32:02 amFrom what I understand the requirement of Peak Detect is pretty much down to your way of working. I can't remember when the last time was when I used PD for any serious measurement, it's probably more than 15 years now.But yes, if you really need/want PD then the WS3000 isn't for you (or any LeCroy scope after the old 9384, which I think was the only one which had PD).

author: AR
author_rank: Contributor
timestamp: July 15, 2017, 09:35:28 pm
content: Hello WHI have been doing a preliminary reading of the Lecroy MAUI interface manual, and they have a feature called Analog Compare which allows you to trigger on certain events occurring in the waveformI get the impression that it can be setup to do peak detect type triggering. or am I not understanding something.

author: nctnico
author_rank: Super Contributor
timestamp: July 15, 2017, 09:45:38 pm
content: Quote from: AR on July 15, 2017, 09:35:28 pmThat is not peak-detect. Peak detect produces the minimum and maximum during a sample interval. This is especially usefull when the oscilloscope is working at a low samplerate. Without peak-detect you will miss narrow pulses or they turn up randomly. The same goes for aliasing when the input signal has a higher frequency than the samplerate. In short: with peak-detect you get more meaningfull data on your screen. I always have peak-detect switched on. Practical example: look at a slow process like charging a battery where you likely want to use a timebase of 100s/div or longer but you still want to see if there are problems like the current control circuit oscillating at a high frequency or the battery switching to a different charging mode. Here peak-detect will paint a full picture while normal sampling mode won't.

author: tggzzz
author_rank: Super Contributor
timestamp: July 15, 2017, 10:22:08 pm
content: Quote from: Wuerstchenhund on July 15, 2017, 09:21:38 pmIf you are looking for low duty-cycle digital signals, peak detect is pretty much required.A standard common use-case for that is if you have a microprocessor (or FPGA) blip an output to show that something has happened. That can easily be 1us in 1ms, or worse.

author: peter-h
author_rank: Super Contributor
timestamp: July 16, 2017, 03:25:26 am
content: Why can't one simply trigger from such a pin?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 16, 2017, 07:17:15 am
content: Quote from: AR on July 15, 2017, 09:35:28 pmAs nctnico says this isn't Peak Detect.On a modern scope, the max(!) sample rate is usually more than high enough to avoid aliasing. However, the sample rate also depends on your available memory and your timebase setting, i.e. on the WS3000 which comes with 10Mpts per Ch, the memory is enough to capture up to 2.5ms at 4GSa/s. That means if the period you want to capture is longer than 2.5ms, the sample rate has to drop (i.e. to 2GSa/s for up to 5ms, or 1GSa/s for up to 10ms, and so on). With a drop in sample rate, the usable scope BW (which, according to Nyquist-Shannon, is < 2x fsample) drops as well. For example, if you sample with 1GSa/s your usable BW will drop down to around 400MHz. Now if your scope is the 200MHz model then this might not be a problem as the real analog BW of the front end will very likely be lower than 400MHz, but if not then that means frequency components over 400Mhz will not be filtered out and get into the sampling system, which will cause aliasing (distortion of the waveform). Also, at lower sample rate, as other said you will generally miss very short events (i.e. the high frequency components) like glitches.PD is a (one!) way around that. As nctnico says, PD means the scope samples at full sample rate but only takes the minimum and the max value over a sampling period that's appropriate for the long timebase setting. Because the sampling occurs at full sample rate, aliasing doesn't become a problem, and the acquisition system can still "see" high frequency components it would have missed in normal sampling mode with a much slower sample rate. PD does have its disadvantages, for example while it allows you to see high frequency events, because it only takes the max and min of a sampling period means the waveform on the screen might not be representative of the real signal. It will also look more noisy than it really is. Also, because PD is a sampling mode, the sample memory contains only the Extrema and not the real sample data, which means the data is pretty useless for any measurements (and you have to re-acquire in normal mode to get any measure-worthy data, which doesn't help in one-off events).There's a very good paper on Peak Detect from HP:http://www.hpl.hp.com/hpjournal/97apr/apr97a4.pdfIt's a bit dated (and scope BWs, sample rates, memory sizes and performance has progressed notably since then) but what it says remains still valid. PD was an important tool when scopes came with very low memory sizes (sometimes as low as 1000 points). Modern scopes which offer large memory have alleviated the problem to some extend, but if you want to look at high frequencies over a long period of time then even the large memories of modern scopes aren't enough to capture at sufficient sample rate.Now, on a LeCroy scope, there is no PD. On a modern LeCroy X-Stream scope like the WS3000 you just use WaveScan and let it search for anomalies. WaveScan is a signal analysis tool where you can set certain criteria it should be looking for, and decide what it should do when it finds something (i.e. stop acquisition, take a screenshot, record it in an event tabel, perform specific measurements etc). You can run the scope at full sample rate and have WaveScan search for any anomaly in realtime (you can also use it to search post-acquisition if you want to). And because WaveScan maintains the full sample data and not just the Extrema you'll also maintain a representative waveform.Keysight has a similar tool (although not as flexible) calledInfiniiScanfor their Windows-based high end scopes (Infiniium Series).The advantage of PD is that it requires very little processing power while WaveScan is pretty processing intensive, so it's simple to implement.LeCroy stopped offering PD, after offering in I think only two scopes (9374 and 9384) in the late 90's when processing became fast enough to use alternatives like advanced digital triggers and math, mainly because PD is an acquisition mode which stores altered data (the sample memory only contains the extrema, not the real sample data). On a LeCroy scope, the sample memory always contains unaltered acquisition data) which is part of their design philosophy. Older LeCroy scopes (non-Windows/non-X-Stream) offered advanced triggering and math to capture issues, which on the older scopes sometimes was a bit complex to setup but when done properly worked really well.As to WaveScan, there are some differences on its capabilities between LeCroy's mid-range (WaveSurfer, HDO Series) and high-end (WaveRunner, WavePro, WaveMaster, LabMaster) scopes., but even the variant in the WS3000 can already do quite a lot of pretty useful things (i.e. scanning for shifts in frequency, which in a repetitive signal is an indicator of the presence of some anomaly). It's a really versatile tool.As I said, I haven't used PD in nearly two decades, and before that only on a few occasions, simply because there were always better (to me) alternatives available like triggers and math, even on HPAK scopes. And that includes stuff like waiting for a fast low d.c. pulse on a FPGA output (tggzzz's example), all without PD. It's probably down to what you're used to, i.e. if you used PD often back in the old days of low memory scopes then you might be more likely to still use it. But it's no longer the only option.

author: tggzzz
author_rank: Super Contributor
timestamp: July 16, 2017, 07:54:16 am
content: Quote from: peter-h on July 16, 2017, 03:25:26 am[... a low duty cycle pin...]Sometimes that is sufficient, sometimes not; it all depends on themeaningof the blip.It is more difficult if the frequency or timing relative to another signal is important, of if you are using something else as the trigger.If you have peak detect then you can insert temporary software testpoints likeCode://enter FSM state foooutput(foo, 1)output(foo, 0)...//enter FSM state bazoutput(baz, 1)output(baz, 0)...//enter FSM state baroutput(bar, 1)output(bar, 0)If you don't then you have to find ways of "extending" the pulse, e.g.Code://enter FSM state foooutput(baz, 0)output(bar, 0)output(foo, 1)...//enter FSM state bazoutput(foo, 0)output(bar, 0)output(baz, 1)...//enter FSM state baroutput(foo, 0)output(baz, 0)output(bar, 1)which is completely do-able but more error-prone and tedious, especially as the number of states grows.With imagination there are often ways around problems, but having peak detect is pretty important.With analogue scopes on long duration timebases, you instantly get a feel for what you are missing by the amount of "fuzz" on the signal. Peak detect is the digitising equivalent version of that. Without peak detect it is like having bandwidth limit which changes as the timebase changes.

author: JPortici
author_rank: Super Contributor
timestamp: July 16, 2017, 07:55:38 am
content: Quote from: peter-h on July 16, 2017, 03:25:26 amseeing an event is only useful if you can see the context, context being what is happening in the surrounding pico/nano/micro/milli-secondsthen, imagine you had no peak detect (oh, this i see many times, esp. on rigol) and you trigger from pin.you see that the waveform has updated. WTF? i see no glitches, but it's there. you can't see it because the screen data is an interpolated and decimated copy of sampled data so you see a flat line, but expand it and a sudden glitch appears!as far as i understand you can implement peak detect on lecroy's wavescan, but since it operates on sampled data it may reduce wfm/s (someone correct me please) and will be pointless at lower samplerate

author: tggzzz
author_rank: Super Contributor
timestamp: July 16, 2017, 08:00:21 am
content: Quote from: Wuerstchenhund on July 16, 2017, 07:17:15 amThere are indeed often ways around not havingsomeform of peak detect. But it is very convenient when "randomly" probing to see what the hell is happening, and to warn you that you might be missing an important high frequency effect.Certainly for cheap digitising scopes, "high frequency" means "shorter than one pixel width on the display" - whatever the timebase / memory depth / sampling rate. I don't know how modern high end scopes get around that.

author: nctnico
author_rank: Super Contributor
timestamp: July 16, 2017, 08:03:53 am
content: Quote from: JPortici on July 16, 2017, 07:55:38 amWavescan uses the CPU to do some kind of automated mask testing. It can be convenient but it has blind time and it seems you end up with a whole bunch of snapshots which may not paint a complete picture. Roll-mode + peak detect doesn't have blind time and you capture everything.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 16, 2017, 08:08:29 am
content: Quote from: JPortici on July 16, 2017, 07:55:38 amTrue. But pretty much any decent modern scopes can be setup to capture specific periods before and after a trigger occurs.QuoteBut that is because the primitive toolsets on a Rigol scope, not because it's difficult to setup.QuoteThat's wrong. As stated above PD does not implement PD (i.e. reducing sample data to Extrema). It processes the raw sample data in realtime. The screen refresh rate will drop notably in WaveScan but because this isn't a 'user-staring-on-screen-to-wait-for-glitch-appearing' kind of mode this usually isn't a problem.Quote from: nctnico on July 16, 2017, 08:03:53 amThat's wrong. PD is *not* mask testing, it's a realtime analyzer that looks at specific signal parameters that are user-configurable. It works on repetitive and non-repetitive signals (try that with mask testing), and can do a lot more than just taking screenshots (which is just one option amongst many, i.e. it can also take automatic measurements, record what is happening on other channels, list events with time stamp in a history table, etc, including combinations of actions). It can also give you a second trace which shows a zoomed in of the last detection, i.e. the last glitch that occurred, and so on.Quote from: tggzzz on July 16, 2017, 08:00:21 amYou can find out the same with advanced triggers on pretty much any decent mid-range or high-end scope. No problem. You don't even need WaveScan.QuoteBut we're not talking about cheap scopes. The WaveSurfer 3000 is a lower mid-range scope, and the Keysight MSOX is pretty much in the same category.

author: JPortici
author_rank: Super Contributor
timestamp: July 16, 2017, 08:47:35 am
content: Quote from: Wuerstchenhund on July 16, 2017, 08:08:29 amI can confirm that i only use peak detect on a tek scope- not modern by any standards even if it is still in production- 2.5 kpts, no indicaton of samplerate on screenQuotethe same happens in my lecroy mainframe, which is understandable given its > 20 years oldi found out while troubleshooting a faulty plugin, i would get unexplainable triggers but if i expanded the waveform i would see a literal drop to bottom screen (a failed memory chip) that wasn't there while seeing the full acquisitionQuotethanks for the corrections, but may i ask: what if the event happens during the blind time? (pros and cons of everything of course. no system is perfect)

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 16, 2017, 10:08:40 am
content: Quote from: JPortici on July 16, 2017, 08:47:35 amAs you said, this old scope (7200/7400 Series) is from the late 80's, and back then processing was slow. Also, the 7xxx Series was never meant to be an analysis scope (that was the 9400), it's focus was on the modularity.QuoteAs WaveScan is normally sitting on top of a normal acquisition cycle it will be affected from the scope's own blindtime. PD is also affected by blind time but because it works with reduced data (Extrema vs real sampling data) it takes longer to fill the sample memory and thus the scope will capture a longer period.I'm not saying PD can't be useful (it certainly can) but there's more than one road leading to Rome. Also, the question is what do I want to achieve. If I want to just see if there are any high frequency components then PD is great, but if you see glitches then you usually still have to go back, acquire normally and perform your measurements/analysis (which you can't do on a PD acquisition). If it was a one-off (or a very rare glitch) this isn't much help. Also, quite often you don't want to see what happens when there's no glitch and everything is working normally, you want to see what happens when the glitch appears, and here I think PD is lacking because while it allows you to record long periods of time where everything is OK it provides very limited information when there's an unexpected event.PD is also a mode that is user-centric, i.e. it requires the user to see and identify the problem (and that the user did actually sees the event and not miss it). It's a bit similar to looking for glitches in repetitive signals through persistence mode. Most better scopes have long been offering better alternatives which leave detection of issues to the scope (which in general does it more reliably), but in my experience especially people who learned scoping on analog or simple digital scopes (where pretty much everything is left to user interpretation) rarely make use of these advanced toolsets as they fall back into (in this case outdated) trained behavior.For me, I find it easier to setup appropriate advanced triggers or tools like math and WaveScan/InfiniiScan and leave the scope running for a while, and when I come back I'm not only presented with an indication of the presence or absence of an anomaly, but if there are I also get a list with number of events and the timing, snapshots of what happened on other related channels, certain measurements and so on. Which means I can often right dive into finding the source of the problem. Most of the time I have a good idea how the signal is supposed to look like, so I'm not interested in my scope recording long sessions of when nothing happens.

author: bson
author_rank: Unknown
timestamp: July 16, 2017, 08:50:06 pm
content: Quote from: peter-h on July 13, 2017, 01:36:48 pmI'm only aware of a few trivial bugs in the current firmware. One is that even if you don't have a mouse plugged in it sometimes leaves a cursor on the screen (which goes away at the next touch).Axis labels sometimes aren't shown; disabling and reenabling them makes them reappear for a while.Measurements and decodes do add to blind time. The DVM is a measurement and also adds to it. It can get a bit slow on long records. I'm not sure how the DVM differs from just a plain rms measurement... but I never use it. I wouldn't (and didn't) pay for the toy function gen.In general it's a really nice, though somewhat basic scope. Some minor shortcomings:- I wish it could use an external frequency standard, but it has no timebase input- Mask creation is very rudimentary- I wish it had more flexibility in how to partition the screen and place traces, like side-by-side and resizable traces instead of a simple top to bottom stack with fixed sizes- A couple more math functions would be nice, like four instead of twoBut, in general for my needs it's the cat's pajamas and I'm very happy with it.

author: bson
author_rank: Unknown
timestamp: July 16, 2017, 09:35:12 pm
content: Quote from: Wuerstchenhund on July 13, 2017, 02:07:48 pmAnd if you're not made of money it's nice that a lot of the older active probes available inexpensively on eBay will work fine. The ONLY gotcha I've found is with the AP020 (1GHz, 1Mohm, 1.6pF, 10V range) and AP022 (2.5GHz, 100kohm, 0.6pF, 10V range) where if measurements or the DVM are enabled the trace will flicker once during the blind time or when itretriggersrearms the trigger. But they're recognized and otherwise work perfectly. The differential AP034 (1GHz, 1.5pF, with 10:1 +/-4V, 1:1 +/-0.4V, and AC coupling) works fine, as does of course the current ZS1000 active probe. (I have all those four.) With the ADPPS power supply (50ohm BNC out) they can all be used with other instruments like counters, VNAs, and SAs. Want to see the see the spectrum of a differential 250MHz signal? No problem! (I'd also recommend a really good AC coupler since they won't be auto-zeroed without a ProBus scope.)I asked LeCroy about the flicker and was told the WS3000 is only compatible with probes rated for its bandwidth, which according to them excludes 1GHz and 2.5GHz probes. (But then they sell the ZS1000 as being compatible.) This is a little specious to me, but not worth fussing over - basically they work but are unsupported with no compatibility guarantee. Here's the specific response I got FWIW, which suggests that unless the bandwidth of the probe exactly matches that of the scope (invalidating your probes if you upgrade the bandwidth? can't use them between scopes of different bandwidth?) you're flying on dead reckoning, without no expectation of compatibility unless the probe is explicitly listed in the marketing collateral.QuoteThis was in response to me asking:Quote

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 17, 2017, 07:46:39 am
content: Quote from: bson on July 16, 2017, 09:35:12 pmThe ADPPS is nice but unfortunately it's pretty rare and usually very expensive.The reason all these probes are compatible is because all LeCroy X-Stream scopes use the same unified software. There are essentially only three software packages, one for the current upper mid-range and high-end scopes (64bit Windows), one for the older X-Stream scopes (32bit XP) and one for the embedded scope (X-Stream Lite) which is the WS3000 (32bit Win7Emb). All packages share the same codebase and thus all scopes "know" the same probes. And as the code is updated even older scopes now start to support new probes (e.g. the ZS1000 which is a new probe that can even be used on a 15 year old WavePro 7k).At the moment I'm hunting for some active probes for my Keysight Infiniium DSO8064A scope and I wish the situation were as good as on the LeCroy side, but the choice of active probes that works with this scope is pretty small and these probes (even old ones which still carry the HP logo) often go for a lot of money.In this light the cost of an ADPPS for my LeCroy probes starts to look a lot betterQuoteWhich I think is understandable, some probes are now over 20 years old and have been out of support for a long time, so I don't think it's reasonable to expect them to test for and resolve issues around such old probes.The ZS1000 has been tested because the Siglent variant (SDS3000) is sold with 1GHz BW while LeCroy only offers the WS3000 up to 750MHz (the 1Ghz BW is covered by the WaveSurfer 10).

author: peter-h
author_rank: Super Contributor
timestamp: July 17, 2017, 09:51:29 am
content: Why isn't one active probe same as any other?I realise they need to be powered somehow, via contacts next to the BNC or whatever coaxial connector, but if you are feeding a 50 ohm scope input why is there a compatibility issue?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 17, 2017, 10:02:06 am
content: Quote from: peter-h on July 17, 2017, 09:51:29 amBecause there's a bit more involved than just providing some power. For example, differential probes should be zeroed - this is often done via the scope interface so the scope must be able to identify and control the probe. The scope then can also read out and apply any correction factors that might be required, and set the scale to represent the correct voltage levels.Also, each manufacturer has its own idea how the physical probe interface should look like, not just for technical reasons but also to prevent you from using competitors' active probes (although LeCroy offers an adapter to allow some Tek probes to be used with a LeCroy scope).There are some generic active probes which come with a PSU and connect to any scope but they're a pain to use compared to manufacturer probes.

author: capt bullshot
author_rank: Super Contributor
timestamp: July 17, 2017, 10:02:28 am
content: Basically there are two reasons:1. Some probes must be compensated through software (DSP algorithm) on the scope side. So the scope needs to know how to compensate. Some probes offer various settings through the scopes operator panel, so the scope needs to know about the settings. Don't ever expect this to work across different brands.2. Marketing and market separation, active prohibition of use of third party devices (manufactureres want to sell more expensive probes to high end scope users instead of cheaper low end or third party)

author: peter-h
author_rank: Super Contributor
timestamp: July 17, 2017, 10:08:36 am
content: OK; many thanks.But what about single ended probes? I realise that the special connectors used will prevent compatibility e.g.but a basic one like thisshould be usable so long as you work out how to connect the external power to it (looks like a Lemo connector on that one).

author: capt bullshot
author_rank: Super Contributor
timestamp: July 17, 2017, 10:24:45 am
content: Yes, basic probes will work on any scope when supplied with the correct voltages and termination.

author: alm
author_rank: Super Contributor
timestamp: July 17, 2017, 10:30:26 am
content: Quote from: peter-h on July 17, 2017, 10:08:36 amSingle-ended active probes can have the same problem. Obviously passive probes should work apart from mechanical issues (I am not aware of any passive probes that use DSP for correction). As will older passive probes from before they started using DSP and identification EEPROMs. One thing that may still be controlled from the scope, even for older probes, is offset voltage.

author: peter-h
author_rank: Super Contributor
timestamp: July 17, 2017, 10:41:53 am
content: Can the Keysight MSOX3034 or LeCroy WS3034 work with simple passive probes like the one above?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 17, 2017, 10:48:05 am
content: Quote from: peter-h on July 17, 2017, 10:41:53 amAny of them can work with any passive probe as long as the probe's output fits the scope's voltage range and impedance. Passive probes in general aren't an issue as they don't require power or control.But the HP probe in your picture ..... is active, not passive.

author: peter-h
author_rank: Super Contributor
timestamp: July 17, 2017, 10:58:24 am
content: Whoops I meant ACTIVEI see the connectors on the more recent ones are not BNC... they can't be BNC because there is no way to access the bayonet on the "fat-box" probes whose body goes right up to the scope front panel. But if the scope is not BNC, that's a case of getting the right adaptors.What I am getting at is that the scope can't be insisting on EEPROM identification (like inkjet cartridges etc) IF it accepts PASSIVE probes with its 50 ohm input mode. An old style active probe will look just like a passive probe.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 17, 2017, 11:08:21 am
content: Quote from: peter-h on July 17, 2017, 10:58:24 amBoth KS and LeCroy probes on their low BW scopes (i.e. <8Ghz or so) use BNC. There's an extra connector for active probes but the signal is still transmitted via BNC.QuoteNo, there's nothing like ink DRM in a scope, and you can connect any probe as long as it's scope end looks and behaves like a normal passive probe (i.e. voltages and impedance matched to the scope).But the question is why would you want to? Especially LeCroy active probes are so cheap 2nd hand that there's no point to connect anything else unless you got it for free. System probes from the scope manufacturers just don't simply work, they are also generally well designed and nice to work with. Even for my Agilent Infiniium where the choice of system probes is a lot more limited I wouldn't go with anything else than a manufacturer active probe.If you spend so much money on a good scope don't skimp over the odds on probes.

author: capt bullshot
author_rank: Super Contributor
timestamp: July 17, 2017, 11:11:13 am
content: Yes, the scope will accept the signal from any active (single-ended or differential) or passive probe, as long as you are able to connect the signal and power the probe. Except for some scopes exceeding 1GHz bandwidth, all scopes accept standard BNC plugs and don't care if it's just a cable from a signal generator or an active probe thats needs to be terminated into 50Ohm (as long as the scope has a build in 50Ohm termination that you can turn on, and yes, you can always turn on the 50Ohm termination manually, except the scope doesn't have a 50Ohm termination built in).

author: peter-h
author_rank: Super Contributor
timestamp: July 17, 2017, 11:16:00 am
content: Thank you both.It thus looks like that the active probes which go right up to the scope panel have a connector which mates inside the BNC "panel socket" but doesn't engage the bayonet.Otherwise, how does this one work?

author: capt bullshot
author_rank: Super Contributor
timestamp: July 17, 2017, 11:20:12 am
content: This one locks the bayonet by turning that little lever you can see on top. It uses the bayonet, but isn't a real BNC, rather some kind of custom made locking mechanism that fits the BNC connector on the scope.

author: hs3
author_rank: Regular Contributor
timestamp: July 18, 2017, 09:28:49 am
content: Quote from: peter-h on July 17, 2017, 10:08:36 amThis probe has at least offset control interface in the Lemo connector in addition to the various supply voltages. But can be used with external supply.

author: nctnico
author_rank: Super Contributor
timestamp: July 18, 2017, 10:28:03 am
content: I think it is better to go for more universal probes so you are not getting into a vendor lock-in. OTOH the vendor specific probes allow things like offset to be controlled from the scope's user interface and so on.

author: alm
author_rank: Super Contributor
timestamp: July 18, 2017, 10:49:46 am
content: If you want high performance (e.g. bandwidth beyond a few GHz, high-sensitivity DC current probes, high-sensitivity differential probes), you are mostly limited to Tek/Keysight/Lecroy, which for the more recent probes means vendor-specific interfaces. Scope vendors know this, and treat probe technology as a unique selling point.

author: peter-h
author_rank: Super Contributor
timestamp: July 18, 2017, 03:45:10 pm
content: I have got a better price now for the WS3024 from Le Croy here in the UK, after I told him the USA is a lot cheaper. Still inflated though.I wonder if the function gen is truly worthless... you can get one of thesehttps://www.rigol-uk.co.uk/Rigol-DG1032Z-Waveform-Generator-p/dg1032z.htmfor less!

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 18, 2017, 04:59:10 pm
content: Quote from: peter-h on July 18, 2017, 03:45:10 pmOf course it's cheaper in the US, that has always been the case for pretty much anything.But now you also pay for the fact that the UK recently decided to commit economical suicide (Brexit), which is reflected in the large price increases of foreign-made goods. But hey, people voted for it, so it's OK.QuoteThe built-in AWG that can be found in many scopes isn't worthless, it's just not a very attractive offer if you actually have to pay full price for it because you can get an external AWG with better specs for the same or even less money. That might be different if the AWG option is thrown in as part of a deal, though.

author: JPortici
author_rank: Super Contributor
timestamp: July 18, 2017, 05:09:10 pm
content: in the end, we also received a perplexing quote from lecroynext week they're coming for a test drive, leave us a scope for some time.I hope to get the quote from keysight in time so we can compare notes and have a little chat..

author: peter-h
author_rank: Super Contributor
timestamp: July 18, 2017, 05:49:16 pm
content: "But now you also pay for the fact that the UK recently decided to commit economical suicide (Brexit), which is reflected in the large price increases of foreign-made goods. But hey, people voted for it, so it's OK."You might be surprised... after the fall in the value of GBP, my company's export sales went up 3x, which is worth way more than paying a bit more for the imported parts. I voted for Brexit, along with almost every other owner of a small business which actually makes something, and had to deal with the increasing EU regulation like the ROHS, ROHS2, REACH, etc nonsense. The national media in the rest of Europe of course likes to portray the vote as one solely by stupid bigoted xenophobic people, which is quite funny since several other countries would leave the EU tomorrow if they got a free vote2 sides to every coin... Electronics design engineers love the EU because it forces a lot of obsolescence and keeps them in jobsMany others love the EU too - basically the whole of the research community and especially academia - because they live off the grants.Only some things are cheaper in the USA. Normally the manufacturers align the pricing, to prevent people bypassing exclusivity agreements. In this case it is surprising how much difference there is. Not just in the published item prices (perhaps 20%) but in the much bigger value of the bundled discounts which in Europe are quoted under the table.

author: nctnico
author_rank: Super Contributor
timestamp: July 18, 2017, 06:20:07 pm
content: Quote from: peter-h on July 18, 2017, 05:49:16 pmSidenote: I don't see how preventing toxic materials from entering the food supply chain is a bad thing. There is more to doing business than making money. Unfortunately companies will only do the morally right thing when they really have to. Also if your business' profitability strongly depends on the value of the currency then there is something fundamentally wrong with it because it can go any direction.

author: peter-h
author_rank: Super Contributor
timestamp: July 18, 2017, 06:33:00 pm
content: AFAIK there was never any evidence that metals from scrapped electronic equipment enter the food chain. Most of the toxic stuff gets there from other sources.The gross profit margin in most manufacturing is about 75% of the selling price (e.g. if you sell a scope for 1k then the parts need to be 0.25k max) and this is not very vulnerable to currency moves. What is vulnerable (in both directions) to a small shift in price is the quantity sold.

author: nctnico
author_rank: Super Contributor
timestamp: July 18, 2017, 06:45:48 pm
content: Quote from: peter-h on July 18, 2017, 06:33:00 pmIt is not just about the electronics scrap but also about manufacturing of goods using toxic substances. Google 'China lead poisoning' for example and you'll see the problem. If there is no market for products with toxic materials then the toxic materials won't be used. But these things don't always happen far from your own front door. Over here in the NL we currently have a problem with a factory producing Teflon which has been dumping toxic waste in the surface water. This has lead to contamination of the drinking water.

author: Hydron
author_rank: Super Contributor
timestamp: July 18, 2017, 07:55:25 pm
content: I don't think we'll see a lot of the standards and regulations changing much. As an example when I designed and tested stuff in NZ (i.e. part of the former glorious empire) we followed a lot of EU standards (renamed as "AS/NZS" standards), despite the governments not being forced to use them. While we were not required to conform to ROHS etc for local sales we did anyway as the contract manufacturers were set up to do it, and it allowed us to CE certify our products for sale overseas.That said, I hate lead free for DIY and repairs, and I'm not convinced that there wasn't an element of European trade protection in implementing ROHS requirements.

author: Someone
author_rank: Super Contributor
timestamp: July 19, 2017, 02:36:05 am
content: Quote from: peter-h on July 17, 2017, 10:58:24 amNot entirely true, manufacturers can and do lock out probes they don't want used:https://www.eevblog.com/forum/testgear/1159a-differential-probe-modupdate/So you need to sever the identification link (eeprom and/or resistor strapping) before the probe is fully dumb and can be used.

author: peter-h
author_rank: Super Contributor
timestamp: July 19, 2017, 09:58:50 am
content: If I understand it correctly, that thread on the Agilent 1159A shows a probe which doesn't just have a simple BNC output, plus a separate power lead. I can't find good images on google but it seems to make a connection to the BNC plus some other connections next to it.I can completely see such a probe is not going to be back-supported.But any probe which has a simple BNC output plus a separate power cable should work with any scope.The offset adjustment can't be a big issue. One has to move traces up and down when using a scope anyway...Hydron- I agree with you; not much will change for big companies, or companies which export to customers who are picky (basically large companies who demand the declarations signed in blood and with a DNA specimen attached). But there is a more subtle and beneficial effect: IF you can sell non EU-compliant products in the home market, that undermines the automatic "everything has to be compliant" presumption, which undermines surveillance and enforcement and allows small companies to start up and grow. Just like Ebay and Amazon facilitate currently (you can sell anything there, with no questions asked) except they are not really suitable for B2B stuff. I started in electronic mfg in 1978 and back then you could have a small business selling B2B. Today, the entire consumer market is off limits to small players and there are just small niches left in B2B, which makes it really hard to start a business in electronics (and much else).

author: David Hess
author_rank: Super Contributor
timestamp: July 19, 2017, 12:10:25 pm
content: Quote from: peter-h on July 19, 2017, 09:58:50 amThat is not what offset adjustment is for.Passive low impedance probes may implement offset so the input current can be adjusted to zero at input voltages other than ground. This prevents the low impedance of the passive probe from upsetting the operating point of the circuit and allows more accurate voltage measurements.Active probes use offset to shift their limited input voltage range to bracket the signal which is important for them because they have horrible overload recovery. Sampling inputs also support this but since they are immune to overload, they use it to allow higher sensitivity measurements of large signals like the 7A13. See below.Oscilloscope inputs use offset so that their high sensitivity ranges can be used to make measurements at large DC offsets. In the case of the Tektronix 7A13, this is like having a position control which operates over 20,000 divisions; at 1mV/div, it can make measurements over a +/- 10 volt range. Many DSOs support separate position and offset controls although usually not such an extreme offset range.

author: peter-h
author_rank: Super Contributor
timestamp: July 21, 2017, 02:34:26 pm
content: That sounds like there must be a D-A converter inside the probe, whose output drives the ground of the input amp, and a level shifter circuit to bring it back down to the output to the scope which obviously has to be power ground referenced. And some user interface in the scope for setting the D-A output.

author: alm
author_rank: Super Contributor
timestamp: July 21, 2017, 02:52:40 pm
content: Or just an analog voltage generated by the scope (DAC or even a potentiometer). This is how it worked in older probes. Some probe power supplies have pots for offset adjustment.

author: peter-h
author_rank: Super Contributor
timestamp: July 26, 2017, 10:25:13 am
content: Is the LeCroy WS3024 (200MHz) with the 350MHz software key applied *exactly* the same as the 3034, including all accessories?I know this is a bit silly but presumably the front label says "200MHz", or does the upgrade come with a sticker?Also, since this seems to be the 500MHz model anyway, how are the bandwidth degradations implemented? I might go for the 200MHz model because it is so much cheaper...Also this scope supports ETS and does that work with a 200MHz or 500MHz analog input amp? I would be amazed if they have analog switches which switch in some capacitors to slow down the front end amp!

author: JPortici
author_rank: Super Contributor
timestamp: July 26, 2017, 10:33:53 am
content: I Have the lecroy rep coming in a few hours with a 3024I may ask some questions

author: peter-h
author_rank: Super Contributor
timestamp: July 26, 2017, 10:43:20 am
content: You could ask him what is the best he can do with the MSO (16 logic inputs) and EMB (SPI etc) options

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 26, 2017, 10:46:15 am
content: Quote from: peter-h on July 26, 2017, 10:25:13 amYes. The hardware is identical for I believe up to 500MHz.QuoteNot silly at all, and yes, BW upgrades should come with a new set of stickers.QuoteThe steps are 200MHz - 350MHz - 500MHz - 750MHz (and 1Ghz for the Siglent variant but not for the LeCroy), as I said as far as I remember the hardware up to 500Mhz is all the same, the 750Mhz variant has a different front-end (so needs to go back to LeCroy for upgrade).QuoteNot sure what you're saying. ETS works with any signal that lies within the voltage levels and BW limits of the scope (although if its useful is a different question).

author: peter-h
author_rank: Super Contributor
timestamp: July 26, 2017, 10:54:49 am
content: The exact way that ETS works (or doesn't) will be dependent on the front end, before the ADC.Let's say for example that the bandwidth crippling is implemented with a lowpass filter on the waveform displayed on the LCD i.e. wholly in software. That would be the easiest (and the most cynical) way to do it. It would be very easy to do because it doesn't matter whether it takes 10ms or 50ms to draw the picture on the LCD.But if they actually modify the BW of the input amp that will affect ETS too because the waveform is already BW-crippled.What I am getting at is that a 70MHz scope which is actually 500MHz might be giving you 500MHz with ETS i.e. when looking at any repetitive waveform. Only with single shot signals it will be BW limited to 70MHz.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 26, 2017, 11:33:53 am
content: Quote from: peter-h on July 26, 2017, 10:54:49 amErr, no. ETS is a sampling mode, and if it works depends on the characteristics of the input signal.QuoteIt wouldn't be very easy, it would require a real-time fourier transformation, stepped removal of the excess frequency components, and then a real-time inverse FT to get the waveform back. Even on a high end scope with powerful processing this won't result in very good update rates. And it would be a silly way to do this as limiting BW in hardware is much easier, especially when considering that better DSOs already use DSPs to get the required linearity from their front ends.QuoteNot sure what you're getting at. The analog BW is what it is, independent of the sampling mode (of which ETS is only one).If you buy a 200Mhz scope then changing the sampling mode will not get you more BW1.QuoteSuch a scope doesn't exist. As stated before, ETS is a sampling mode and doesn't affect the analog BW which is determined by the scope's front-end and which is generally static.Also, I get the impression you underestimate the requirements for ETS to be actually useful. Most waveforms people consider as "repetitive" actually aren't truly repetitive.1It appears that some of HP's old Infiniium 54800 Series scopes show a slightly increased BW in ETS mode than in normal sampling mode, probably caused through different parameters feed into the scope's DSPs. But these are exceptions.

author: David Hess
author_rank: Super Contributor
timestamp: July 26, 2017, 11:57:09 am
content: Quote from: peter-h on July 26, 2017, 10:54:49 amI know of old examples where this was done and the only difference it makes is that the trigger point shifts because of delay through the low pass filter.QuoteI know of no examples where this is the case. Like Wuerstchenhund says, equivalent time sampling does not care about hardware bandwidth limitations. ETS combines multiple single shot acquisitions by aligning them in time by measuring the delay between the trigger and sampling clock.Quote from: Wuerstchenhund on July 26, 2017, 11:33:53 amIt just requires a FIR filter so a bunch of multiply-accumulate operations. Many DSOs implement this in real time and any digital equalization is done the same way.QuoteI have seen this on high bandwidth DSOs. I think it comes about because the processing used to minimize aliasing is not required or even desired in ETS mode where the sample rate is much higher. Switching to ETS mode removes the Gibb's phenomena for the same reason.

author: peter-h
author_rank: Super Contributor
timestamp: July 26, 2017, 01:00:47 pm
content: Thank you all...So is the 3024 + 350MHz exactly identical to the 3034, and does anyone know how the BW limit is implemented?Indeed, bandwidth-limiting a displayed waveform would be trivial; just a low pass filter. You could do it with a 4MHz Z80

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 26, 2017, 02:12:47 pm
content: Quote from: David Hess on July 26, 2017, 11:57:09 amTrueQuoteI've never seen this on any scope I had an opportunity to test its BW limit in real-time and ETS/RIS mode, which were quite a few including my own 3Ghz LeCroy WavePro 7300A, my trusty old 13Ghz DSO90k at work, a few models of the Keysight DSO9k, LeCroy HDO4k/6k, WP7zi-A, WM 8zi-A and a few other scopes including a 65Ghz LabMaster 9zi-A (where RIS works only for signals <25GHz).It also wouldn't make a lot of sense to change the front end's BW envelope because while, as you said, aliasing might not be an issue in ETS mode because of the high sample rate, increasing the BW also means increasing the noise floor, i.e. potentially introducing non-repetitive artefacts which wwould degrade the waveform integrity.But then, ETS is pretty pointless these days because as long as all frequency components of a signal to measure are within Nyquist-Shannon (fsignal< 2 * fsampling) then using sin(x)/x interpolation will always present a true waveform.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 26, 2017, 02:20:43 pm
content: Quote from: peter-h on July 26, 2017, 01:00:47 pmConsidering that this is just a SW code it's very likely done via a DSP in the front end.

author: nctnico
author_rank: Super Contributor
timestamp: July 26, 2017, 02:44:41 pm
content: Quote from: Wuerstchenhund on July 26, 2017, 02:20:43 pmPre-amplifiers with adjustable bandwidth have been available for decades (for example: the Tektronix TDS500/700 series used this). Often the bandwidth limits (like 20MHz) are implemented the same way.

author: David Hess
author_rank: Super Contributor
timestamp: July 26, 2017, 04:01:39 pm
content: Quote from: Wuerstchenhund on July 26, 2017, 02:12:47 pmI am referring to the sin(x)/x interpolation filter and the bandwidth enhancement filter. I saw it on an Agilent multi-GHz DSO which supported selectable RTS and ETS but it actually applies to any DSO where you can manually select modes. (1) In RTS mode using a fast impulse from a reference level pulse generator, the distortion caused by filtering was pronounced with preshoot and overshoot. Switching to ETS completely removed it. Agilent and Tektronix application notes on bandwidth enhancement show lots of examples of the RTS case but not of the ETS case.QuoteIf ETS is acceptable, then either averaging or an FIR filter based on the the ETS sample rate and not the real time sample rate can be used to reduce noise without distorting the waveform. This however can be misleading as with the Tektronix MSO5000 series DSOs and I assume others. For them, the hardware and DSP bandwidth limiting produce different results. Unfortunately when I ran across this, the Tektronix application engineers were as baffled as I was.QuoteIf you measure a fast edge, then sin(x)/x interpolation will cause distortion do to signal components close to the Nyquist frequency. A good example of this occurs when you view a fast edge on a 100 MHz Rigol DS1074Z is while it is in 4 channel mode limiting it to 250 MS/s. Any RTS DSO under these conditions will produce the same result which are *not* as accurate as the result produced by ETS.The more annoying thing about this example is that the display of the interpolated waveform *changes* depending on the number of channels being used as if the number of channels is altering the signal which of course it is not. And you cannot resolve this by disabling sin(x)/x interpolation even if the DSO lets you because sin(x)/x is still used for determining the trigger point.(1) Beyond economics, this is a good reason to drop ETS support or at least drop being able to manually select between ETS and RTS. Users are more likely to question the performance of the DSO when these different sampling modes produce different results and the legacy ETS mode produces results which more closely match an analog or sampling oscilloscope.

author: alm
author_rank: Super Contributor
timestamp: July 26, 2017, 04:10:40 pm
content: Quote from: David Hess on July 26, 2017, 04:01:39 pmSignal components close to the Nyquist frequency, or beyond the Nyquist frequency? It is not hard to imagine a 100 MHz scope's input filter (which is most likely Gaussian) letting through frequencies beyond 125 MHz. You would need a bandwidth-limited edge to be sure. An input filter of fsample/2.5 is very aggressive for a Gaussian filter.

author: nctnico
author_rank: Super Contributor
timestamp: July 26, 2017, 04:55:50 pm
content: The limit of sin x/x reconstruction is around 0.4fs and beyond that you'll get odd behaviour. ETS doesn't have this issue so it could be usefull in some cases at the expense of being slower and needing a repetitive signal. Either way it is not a good idea to blindly trust what is on the screen of an oscilloscope. You always have to take it's limits into account.

author: David Hess
author_rank: Super Contributor
timestamp: July 26, 2017, 05:16:01 pm
content: Quote from: alm on July 26, 2017, 04:10:40 pmBoth but the ones beyond the Nyquist frequency are the primary problem. The 100 MHz bandwidth in my example yields a 3.5 nanosecond transition time for a single pole rolloff and *that* is the filtering. DSOs typically do not include anti-aliasing filters as such because the tradeoff is not worth it and they cause more problems than they solve. 250 MS/s sampling of a 3.5 nanosecond edge from a 100 MHz oscilloscope input bandwidth produces significant artifacts if sin(x)/x interpolation is used.On a real digitizer with non-linearity, the signal components just below Nyquist mix with the sampling frequency to produce signals above Nyquist which further distort the result. If it were not for this, the sin(x)/x reconstructed waveform would at least be stable. They are always making better digitizers so this has become less of a problem as time goes on. Some older DSOs were particularly bad in this regard, mostly do to interleaving, and Agilent teased Tektronix about it in their application notes.Quote from: nctnico on July 26, 2017, 04:55:50 pmI trust my sampling and ETS oscilloscopes. But maybe the lesson to be learned here is not to accept the accuracy of bandwidth limited edges on an oscilloscope. Personally I think this problem is worse with DSOs because reconstruction adds more distortion. If you are dealing with 3.5 nanosecond edges on your 100 MHz DSO, then you need a higher bandwidth DSO to get accurate results which should not be surprising.

author: tautech
author_rank: Super Contributor
timestamp: July 26, 2017, 06:36:23 pm
content: Quote from: peter-h on July 26, 2017, 10:25:13 amI wouldn't be sure that the probe BW was the same.

author: JPortici
author_rank: Super Contributor
timestamp: July 26, 2017, 07:16:35 pm
content: the datasheets mentions 250 and 500 MHz passive probes but doesn't tell which gets what...i would think 250 MHz for the 200 MHz version, 500 MHz for 350,500,750 MHz versions?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 27, 2017, 02:09:47 pm
content: Quote from: David Hess on July 26, 2017, 04:01:39 pmWhich model?QuoteAs stated before not in my experience, and I tested the real BWs of quite a few high BW scopes with our Keysight E8267D 31GHz/44GHz sythesizers connected to the scope with proper RF cabling suitable for the used frequency range. There's been zero difference in the location of the -3dB point or the brickwall filter between real-time and ETS on any of the tested scopes (aside from the LabMaster, where RIS actually limited the scope BW but then this scope uses DBS).QuoteThis is wrong. Sin(X)/x remains valid right up to the Nyquist-Shannon frequency, aliasing will only cause distortions beyond Nyquist-Shannon.QuoteNo, that's not agoodexample. The DS1074Z, while being cheap, isn't really a good representation of a modern decent DSO, not just because Rigol's demonstrated inability to design a proper oscillator. From what I remember from various threads, a hacked DS1074Z has an analog BW exceeding 150MHz, and the upper end is not really well defined (it's not Gaussian, it's not brickwalled, it just is something). Being a bottom-of-the-barrel scope, it's no surprise that the sample rate in 4ch mode drops to a point where the Nyquist-Shannon frequency is much lower than the analog BW. It should be pretty obvious why watching signals with frequency contents above the scope's Nyquist-Shannon frequency results in crap.But that is hardly relevant for any of the scopes discussed here, which all not only have properly defined behavior at their BW limits but also max sample rates that vastly exceed the sample rate required to maintain the Nyquist-Shannon frequency above their real-life BW limit.Quote from: nctnico on July 26, 2017, 04:55:50 pmNo, it's not. Sin(x)/x is only limited by the resolution and accuracy of your scope's timebase (x). There's no inherent limit in the function itself.QuoteETS has pretty much the same issue as it also relies on the resolution and accuracy of the scope's timebase, although because ETS builds up the waveform over a series of subsequent acquisitions it can potentially achieve a somewhat higher accuracy, however how much of that you really get still depends on the analog BW of the scope.Besides, you wouldn't believe how much people generally underestimate the importance of true repetitiveness when using ETS. Not everything many consider repetitive is truly repetitive. ETS lives and dies with true repetitiveness.QuoteTrue, but that has been the same for pretty much every test instrument.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 27, 2017, 02:11:07 pm
content: Quote from: JPortici on July 26, 2017, 07:16:35 pmAll WS3k we got came with 500MHz probes, even the few 200Mhz variants we have.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: July 27, 2017, 02:28:14 pm
content: Quote from: Wuerstchenhund on July 27, 2017, 02:09:47 pm+1 Have suspicion that Rigol does (similar to) this, only other way around:https://www.maximintegrated.com/en/app-notes/index.mvp/id/3853Possibly trickery is (mostly) in software, this why Sinc cannot be turned off in normal manner."Decent DSO" will not demonstrate this and will match RTS-Linear/RTS-Sinc/ETS quite reasonably.

author: David Hess
author_rank: Super Contributor
timestamp: July 27, 2017, 04:16:27 pm
content: I had a long post about ETS and sin(x)/x but the Gateway 502 error with something about maintenance in March ate it.

author: peter-h
author_rank: Super Contributor
timestamp: July 27, 2017, 04:19:32 pm
content: I am now looking at the 200MHz version as it is much cheaper and with the MSO and EMB options it should be within the budget.And maybe one day there will be a special offer going on the 350MHz or even 500MHz software key (or I might be able to pick it up somewhere...). This scope is bound to get hacked one day, because this pricing policy is really cynical.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 27, 2017, 05:15:04 pm
content: Quote from: David Hess on July 27, 2017, 04:16:27 pmWhen that happens you should be able to get your text back by clicking on your browser's back button.The unpredictability of this forum software is one reason why I type my text in a text editor and then copy it in the browser window.Quote from: peter-h on July 27, 2017, 04:19:32 pmUnlikely, considering how aggressive LeCroy is when it comes engaging all attempts of hacking their key system. Which is somewhat understandable, as they use the same key system for all of their non-entry-level scopes since the old WaveRunner LT from 1998 right up to the >$1M 100GHz LabMaster 10zi. Unlike other vendors, LeCroy also still sells keys for all these scopes going back to that 1998 WaveRunner LT, so they are very motivated to fight against any hacking attempts.QuoteNo, it isn't. It's exactly the same for all big test & measurement manufacturers. Just for fun, go and ask how much Keysight charges for the serial decode options, mask testing or the N8900A InfiniiView PC software. And then, if you think these are expensive, go and check the list price for similar option for Rohde & Schwarz RTM, RTE and RTO scopes.That's why negotiating is so important.

author: peter-h
author_rank: Super Contributor
timestamp: July 27, 2017, 05:38:36 pm
content: My point is that you can get an awful lot of extra functionality enabled, for the 200-350 price delta, i.e. the WS3024+MSO+EMB.Currently I am looking at a US supplier, who I obviously won't nameIf anyone can do a great deal on WS3034+MSO+EMB, I am "all ears".

author: nctnico
author_rank: Super Contributor
timestamp: July 27, 2017, 06:07:34 pm
content: Quote from: Wuerstchenhund on July 27, 2017, 05:15:04 pmEven if it means losing sales... nowadays hackability means sales because nobody is going to pay for common options like decoding.

author: blacksheeplogic
author_rank: Frequent Contributor
timestamp: July 27, 2017, 08:01:10 pm
content: Quote from: nctnico on July 27, 2017, 06:07:34 pmDepends on who your target market is.

author: nctnico
author_rank: Super Contributor
timestamp: July 27, 2017, 08:13:57 pm
content: Quote from: blacksheeplogic on July 27, 2017, 08:01:10 pmThe cheaper brands are getting much better so they must be eating into the A-brand's market share pretty bad.

author: peter-h
author_rank: Super Contributor
timestamp: July 27, 2017, 08:49:37 pm
content: Currently Le Croy are sticking to the $500 FG being bundled and won't let you drop that one out to save the $500.They also always want $1500 for the logic input option. Don't they populate the PCB anyway, like Keysight do, so the only extra cost to them is just the logic probe?Which scope was it that required the logic option in order to do serial decoding? I think it was the Instek one... but Instek make the Le Croy scopes.

author: tautech
author_rank: Super Contributor
timestamp: July 27, 2017, 09:11:37 pm
content: Quote from: peter-h on July 27, 2017, 08:49:37 pmThere's all sorts of politics come into play with rebrands and maybe it's a good time to take a step back and have a rethink about what youmusthave in a scope and better value for money options.

author: peter-h
author_rank: Super Contributor
timestamp: July 27, 2017, 09:38:45 pm
content: What I want are the logic input and SPI etc decoding.It clearly looks like LC are working hard to prevent the box going for too little, by always bundling the FG option at $500.It would be pretty weird if the EMB option (frequently bundled in the USA right now) required the MSO option ($1500 always)

author: nctnico
author_rank: Super Contributor
timestamp: July 27, 2017, 10:01:01 pm
content: Quote from: peter-h on July 27, 2017, 09:38:45 pmBuy the GW Instek MSO2000 and be done with it.

author: tautech
author_rank: Super Contributor
timestamp: July 27, 2017, 10:01:42 pm
content: Quote from: peter-h on July 27, 2017, 09:38:45 pmYeah but you want the large display too so that cuts down choice some.In the 200-300 MHz range there are other options, moreso if you consider smaller displays.

author: JPortici
author_rank: Super Contributor
timestamp: July 27, 2017, 10:47:45 pm
content: Quote from: peter-h on July 27, 2017, 04:19:32 pmhave you had the chance to actually try the lecroy?our loaner should arrive tomorrow or at worst monday (rep couldn't lend us his)but for the little i tried both the lecroy and the keysight... i suggest you do try both of them and then decide what you need most between probing around and not so common options, or waveform analysisi'll post my thoughts in a couple of days...

author: JPortici
author_rank: Super Contributor
timestamp: July 27, 2017, 10:55:13 pm
content: Quote from: Wuerstchenhund on July 27, 2017, 05:15:04 pmwell, keysight has shown to be very eager to give us a good deal for the scope (plus the additional free 1000x we don't really need, maybe that can be traded for a decode or two from what i heard)otherwise the price of options is just insane, which is why they promptly suggest for you to buy the bundle insteadI tried the infiinium software, that's sick! also because i can import data from other scopes on it

author: peter-h
author_rank: Super Contributor
timestamp: July 28, 2017, 05:52:14 am
content: Spec for spec I have been unable to get any Keysight offer, even ex leasing used scope, which is within 1.5x of the Le Croy WS3034. I spent a lot of time on this.The one thing KS have is ARINC429 decoding but you can buy an ARINC429 to RS232 converter for the official cost of a Keysight 100MHz passive probe

author: JPortici
author_rank: Super Contributor
timestamp: July 28, 2017, 06:04:18 am
content: don't know what to say, i called both offices to ask for a quote and test for the business i work at, i got called back the following day to chat a bit with the local reps and set up a meeting with them in our test/prototype lab a couple of days after.both meetings very pleasant and of help.2 days after meeting 1 loaner 1 arrived, today is 2 days after meeting 2 loaner 2 arrivedIt would suprise me if none of them would do that in UK... Their job description is to literally go to potential clients and showcase the instruments and sell, sell, sell.in both cases we were presented with solutionsdon't underestimate the possibility to trigger on decodes you actually use.Thought it was a nuisance, weren't prepared to pay for it, but the first test i did with the KS loaner was to trigger on errors on SENT enhanced channels... SENT is a slow protocol already... and enhanced channels transmit a full message divided in packets over 8 standard messages.. other hardware i had that decoded this protocol either failed due to low samplerate at timebase / low memory combo and/or couldn't trigger on it so it failed to show me this particular CRC error i didn't expect to have (code apparently tested and true)now it's up to me to find out if it's a bug in the software, or a problem in hardware because other boards never showed this problemand you can't really do that with a logic analizer / protocol datalogger. you have to look at both the actual waveform and the code

author: peter-h
author_rank: Super Contributor
timestamp: July 28, 2017, 07:02:18 am
content: The way I have seen this sort of thing work here in the UK is that big firms allocate a lot of resources to "getting into" a sizeable company, i.e. banking on future business. Small people like me get nothing.It is curious that there were nousedDSOX scopes of that spec; it was my #1 choice. They do come up but at nearly-new prices. Perhaps if one waited a year... but clearly people keep this stuff because it is good. You don't get used ones coming up except at bankrupcy auctions etc.

author: nctnico
author_rank: Super Contributor
timestamp: July 28, 2017, 08:08:44 am
content: Quote from: peter-h on July 28, 2017, 07:02:18 amThere are always several on Ebay including from Keysight's own Ebay store. The latter would be a wise choice if you care about warranty.

author: nfmax
author_rank: Super Contributor
timestamp: July 28, 2017, 08:19:09 am
content: There are still a couple of ex demo offers fromhttps://www.keysight.aspen-electronics.com/ex-demo-equipment. They are an authorised distributor: I've bought a couple of second user scopes from them in the past.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 28, 2017, 09:14:38 am
content: Quote from: nctnico on July 27, 2017, 06:07:34 pmLet's be honest, the only people hacking are hobbyists, and for this group even the WaveSurfer 3000, which is the by far cheapest X-Stream scope, is usually pretty much at the upper end of what this group can afford.Most scopes however don't go to individuals, they go to businesses which in general want to have legitimate options.However, you're right however that pretty much no-one pays for options when buying a scope, as they are usually always part of the deal that is agreed. However, businesses occasionally do buy options after the scope purchase.I guess the issue for LeCroy isn't really that a broken hobbyist wants to enable some options in his old scope (which is why they often give options away for free to hobbyists in the Yahoo group), it's the risk that the hack spreads that they want to avoid.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 28, 2017, 09:24:00 am
content: Quote from: nctnico on July 28, 2017, 08:08:44 amThe only instruments that have full warranty are Keysight's CertiPrime instruments, used gear usually only comes with 60 days or so of warranty.Also, warranty isn't much of a problem with Keysight as long as the instrument is still under mainstream support. Keysight offers so-called Repair Agreements which essentially are just warranty packs. They are usually surprisingly reasonable (especially considering that Keysight's prices are usually at the upper end of the market), and to buy it the only condition is that the instrument is fully working. It doesn't matter how old it is, or where it has been bought from.Pretty much all my Agilent/Keysight gear aside from my HP GPSDO and my DSO8064A (both too old) has got Repair Agreements on it.

author: nctnico
author_rank: Super Contributor
timestamp: July 28, 2017, 09:58:16 am
content: Quote from: Wuerstchenhund on July 28, 2017, 09:24:00 amAFAIK you can always get repair agreements on Keysight equipment as long as it is supported.

author: peter-h
author_rank: Super Contributor
timestamp: July 28, 2017, 11:57:43 am
content: Aspen are very expensive. Or, putting it another way, here in the UK the prices are high and used kit sells for only slightly below brand new.I often check Ebay for "DSOX" and just see lots of thiswhich is IMHO overpriced.As I said, there is very little used equipment for sale, in this category.EDIT: I am getting a WS3034+FG+MSO+EMB, from the USA.

author: nctnico
author_rank: Super Contributor
timestamp: July 28, 2017, 05:08:24 pm
content: When it says 'make offer' make an offer! There is a 50-50 chance you can make a good deal after some negotiation.

author: peter-h
author_rank: Super Contributor
timestamp: July 28, 2017, 06:04:07 pm
content: I went around that one a few times. They won't budge. Anyway I have the WS3034 on order now. Probably 30-40% off the UK price.

author: peter-h
author_rank: Super Contributor
timestamp: July 29, 2017, 06:17:16 am
content: Is there a list of active probes which will work with the WS3034?LeCroy list only the ZS1000 which sure enough is on Ebay too, at about $1000 for a new one. One can buy them from distis for less...There are several others with the same "box" style which look like they have the same connector. Ebay # 272663607402 is an HPF-1000 which again looks similar style. There is an AP-020, likewise.Ebay item 172796394593 lists as "Agilent/Lecroy AP020 Active FET Probe, 1GHz". Did these two really share the same probe interface?There is also a ZS1500, going for a lot less than the ZS1000.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: July 29, 2017, 04:55:47 pm
content: Quote from: peter-h on July 29, 2017, 06:17:16 am"Work" as in "work" or as in "officially supported"?Pretty much all LeCroy active probes with LeCroy ProBus interface will work on the WS3k.Officially supported however are only newer probes like the ZS Series, and there only the 1Ghz variant as a higher probe BW doesn't make much sense when the scope BW is 750Mhz or less.QuoteWith some patience you can find them cheaper on ebay, too.QuoteThis is the LeCroy-specific ProBus interface. But be careful, there's also ProLink, which is for high BW scopes and which looks similar but use a different connector. ProLink probes don't fit on ProBus scopes like the WS3k.QuoteBoth work fine with the WS3k.QuoteNo, that's just seller error. HPAK (HP/Agilent/Keysight) uses a different probe interface than LeCroy. However, these active probes were made by Preamble for LeCroy, and they also made a version for HPAK which uses the same electronics but instead of the ProBus connector at the probe body's rear end they had a cable which ended in a connector which fits HPAK's interface. Also, the probe color was grey/beige instead of charcoal/dark grey for the LeCroy variant.QuoteThis one also works on the WS3k.Personally I'd recommend the HFP Series and the AP033/AP034 500Mhz/1GHz differential probes, which can often be found pretty cheap.

author: peter-h
author_rank: Super Contributor
timestamp: July 29, 2017, 08:14:09 pm
content: Many thanksAre the differential probes usable as a normal probe? There doesn't seem to be much difference in the way they look. Both types of "1GHz" active probes need the ground pin really close to the signal pin (usually to touch a ground plane).Obviously the answer should be "yes" but I wonder if there is some gotcha...

author: David Hess
author_rank: Super Contributor
timestamp: July 29, 2017, 10:04:03 pm
content: Quote from: peter-h on July 29, 2017, 08:14:09 pmLow voltage differential probes may be used in place of low voltage single ended active probes by shorting one of the inputs to ground. The Tektronix P6046 even came with an adapter to do this. Differential probes used this way have twice the noise of an equivalent single ended probe but that is seldom a limitation.More common is to connect the other input to the local ground where the signal is being measured. So the differential probe is not being used to sample a differential signal but instead is removing noise from the ground loop that a single ended active probe would create and see. For example, a differential probe can subtract ground bounce.

author: Someone
author_rank: Super Contributor
timestamp: July 30, 2017, 12:10:49 am
content: Quote from: peter-h on July 29, 2017, 08:14:09 pmUsually there is a restrictive voltage range compared to passive probes, so active probes can't be used for everything. But even comparing active probes to each other the differential probes tend to have more noise when used single ended. Once you have a few probes you realise you could do with many many more.

author: Electro Fan
author_rank: Super Contributor
timestamp: July 30, 2017, 01:06:13 am
content: Quote from: tggzzz on July 06, 2017, 11:45:30 amSorry for being late to this thread. What Tek model is this? Thx

author: tggzzz
author_rank: Super Contributor
timestamp: July 30, 2017, 07:36:15 am
content: Quote from: Electro Fan on July 30, 2017, 01:06:13 amIt is a special purpose sweet portable "scope" that, when properly maintained, can be used in water and submerged to 1 ft. I don't want to think that the voltage from the focus pot is directly on a front panel potIt is a Tek 1502 TDR. I'm just about to take mine out into a wet (probably, looking at the rain radar) field (literally) to show the quality of a 50ohm load - the reflection from theconnectorcan be measured to be a VSWR of 1.1.Since mine isn't properly maintained, I think I'll keep itinthe car

author: peter-h
author_rank: Super Contributor
timestamp: July 30, 2017, 10:14:39 am
content: The AP-034 seems to have a max diff voltage range of 0.4V which makes is unsuitable for logic probing

author: Someone
author_rank: Super Contributor
timestamp: July 30, 2017, 11:06:11 am
content: Quote from: peter-h on July 30, 2017, 10:14:39 amIts the same Preamble probe as branded the Agilent 1159A, they're designed to be used with matched attenuators:http://cdn.teledynelecroy.com/files/manuals/ap034_inst_manual.pdfhttp://literature.cdn.keysight.com/litweb/pdf/01159-92001.pdf

author: peter-h
author_rank: Super Contributor
timestamp: July 30, 2017, 01:07:23 pm
content: Great; thanks. I better make sure that these attenuators come with any probe found on Ebay...

author: peter-h
author_rank: Super Contributor
timestamp: October 02, 2017, 07:29:10 pm
content: Well, after all that, I bought the Le Croy WS3034. And a 1GHz active probe, $500, refurbished from the LeCroy shop on US Ebay.It is really excellent.One thing we could not find today was decoding data on RS422/485 i.e. the difference between two signals. There is one option called RS232, and one called UART which I assume is the TTL level at a microcontroller i.e. inverted version of RS232.

author: nctnico
author_rank: Super Contributor
timestamp: October 02, 2017, 08:06:01 pm
content: Technically: RS485 is (like RS232, RS422, etc, etc) only an electrical interface specification so you can run any kind of bit pattern over it which forms a communication layer.However, if there is a UART signal over any of these kind of links you should be able to decode it using the UART decoder. It is a matter of setting the right threshold and polarity (and the regular UART parameters ofcourse).

author: peter-h
author_rank: Super Contributor
timestamp: October 02, 2017, 09:16:36 pm
content: What is the difference between UART and RS232? You can set a threshold for either mode.I know what you mean about interface versus protocol etc and I have run e.g. Manchester using RS485 chips, but normally RS422/485 is just a differential version of RS232. The data encoding is the same i.e. NRZ, with a start bit, x data bits, 1 stop bit... To decode this in the correct differential way the scope would need a facility for subtracting two channels, otherwise the decoding is just like RS232.

author: rsjsouza
author_rank: Super Contributor
timestamp: October 03, 2017, 06:49:19 pm
content: Quote from: peter-h on October 02, 2017, 07:29:10 pmAccording tothis datasheet, the UART is a bit more configurable.

author: tggzzz
author_rank: Super Contributor
timestamp: October 03, 2017, 07:49:38 pm
content: Quote from: rsjsouza on October 03, 2017, 06:49:19 pm... and to grok whatisn'tbeing said and whatisn'tbeing specified.

author: rsjsouza
author_rank: Super Contributor
timestamp: October 03, 2017, 09:35:11 pm
content: Quote from: tggzzz on October 03, 2017, 07:49:38 pmGood one!

author: peter-h
author_rank: Super Contributor
timestamp: October 11, 2017, 06:20:25 pm
content: Many thanks, rsjsouza. There is way more functionality in this than I had realised, or saw in the config pages.

author: peter-h
author_rank: Super Contributor
timestamp: October 24, 2017, 07:20:12 am
content: Does the WS3034 have the capability to look at e.g. RS422 the correct way i.e. decode the two signals differentially?

author: Hydron
author_rank: Super Contributor
timestamp: October 24, 2017, 07:38:08 am
content: Can you use a maths function to find the difference between the two signals, then run the decode on that result?

author: borjam
author_rank: Unknown
timestamp: October 24, 2017, 07:51:27 am
content: Quote from: Hydron on October 24, 2017, 07:38:08 amI would guess it's possible to use "MATH" as a source on a LeCroy. I was surprised by the ancient 9400 and how it allows you to stack operations using "MATH" as a source.That said, in order to debug RS422/RS485 I think that a differential probe is almost mandatory. Especially with long cable runs. Common mode voltages can be a problem otherwise.I use a Hameg HZ109 myself. You don't need a lot of bandwitdh.