Tektronix 1-3 GHz touch screen color DSO back in 1989 ! - Page 1
Forum section: electronics / testgear

author: snoopy
author_rank: Frequent Contributor
timestamp: August 20, 2017, 01:15:03 am
content: Do people know that Tek had a touch screen, full color DSO with 10 bit ADC back in 1989 ? The 11403 had 1GHz bandwidth and the later 11403A had 3GHz bandwidth with 2GHz trigger bandwidth !! Anyone still using one of these old war horses ?Check out this crusty old VHS video !!Official datasheethttps://accusrc.com/uploads/datasheets/4351_11403A.pdfhttp://w140.com/tekwiki/wiki/11403

author: David Hess
author_rank: Super Contributor
timestamp: August 20, 2017, 03:19:14 am
content: The real time sample rate was pretty low on these so they relied on equivalent time sampling and were not suitable for general purpose use. There were other mainframes in this series which supported real time sampling at rates to support their 1 GHz bandwidth.They are certainly impressive but this was the start of test instruments from Tektronix which lacked service documentation so relatively minor problems are major problems.

author: bjcuizon
author_rank: Frequent Contributor
timestamp: August 20, 2017, 04:00:27 am
content: The touchscreen is just a crt but with Multiplexed IR Leds and receivers on the sides of the crt. Basically, as you touch a certain point of the screen, you interrupt the IR light that is pointed at an IR receiver. Check this out:Mr Carlson's Tek Scope

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 20, 2017, 04:29:50 am
content: Quote from: snoopy on August 20, 2017, 01:15:03 amYes, but these were sampling scopes, i.e. the real-time sample rate was abysmally low, so it was only really useful for truly repetitive signals.Also, touch screens weren't really new back then, computers with similar touch technology (IR LED scanners) have been available earlier than that.QuoteYes, but so what? Back in 1989 HP had the 54120B which could go up to 50Ghz with the 54124A 4ch test set:And Philips had the PM3340 2GHz 10bit 50kSa/s sampling scope back in 1988:QuoteI doubt it. Sampling scopes are useful only in very few situations.

author: David Hess
author_rank: Super Contributor
timestamp: August 20, 2017, 07:04:12 am
content: Quote from: Wuerstchenhund on August 20, 2017, 04:29:50 amThe model being discussed is not a sampling oscilloscope. There were 4 different series of these mainframes:1. The 11400/11200 series are 20 MSamples/second and 10k with 10/9 bit resolution.2. The DSA series are up to 2 GSamples/second and 32k with 8 bit resolution.3. The 11300 series are 500 MHz MCP analog oscilloscopes with a lot of automatic amplitude and time measurement capability. These did not use a touch screen.These series all had at least dual independent timebase capability including dual delayed timebases.Except for the "low cost" 11200, the above all took the same improved 7000 series vertical amplifier plug-ins.4. The CSA/11800 series are sequential only sampling oscilloscopes operating at 200 kSamples/second and 8 bits with a bandwidth up to 40 or 50 GHz although the 20 GHz differential TDR/sampling head is probably the most interesting.These used the SD series sampling heads.

author: David Hess
author_rank: Super Contributor
timestamp: August 20, 2017, 07:13:35 am
content: Quote from: snoopy on August 20, 2017, 01:15:03 amI considered getting one for their math capability. These are one of the rare DSOs which can do real time vector network analysis using a step response input by differentiating the waveform and then displaying the magnitude and phase results from the FFT. Modern DSOs which can do this are pretty rare and expensive; LeCroy has a bunch which can but I am not sure about anybody else and of course anything new will cost as much as a car. Some of the old Tektronix TDS series can do it also.I do not know of anybody still using these in a production or business environment. Without service documentation they are difficult to maintain.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 21, 2017, 05:37:03 am
content: Quote from: David Hess on August 20, 2017, 07:04:12 am(emphasis mine)So you're saying the 11403 which is shown on the picture isn't a sampling scope then?Although you're right re the DSA and CSA of course.QuoteIndeed, also by now pretty much all of them will have reached the end of their service lifespan.

author: David Hess
author_rank: Super Contributor
timestamp: August 21, 2017, 05:51:12 am
content: Quote from: Wuerstchenhund on August 21, 2017, 05:37:03 amThat is right; the 11403A shown is not a sampling oscilloscope. Those vertical amplifier plug-ins are not sampling heads; they are an improved version of the 7000 series vertical amplifier plug-ins.If that is not enough, then a 3 GHz bandwidth is pitiful by sampling oscilloscope standards of 20 years before the 11403A was produced and the 11403A's horizontal timing specifications are not consistent with a sampling oscilloscope.

author: Hydron
author_rank: Super Contributor
timestamp: August 21, 2017, 07:25:36 am
content: The User Reference:http://w140.com/tek_11402A_11403_user_ref.pdfsuggests that it's running at 20MSamples/s for one channel, dropping to 5 and 2.5 for 2/3 channels respectively. Also talks about "Equivalent Time Sampling", and that in single shot mode you only get one sample per 50ns.Sorry, but it's not as exciting as it looks!

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 21, 2017, 08:57:52 am
content: Quote from: David Hess on August 21, 2017, 05:51:12 amWell, it doesn't look to be a true real-time scope either as 20 MSa/s is hardly enough to capture the 1Ghz BW of the 11A71 amplifier plugins on the photo.Quote from: Hydron on August 21, 2017, 07:25:36 amOk, so that would give it a real-time BW of roughly 8Mhz in single channel mode, 2Mhz in two channel mode and 1Mhz in 3 channel mode, the full BW seems to be available in ETS mode only => looks a lot like a sampling scope.

author: David Hess
author_rank: Super Contributor
timestamp: August 21, 2017, 01:21:33 pm
content: Quote from: Wuerstchenhund on August 21, 2017, 08:57:52 amIt is not a real time oscilloscope although the display is updated in real time for which 20 MSamples/second is plenty fast. Tektronix never claimed it was a real time oscilloscope and DSOs with sample rates to support a Nyquist frequency greater than their bandwidth were the exception back then.A 2230 is 100 MHz but only has a 20 MSample/second sampling rate but that does not make it a sampling oscilloscope. A 7854 is 400 MHz but only has a 500 kSample/second sampling rate and might be considered the predecessor to the 11400 series but it is not a sampling oscilloscope either.Quote from: Hydron on August 21, 2017, 07:25:36 amSo what distinguishes a sampling oscilloscope like the HP 54120B or Philips PM3340?1. The sampling gate width is much less than the sampling gate time constant so the input sampling capacitance never has time to charge to the input voltage. Another way to put this is that the sampling efficiency is below 1; usually it is a lot lower than 1.2. As a consequence of 1 above, the input is roughly integrated over the sampling gate width producing a non-linear frequency response which follows the sin(x)/x curve with a first null at the reciprocal of the sampling gate width. The familiar bandwidth = 0.35 / transition time rule does not apply.3. To take advantage of the extremely high bandwidth this produces, there are no amplification stages between the sampler and the input. (1) Usually there are no attenuation stages, delay lines, or other networks either. Even a length of transmission line would compromise the potential bandwidth and often does.(1) I know of one exception to this. High input impedance samplers include a *low* frequency buffer before the sampling gate to remove accumulated charge (2) from any input capacitance which could not otherwise be discharged by the high input impedance. High frequencies bypass this buffer. As far as I know, Tektronix was the only one to make high input impedance samplers.(2) I think the problem here was kickout from the sampling strobe charging the input capacitance causing the DC level to shift. The Tektronix 50 kilohm samplers (Tektronix S-3) did not need a low frequency buffer but their 1 megohm samplers (Tektronix S-5) had one.

author: snoopy
author_rank: Frequent Contributor
timestamp: August 21, 2017, 01:40:30 pm
content: I think the correct term is sub-sampling scope or equivalent time sampling which requires repetitive waveforms for equivalent sampling rates greater than the ADC sampling rate !

author: David Hess
author_rank: Super Contributor
timestamp: August 21, 2017, 02:03:45 pm
content: Quote from: snoopy on August 21, 2017, 01:40:30 pmThe correct term in place of what?There is nothing to preclude DSOs (digital *storage* oscilloscopes) with real time sampling from using equivalent time sampling and many do to achieve even higher sampling rates so the term equivalent time sampling is ambiguous in distinguishing them.

author: Johnny10
author_rank: Frequent Contributor
timestamp: August 21, 2017, 02:57:22 pm
content: I use the DSA602 and 602A as my everyday scopes.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 21, 2017, 03:34:02 pm
content: Quote from: David Hess on August 21, 2017, 01:21:33 pmA digital scope is either a real-time scope (aquires the waveform in real-time) or a sampling scope (i.e. it acquires the waveform over multiple acquisition passes).QuoteBoth the 2230 and the 7854 are are analog/digital combi-scopes which both reach their analog BW in repetitivesamplingor analog mode only. You're right that none of them are true sampling scopes as they are combi scopes with an analog and a digital mode.QuoteBack in the old days, Tek used to define1a sampling scope as a scope that put the sampler in front of the amplifiers and a DSO as a scope that has amplifiers in front of the sampling stage. But this was never an universally accepted definition and wasn't even correct as not all sampling scopes followed Tek's definition (i.e. LeCroy WaveExpert and I believe also the Agilent/Keysight DCA-J/-X). HP also had some sampling scopes (i.e. the 54501A) which didn't follow Tek's rule as well.Today, a sampling scope is generally considered a fully digital scope that acquires its waveform over subsequent acquisitions to reach its full analog BW. It doesn't matter what sampling technique is used (random or sequential), or how it is actually implemented.1http://www.tek.com/sites/tek.com/files/media/media/resources/Sampling%20Oscilloscope%20Techniques.pdf

author: David Hess
author_rank: Super Contributor
timestamp: August 21, 2017, 08:08:37 pm
content: Quote from: Wuerstchenhund on August 21, 2017, 03:34:02 pmGreat! So depending on the time/div setting and the input frequency content or bandwidth limiting, a DSO could be either. Or maybe all of those DSOs which can operate either way are a myth. That sure unambiguously simplifies things.QuoteThe analog capability of these oscilloscope is irrelevant to the discussion. Why bring it up?And you are flat out wrong. Neither of these oscilloscope are bandwidth limited below Nyquist. The bandwidth for both is independent of sample rate. This is easy to demonstrate by making an RMS noise measurement at different sample rates; lower sample rates which cause aliasing do not change the measured amplitude because the input bandwidth does not change. The same measurement made of a sine wave or any other signal will produce the same result. Some DSOs take advantage of this for their external calibration.QuoteIf the marketing departments of other companies want to confuse the issue, that is up to them. One reason they did so is because sampling oscilloscopes were traditionally difficult to use which is why the Tektronix 7S14/5S14 were designed with a built in delay line which is the primary thing limiting their performance. The delay line was either external or optionally built into later Tektronix sampling oscilloscopes. The Philips PM3340 has a delay line as well limiting its bandwidth to 2 GHz but making it much easier to use.The HP 54501A is just another digital storage oscilloscope with analog triggering, a bandwidth of 100 MHz, and a sample rate of 10 MSamples/second making it comparable to a 2230 or the 11403A being discussed except for the exceptional bandwidth of the 11403A. The comparison with the 11403A is apt because both HP and Tektronix fell into the "one big knob" user interface trap at that time. In the future, one big knob will control everything!The definition that Tektronix used has the virtue of being less confusing but even they later limited it to the product descriptions instead of the product names leading to things like "communications signal analyser", "digital signal analyser", and "digitizing oscilloscope" which could mean anything including a 7104 with a digital camera or a scan converter.So what distinguishes the performance of a sampling oscilloscope from your examples? Overload recovery time is one. Sampling oscilloscope have no overload recovery time which is very useful or even indispensable for some measurements. If I want the best overload recovery time, then I want a sampling oscilloscope no matter what they are calling it today. Picotech makes some and they even call themsampling oscilloscopes. Everything else they make is unambiguously real time but some of their Nyquist bandwidths are not much higher than their input bandwidths; I much prefer ETS support when that is the case.

author: shteii01
author_rank: Frequent Contributor
timestamp: August 22, 2017, 12:29:28 am
content: I have 11403 (not A) with 300 MHz plugin for personal use. I have not done much with mine simply because of being busy.Interesting side note. I know from Tek Wiki about 1989 date. But I also looked at the Tek catalogs and 11403 does not show in 1989... If I recall correctly it first shows in 1991 or '92.

author: edavid
author_rank: Super Contributor
timestamp: August 22, 2017, 02:06:37 am
content: Quote from: David Hess on August 21, 2017, 05:51:12 amExcept for the 11A81 3GHz "presampler" vertical plugin.(Does anyone know the presampling rate?)

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 22, 2017, 02:22:47 am
content: Hi,I have a couple of DSA602A in my collection. They were probably the peak of this series of scopes.Here is a screen shot:At some point I wrote a C program to convert the image format to TIFF.The 'A' version had a floppy, the non A didn't.There were four 500M s/s digitizer, that gave you up to 2Gs/s with interleaving on a signal channel. Memory depth was 32k samples.I also has 11801 with SD24 sampling heads. This is 20 GHz bandwidth, but 20 M sps.There were later versions of the 11801 with color displays etc.Regards,Jay_Diddy_B

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 22, 2017, 02:35:32 pm
content: Quote from: David Hess on August 21, 2017, 08:08:37 pmNope, that has nothing to do with settings. If a scope's max sample rate is sufficient to fully capture a signal at its rated BW in a single acquisition then it'sa real-time scope, if the max sample rate is insufficient then it's a sampling scope.QuoteBecause these scopes are not fully digital scopes, they are combi-scopes, and on combi-scopes the digital part is usually kept simple compared to a contemporary digital scope. BTW, these were your examples, not mine.QuoteYes, for something simple like noise measurement you're right, but then you don't need a scope for that. But that doesn't change the fact than neither of these boat anchors can (digitally) capture a true waveform of a signal at BW limit in a single acquisition. And for a scope, this is what counts.QuoteIt's not confusing the issue, and it's not even driven by marketing.This is whatKeysight has to say:Oscilloscopes fall into two groups, real-time oscilloscopes and sampling oscilloscopes (also called equivalent-time oscilloscopes) and it is important to understand the difference between the two types. Real-time oscilloscopes digitize a signal in real-time. Imagine a repetitive AC signal - the real-time oscilloscope acts like a camera, taking a series of frames of the signal during each cycle. The amount of frames the real-time oscilloscope captures depends upon the bandwidth, memory depth, and other attributes that we will soon discuss. A sampling oscilloscope, on the other hand, takes only one shot of the signal per cycle. By repeating this one shot, but at slightly different time frames, the sampling oscilloscope can reconstruct the signal with a high degree of accuracy.I know that it's difficult to understand if you only know Tek because that's what you grew up with but they don't dictate the rules. Tek's definition back then was just that, something used by Tek based on the products they had at that time. Others however used a wider definition and for what it's worth this is what has been well established in the T&M field.QuoteFunny you mention PicoScope, as it seems they, too, disagree with your definition ofSampling Scope:https://www.picotech.com/download/manuals/picoscope-9000-series-questions-and-answers.pdf:A sampling oscilloscope is a special type of oscilloscope that uses a technique called sequential time sampling.This type of sampling is best suited to repetitive waveforms or those that are derived from a regular clock, such as serial data streams, clock waveforms and pulses in digital circuits, semiconductor test patterns, and amplifier pulse-response and rise-time tests. Signals like these tend to have very high bandwidths or high data rates. A sampling scope captures just one sample from one trigger event, typically a single cycle of the waveform or clock, and then repeats the process over a large number of cycles, varying the timing of the sample by a small increment from one sample to the next. The resulting collection of samples is then assembled into a picture of a typical cycle.The advantage of a sampling scope is that even with input signals in the gigahertz range, the output of the sampler is at a much lower frequency, typically in the audio frequency band. This allows high-fidelity, low-frequency amplifiers and ADCs to be used to capture the signal. For example, the PicoScope 9300 Series can capture waveforms up to 20 GHz with high precision (16-bit resolution before scaling and processing). A real-time DSO that could capture a single cycle of the same 20 GHz waveform would be prohibitively expensive. For example the 20 GHz Agilent DSOX92004A, with a real-time sampling rate of 80 GS/s, has a base price of $177,000 — almost 12 times the price of the PicoScope 9301 while yielding only 4 samples per cycle. The PicoScope 9300 Series, sampling at an effective rate of 15 THz, would yield 750 samples per cycle of the same waveform.A further benefit is that every sample point in the sequential sampling process is timed from the trigger event, and therefore from the original signal, rather than derived from an internal oscillator. Sampling jitter is therefore vastly reduced compared to the singletrigger, clock-derived sampling of the real-time DSO counterpart.As I said, I understand where you're coming from but there's no point to fixate of a some 30 years old definition by a single manufacturer while constantly refering to ancient kit that has long been obsolete when the rest of the world has moved on.

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: August 22, 2017, 09:09:47 pm
content: I regularly use CSA803A with SD-30 sampling head (end of 1980's - beginning of 1990's tech) and I have to say that 11800/CSA803 has the worst ever user interface I have experienced - hands down. It's so experimental, random, confusing and eclectic.Many operations include pressing a dedicated function button (often twice or more), then using the touch screen - or rather un-touch as it activates on finger withdrawal rather than touch (it does not detect push) and then rotating one of the large knobs. It's just awful. And yes, there are popup menus that blend with main screen and don't look like pop-up menus.When i have tried to use it for the first time without warning, I spent about 30 minutes trying to modify timebase scale (what else do you do with the scope?) and in the end have given up and had to read the manual. It turned out you had to press one of the function buttons twice to get to the right touchscreen and knob roll.User interfaces with state are evil - you need to concentrate on what the screen is telling you and you can't just engage muscle memory to get you to the right place.Oh, and the required channel is turned on/off by a tiny button on the head that has no tactile feedback, beep or any other way of knowing the state. And yes, active channel has a dim blinking LED when it's on. And yes, channel traces randomly change colour - the first one you happen to turn on is green, the second is red - irrespective of their physical location.And it looks even worse than it feels.Other than that it's awesome - its sampling technology is genius, frontend hybrids are beautifully laid out and you can get a 20GHz dual channel capability for $500. You often get an instrument that has been hardly used - I guess due to reasons above.Leo

author: snoopy
author_rank: Frequent Contributor
timestamp: August 23, 2017, 07:29:15 am
content: Quote from: David Hess on August 21, 2017, 02:03:45 pmHi DavidI have a Tek TDS784 scope with a max ADC sampling rate of 4Gs/s. Anything above that it jumps into equivalent time sampling upto an effective sampling rate of 250 Gs/s. I'm fine with thatAs long as the signal is repetitive then equivalent time works perfectlycheers

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: August 23, 2017, 08:03:09 am
content: I have posted few 11800/CSA803A frontend photos elsewhere but they are so beautiful they need to be here too. They don't care how they are called.Leo2 channel 20GHz sampling head1 channel 40GHz sampling hybridAmplifier/offset/gain hybrid

author: snoopy
author_rank: Frequent Contributor
timestamp: August 23, 2017, 08:17:22 am
content: Quote from: Wuerstchenhund on August 22, 2017, 02:35:32 pmI'm not sure if the world has moved on that much but according to Teks current lineup this 80GHz scope only has a 300kS/S sampling rate ! Perhaps that is a misprint but it does say "sampling scope" !Quotehttp://www.tek.com/oscilloscope/dsa8300-sampling-oscilloscope

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 23, 2017, 11:20:13 am
content: Quote from: snoopy on August 23, 2017, 08:17:22 amWell, it is a sampling scope (i.e. a scope that uses multiple acquisitions to capture a waveform at analog BW), so why should it be a misprint?The DSA8300 is basically a rehash of the DSA8000, which is based on the old TDS7000, so it's not exactly a new scope.The real advantage of these scopes is in their low price compared to a real-time scope with the same BW.

author: David Hess
author_rank: Super Contributor
timestamp: August 27, 2017, 04:44:50 am
content: Quote from: edavid on August 22, 2017, 02:06:37 amI was not aware of the details of this plug-in although I knew it existed. It is pretty cool but the specifications given in the 1993 catalog on page 79 are not consistent with a sampling plug-in.What happened is that the mainframe's interface connector cannot handle a 3 GHz bandwidth (1) so Tektronix implemented the attenuators, vertical amplifier, and a sample and hold in the plug-in. It is not a sampling input in the sense of a sampling oscilloscope and this can be seen in the specifications which show a 10ns overdrive recovery time and a 25 volt peak maximum input voltage.The older 7854 with the 7T11A sampling timebase works in the same way with the mainframe's digitizer slaved to the sampling plug-in so Tektronix was aware of this possibility.QuoteI could not find it in the sparse to non-existant available documentation for the CSA404, 11403A, and 11A81. It should be only limited by the sampling rate of the plug-in itself because the bandwidth between it and the mainframe is 1 GHz leaving plenty of time for settling between samples. That would make it 20 MS/s maximum just like any other vertical plug-in.(1) It was a pretty big deal when Tektronix extended the 7000 series interface to 1 GHz in the 7104 and there were trade articles written at the time about how they did it.Quote from: Jay_Diddy_B on August 22, 2017, 02:22:47 amThe 11K and SD specifications all say 200 kS/s maximum. I think the chief limit in these single sampling gate designs is the operating life of the avalanche pulse generator.Quote from: Wuerstchenhund on August 22, 2017, 02:35:32 pmIt is confusing and here is why. Sampling oscilloscopes in the sense that I am using the term have three features which are not found in other oscilloscopes:1. They have zero overload recovery time. A sampling bridge does not care about what is going on during the time that the sampling gate is not open. A practical application of this is measuring settling time to high accuracy which is somewhere between difficult to impossible with a normal oscilloscope which otherwise has sufficient bandwidth.2. They use a sampling efficiency much lower than 100% to exceed the RC bandwidth limitation of a sample or track and hold which uses a sampling gate time greater than its RC time constant to allow full settling. This results in a huge increase in bandwidth.3. 2 above produces a non-linear sin(x)/x frequency response do to integration during the sampling gate time. The effective sampling gate width can be measured by looking for the null in the response.Both 1 and 2 above lead to sampling oscilloscopes not using linear elements like amplifiers or delay lines before the sampler. Either would significantly lower the achievable bandwidth and the former would destroy the overload recovery capability.QuoteAnd in the very first sentence, Picoscope gets it wrong. There is nothing about a sampling oscilloscope which requires sequential sampling. Indeed, random sampling in a sampling oscilloscope allows viewing the triggering waveform without the use of a delay line or pretrigger. The only reason they were not more common is that most applications could live with these limitations.QuoteThe point is that your definition confuses two different classes of oscilloscope which have distinct properties. If there is a better and less ambiguous term for sampling oscilloscopes in the older sense, then let us know.Quote from: Leo Bodnar on August 23, 2017, 08:03:09 amNote that the coaxial line on the top carries the sampling strobe from the mainframe to the sampling gates and the two coaxial lines on the bottom carry the divided sampling strobes back into the mainframe for timing measurement. This is required to achieve high horizontal timing accuracy. None of the coaxial lines carry the sampled signal which is low bandwidth after the sampling gates.Quote from: Wuerstchenhund on August 23, 2017, 11:20:13 amI like them because they are immune to overload and have a predictable frequency response allowing them to be used to calibrate the transient response of other instruments. It is even possible to calibrate the transient response of a sampling oscilloscope without an external reference although it takes 3 sampling oscilloscopes to do this. Maybe I should have included this in my list of features above.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: August 27, 2017, 08:22:12 am
content: Would add that while RTS scope with ETS feature do not tick all the boxes mentioned it still helps with 2 things:- no interpolation related artefacts- very high horizontal accuracyWeird that many cheap DSOs are dropping support for ETS. Failure to educate end-user of advantages or just cost-cutting? I suppose it needs better trigger system than just RTS / lowish sample rate where users in general seem to expect no better accuracy than +-sample_interval.

author: RoGeorge
author_rank: Super Contributor
timestamp: August 27, 2017, 08:40:06 am
content: Quote from: Leo Bodnar on August 23, 2017, 08:03:09 amBeautiful pics, thank you!

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: August 27, 2017, 08:44:04 am
content: Quote from: David Hess on August 27, 2017, 04:44:50 amNo. The top rigid line is TDR trigger pulse. It triggers both channels but channel 2 has analogue voltage-controlled delay inserted in line with its trigger.The middle one is the strobe drive for sampling pulse generator. Both channels are sampled simultaneously.Bottom rigid line is the strobe sense for the sampling pulser. It provides feedback from the output of SRD back to the scope sense strobe driver board. This feedback has not been used in S-xx series heads.You probably got confused because Tek uses the same carrier PCB for SD-22/SD-24/SD-26 even though only SD-24 needs TDR section. It is a low volume product so each head seem to have had some uniqueness to it. One of my SD-26 heads has provision for loop-through on the sampling hybrid as if it was expected to be used in SD-20.QuoteThat is true. The sampled signal outputs travel over two regular pins just like other control voltages and digital data. It's a low impedance low BW signal so I can see why there was a temptation not to add two more coaxial lines.However as soon as they enter the scope they are immediately fed into the separate coaxial cables.Head extender also uses two coax lines for sampled signals. Note two extra coax cables that carry sampled signal.I have attached a sampling head output for a pulse with 40ps risetime.CSA8000 head extender before converting to operate on CSA803A:SD-26 sampled signal output for a 40ps risetime pulse. Sampling rate is about 115ksps:

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: August 27, 2017, 09:53:14 am
content: There was a relevant post on TekScopes group about 14000 series from someone at Tek. I cross-post for those who are not subscribed:https://groups.yahoo.com/neo/groups/TekScopes/conversations/messages/96244John Addis later joins in the discussionwhich this margin is too small to containQuote

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 27, 2017, 02:14:39 pm
content: Quote from: Leo Bodnar on August 27, 2017, 09:53:14 amUnfortunately this wasn't just for the first couple of generations, Tek's overconfidence in its products continued for a very long time, and frankly I'm not sure it's even over yet. The new MDO5 Series, while having some interesting features, looks like another product without a target market.Tek always treated a DSO as a replacement of an analog scope, without recognizing the power that lies in digitalization, and I'm not sure they ever got it. And even when it comes to making DSOs that behave like analog scopes Tek was left behind by HPAK and its MegaZoom-based scopes.That's pretty much why Tek's DSO range has been dominated by underwhelming product after product ever since, which is a shame.

author: snoopy
author_rank: Frequent Contributor
timestamp: August 28, 2017, 02:03:05 am
content: Quote from: Wuerstchenhund on August 27, 2017, 02:14:39 pmThat is simply not true. The older Tek TDS744A DSO catches glitches just as well if not better than a later Agilent MSO6104 scope with Megazoom !! Tektronix were way ahead of their time with their patented digital phosphor technology !

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 28, 2017, 08:09:21 am
content: Quote from: snoopy on August 28, 2017, 02:03:05 amAnd you gather that from a single Youtube video (where the narrator even says towards the end that the Agilent is the better scope)?QuoteNo, they weren't 'way ahead of their time'. For a start, try to do some math on a signal when the TDS744A is in InstaVu mode. Oops, you can't, because InstaVu works by data reduction (it drops the sample rate and the sample memory) and writing the data directly into the video buffer. Which is why a lot of the scope's features (Auto Trigger, Zoom, limit testing, FastFrame, Math, X/Y, Envelope mode, Average mode, HiRes mode, no single-shot capture, and no interpolation in real-time mode) are unavailable in InstaVu. Needless to say that HPAK's MegaZoom doesn't suffer from these limitations.Tek's idea was to re-create the display of an analog scope (because their basic assumption was that DSOs should just be a modern form of analog scopes), and that's exactly what InstaVu does. You get high waveform rates at the price of being able to do nothing with the sampled data other than look at it. If you want to do something with the data (i.e. use the very basic set of math and analysis tools the TDS offers) then you have to go back to the TDS' 50 updates/s normal acquisition mode.HP on the other side didn't believe that digital scopes should replicate analog scopes, and didn't give up on the advantage of digital signal processing just for high waveform rates (and actually managed to deliver both as an 'always on' solution which back in 1995 was quite a feat, even more so considering that the 54600 Series were on the lower end of the price scale). HP knoew that engineers would want to make use of the benefits of digitalization, but back then a standard scope like the 54600 would still often be used in places where it replaced an analog scope, and where the high waveform rate was useful.LeCroy did go a different way than Tek and HP, not offering high update rates but instead providing a very sophisticated trigger suite which would allow to trigger and capture pretty much any signal devication on its first occurrance, after which it could be analyzed further with the advanced math/statistics and analysis tools their scopes offered. LeCroy didn't build entry-level scopes (they were always bought in from other vendors like Iwatsu), and they figured that their advanced toolsets will more than compensate for the lack of superfast waveform rates.Looking at the market some 23 years later, it turned out that HPAK and LeCroy were right in their assumptions. Keysight is the largest T&M vendor, and of the three big names sells the highest number of scopes. LeCroy is doesn't have the numbers as they can't really compete in the entry-level (for which they offer rebadged versions of old Siglent scopes) but they pretty much lead in the high-end segment (where for some products there simply is no other vendor). Tek however has been on a constant decline pretty much since the end of the analog scope era, and have been for a reason. It would be nice if they finally woke up and smelled the coffee, and started turning the ship around, but all signs indicate that after the separation from Danaher they just continue in their old ways.

author: snoopy
author_rank: Frequent Contributor
timestamp: August 28, 2017, 09:22:44 am
content: Quote from: Wuerstchenhund on August 28, 2017, 08:09:21 amInstavu and DPO is not an underwhelming product enhancement by any stretch of the imagination. No other scope at the time had the ability to catch glitches at the same rate as these Tek scopes. I have measured the trigger rate on these scopes and yes they do deliver on the vendors claims of up to nearly 400,000 waveforms per second capture rate.And yes the sample memory is dropped and yet it still catches the glitches that other scopes miss. And yes a lot of features are disabled with Instavu mode enabled but you are missing the point of this feature. You enable this feature to determine whether or not your circuit has glitches and you don't want to wait days glued to the screen to find out. Who cares about the measurements if you are trying to chase down an intermittent and illusive problem in the design missed by other scopes ! Once you have determined the nature of the problem then you can setup a trigger to catch the glitch in action in normal DSO mode. Also that Megazoom feature on Agilents scopes has that pesky limitation of only providing measurements on the screen data and no more .And comparing a 1995 scope with a 2015 scope that costs megabucks is not a fair comparison when you can pick the Tek scopes up pretty cheap in comparison to this 2015 Agilent model !

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 28, 2017, 10:26:53 am
content: Quote from: snoopy on August 28, 2017, 09:22:44 amThat's nonsense, a scope that uses dedicated triggers will if setup correctly find always a glitch on its first occurrrence, as it doesn't have to rely on failure-prone human eyes to identify the glitch.Also, seeing all these glitches fly by in InstaVu mode only shows you that there are glitches, which is great if you're the 'stare-on-the-screen-until-you-see-something-abnormal' type of guy, but usually finding out that there are glitches is only 1/3rd of the work, the other two are analyzing the anomaly (to find out where in your UUT the problem is) and then fixing it.Step 2 already fails in InstaVu so you have to re-acquire in normal mode, which on the TDS700A is dog slow (Tek specifies an update rate of 50 per second). And if you can't trigger on the anomaly because your TDS700A lacks the advanced triggers then you have to rely on the 50 updates/s and the resulting large blind time to capture the glitch so you can do some analysis of it. GreatQuoteNo, it doesn'tThat's just your imagination. And like an analog scope, the TDS isn't really 'catching' glitches, all it does is displaying them. Same as an analog scope.QuoteSeriously, if your glitch hunting technique is limited to looking at a screen until you see a glitch then either you're using poor equipment or you have a lot to learn about how to use a scope properly. Especially with very rarely occurring glitches (i.e. say every 10 minutes) there's a very good chance you miss the glitch, because your eyes get fatigued from staring at the screen, you blink, or become otherwise distracted. That's why better scopes come with a set of advanced triggers so you can setup the scope and do something else while the scope will 'see', capture and if necessary process (i.e. build a histogram, which can be tremendously helpful in finding out what's causing the glitch) the data and present you with the results on your return.The reality is that InstaVu is unlikely to show you any glitches that you can't see on a similar old MegaZoom scope, and neither of those can capture glitches better than a scope using a suitable trigger. If you think otherwise you're just deluding yourself.QuoteWTF are you talking about? What comparison?

author: snoopy
author_rank: Frequent Contributor
timestamp: August 28, 2017, 11:06:31 am
content: Quote from: Wuerstchenhund on August 28, 2017, 10:26:53 amWell if you can't identify what the glitch is then how can you ever setup the trigger to catch them ? Just try every possible permutation or combination of triggers ? A normal scope may never show the glitches for days and one may assume that there is nothing wrong with the circuit at hand. Later Tek scopes had the ability to set off an audible alert and freeze the display when a glitch occurred ! You talk like Instavu has no value at all in diagnosing a problem with a circuit !! Perhaps you've never done any fault finding and this feature would not be of any use to you ?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 28, 2017, 01:12:29 pm
content: Quote from: snoopy on August 28, 2017, 11:06:31 amNo, of course you're not trying every permutation. On older scopes (like some of the ones from the mid-'90s) you just setup an exclusion trigger with the parameters of the signal, and wait for the glitch to appear. Chain it with statistics and you can get a nice histogram of when each glitch occurred, which in a complex circuit should usually gives you an idea to narrow the cause of the glitch down.QuoteYes, for glitches that have periods of 10's of minutes or even hours, in which case sitting in front of an InstaVu screen would be equally silly because all it does is showing that there's a glitch, and that only if you happen to see it (sometimes glitches can even be small enough for them to remain unrecognized by the operator), and if you see it you then have to re-capture again in snail mode and hope your slow Tek scope will capture it with its now vastly extended blind time.Also, in your rabid praise of InstaVu you completely ignore that even this mode has a blind time, and is likely to miss the occurrence of a glitch. Which means that even if you spend half an hour looking at your signal in InstaVu without seeing a glitch doesn't mean there is none, it just means you can't say with certainty that there are glitches.The only way to be sure are advanced triggers.QuoteYes, in DPO mode, which is just a slightly improved version of InstaVu.QuoteI never said InstaVu has no value, I said it provides the same value like an analog scope which even back in 1995 was pretty limited. It's all great that InstaVu and DPO can achieve high waveform rates but the point you (and Tek, obviously) miss is that for a digital scope just emulating an analog scope isn't enough.Ever wondered why even modern high-end scopes often only have waveform update rates in the thousands or 10k's per second? Exactly, because high update rates become pretty meaningless when you have a set of advanced triggers and analysis functions that can find pretty much any problem in any signal you want. Even on non-repetitive signals (try to find glitches on a non-repetitive signal with InstaVu, good luck!).The point I was making (and on which you jumped off with your InstaVu fanboisim) is the same as the one the former Tek guyJohn AddisSteve Ditter was making, which is that Tek has been (and still is) living in their own world without considering what the competition does and what customers actually want. Again, if the aim was to make a digital scope that feels and can be used exactly like an analog scope then Tek was indeed very successful. But that's not what customers wanted, which was taking advantage of the possibilities that digitizing an analog signal brings, and which have been offered by HPAK and especially LeCroy (which for DSOs is pretty much what Tek has been for analog scopes). And this mindset can still be seen in Tek's latest products, which I find very unfortunate as I'd really like to see them stepping up and becoming a noteworthy competitor once again.

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: August 28, 2017, 01:30:22 pm
content: Quote from: David Hess on August 27, 2017, 04:44:50 amI came to conclusion that SD sampler heads don't use avalanche effect generators.They do have SRD and clipping line sampling setup carried over from S series but SRD is excited by complimentary BJT pair in an arrangement that looks like a multivibrator.I am not certain if SRD has stress limit when it reverse-conducts but it is certainly not well thermally connected to anything - it just hangs on its beam leads between two capacitors.Perhaps, the sampling rate limit is enforced by maximum rate of TDR pulsers or some recovery processes in the mainframe. 11700 is so complex, it's hard to say for certain.Leo

author: edavid
author_rank: Super Contributor
timestamp: August 28, 2017, 02:43:40 pm
content: Quote from: Wuerstchenhund on August 28, 2017, 01:12:29 pmYou misread that, it's Steve Ditter who is the 11K series hater. John Addis is more positive.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 28, 2017, 03:15:55 pm
content: Quote from: edavid on August 28, 2017, 02:43:40 pmMy bad, thanks for the correction. Posting updated.

author: snoopy
author_rank: Frequent Contributor
timestamp: August 31, 2017, 01:30:13 pm
content: Quote from: Wuerstchenhund on August 28, 2017, 01:12:29 pmYes it is blind for small amount of time but it all comes down to probabilities. Even if a glitch has an average rate of one per hour you just set Instavu mode with infinite persistence so you are likely to capture the glitch in an hours time or there abouts without having to stare at the screen to wait for it. Whereas your traditional 1% acquisition time scope would take 100 hours on average at the very least to reproduce the glitch ! Also with Instavu mode switched on, measurement are still available as well so not everything is disabled. I think these scopes were way ahead of the competition at the timecheers

author: smaultre
author_rank: Regular Contributor
timestamp: June 16, 2024, 07:42:22 am
content: Hello guys, is it actual to buy nowdays HP 54120B with the 54124A, which could go up to 50Ghz?Or Tek stuff like 11700 or 8000 series are better?I would like to measure up 40-50GHz division.

author: tggzzz
author_rank: Super Contributor
timestamp: June 16, 2024, 08:28:49 am
content: Quote from: Wuerstchenhund on August 20, 2017, 04:29:50 amPhilips had the PM3400 1.7GHz "11/12 bit" sampling scope back in1971. It could resolve ~200µV in 3V, hence "11/12 bit"IIRC there are three transistors with fTexceeding 500MHz; the rest are BC107 class with an fTaround 200MHz.https://www.radiomuseum.org/r/philips_sampling_oscilloscope_pm3400.htmlhttps://www.eevblog.com/forum/testgear/tektronix-scope-with-sampling-plug-in/msg468702/#msg468702QuoteSome of them are prized by their owners, e.g. for TDR assessments of PCB tracks+components, or examining the last 0.1% of an amplifier's risetime.General purpose? No. But that's not necessarily the point.

author: David Hess
author_rank: Super Contributor
timestamp: June 16, 2024, 02:57:51 pm
content: Quote from: tggzzz on June 16, 2024, 08:28:49 amSampling oscilloscope are almost uniquely useful for doing transient response calibration.The input stage of a sampling oscilloscope is immune to overload, so they are also very good for making settling time measurements at high sensitivities that other oscilloscopes simply cannot do.

author: tggzzz
author_rank: Super Contributor
timestamp: June 16, 2024, 03:09:43 pm
content: Quote from: David Hess on June 16, 2024, 02:57:51 pmJust so.Unfortunately that doesn't stop some salesmen claiming otherwise.https://www.eevblog.com/forum/testgear/choosing-between-entry-level-12-bit-dsos/msg5433389/#msg5433389But advances in ADC and front endsarecontinuing to eroding that advantage.

author: David Hess
author_rank: Super Contributor
timestamp: June 16, 2024, 06:00:21 pm
content: Quote from: tggzzz on June 16, 2024, 03:09:43 pmADCs and front ends have been trying to solve the overload problem for decades, (1) and greater sensitivity makes it worse. It along with the settling time problem are hard problems, which a sampling input completely solves. Jim Williams wrote about these two problems, which are linked. He spent a lot of effort designing a circuit to prevent oscilloscope overload and then used a sampling oscilloscope to verify its performance.Oscilloscopes that have input offset controls may make an attempt to solve this. The Tektronix 7A13 differential comparator uses feedback to clamp the input, so does better than most oscilloscope inputs. I think this was also a feature of the differential comparator Tektronix made for their 11k series of mainframe oscilloscopes, which includes DSOs.Jim Williams talked about the issues here:https://www.analog.com/media/en/technical-documentation/application-notes/an47fa.pdf(1) Not really - hardly anybody cares about overload performance.

author: tggzzz
author_rank: Super Contributor
timestamp: June 16, 2024, 07:18:48 pm
content: Quote from: David Hess on June 16, 2024, 06:00:21 pmYes.The improvements in ADC and front ends appears to be just an increased number of bits (effective or otherwise) at high sampling rates. That enablessoftware"select rectangle and zoom in" functions, i.e. withouthardwarefiddling with large DC offsets.