Author Topic: Do You still use analog oscilloscopes in 2019?  (Read 9269 times)

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Offline David Hess

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #125 on: August 06, 2019, 04:53:19 am »
Reading this topic reminded me of a quote that I recall but can't find it again, I recall it was Chuck Yeager at an airshow - a P51 was being compared to a modern jet and someone was extolling the virtues of the P51 - his reply was to the effect of - don't get sentimental - old gear is fine for restoration - but almost always the most modern is the best - something like don't bring a knife to a gun fight.

I think the "almost always" is the key here. The strategists inebriated with the newfangled technology of radar seeking fitted their F4 Phantoms with AIM-7s only and removed the ancient machine gun tech. As per McNamara's words: “…being equipped with a gun is as archaic as warfare with a bow and arrow.”

This is also from a guy (Yeager) so full of himself that he could not be bothered to check his fuel state resulting in a research F-105 crashed into the desert while joy riding.
 
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Offline David Hess

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #126 on: August 06, 2019, 05:40:18 am »
When talking about menus and such, the interface of older technology tends to be much more accessible - after all, the options are entirely enclosed in the front panel and not hidden under tabs, drawers, doors, etc. (the physical equivalent of soft menus).

The problem is how to aggregate the plethora of new options in such small panel. Sure, a Tek 555 sized gear could probably have enough real state to accommodate all the options in a DS1054Z.

That's a significant issue, of course.

It is not an issue at all; modern DSO interfaces (and other test instruments) are just poorly designed.

The issue with limited space for hard controls is *which* controls do you include and they pick based on marketing or maybe a dart board rather than usability.

Two things I would like to see are number pads and dual soft encoders; the later would be a real improvement and wide format displays make it even more practical.  One thing I really hate are "stylized" buttons.

Dual beam and dual time base with delayed sweep would be easy enough to implement in a DSO. Not cheap, but certainly easy. People instead make do with really deep memory.

Implementation would be close to free as far as the hardware is concerned.  It would be especially useful in situations where even a large record length is not sufficient to maintain the highest sample rate or where processing power is not sufficient.  Dual decimators would allow capturing a maximum sample rate section of an existing waveform whether the record length is sufficient or not.  And it would not even require an extra trigger circuit unless the underappreciated trigger after delay feature is supported.

But I agree with you; people make do with deeper memory and that covers most use cases although it yields lower performance.

Dual beam is implemented simply by having a single ADC for every input channel. It only costs more and requires more memory bandwidth.

Multiple digitizers is the expensive way.  Early DSOs chopped the signals in the analog domain to support more than one channel and it worked fine.  That did not scale with sample rate so chopping during decimation became the standard and is still used except in "real time" DSOs that have a completely separate digitizer per channel.

Quote
You definitely don't want to play around with altering the ADC clock rate. Any mechanism to do that would add jitter, and that's a no no.

Only very early DSOs attempted to do it that way.  Very early on, the digitizer was run at its maximum sample rate and the output was decimated.

Quote
You could implement a delayed sweep by simply not clocking data into memory until the relevant number of samples after the trigger occurred, but that would mean you couldn't see the pre-trigger data thus losing a major advantage of digitising scopes. Avoiding that requires storing all the incoming samples in case a trigger arrives later, and that might mean a deep memory. But memory is cheap, so that's a good tradeoff.

You could do it that way but nobody did except for some of the first DSOs.  The difference between a normal sweep and a delayed sweep is simply whether the trigger is delayed and that only requires a counter.  The pretrigger data is preserved either way.  If this were not the case, then you could not set the trigger position in delayed sweep mode.

Quote
Early digitising scopes used a CCD to sample and store the waveform, typically limited to the 1024 samples shown on a screen. Such shallow memory was a necessary evil, but is of limited use and should be avoided.

Some early digitizing scopes worked that way and their record lengths eventually reached 120 kSamples.  They were competitive up to about 2000 where high real time sample rates were important.

It takes more than just an ADC per input to implement dual beam functionality. For each ADC there should be an independent time base and triggering circuitry. A dual beam scope is really two separate scopes that share only the phosphor on the CRT. Well, and power supplies I suppos.

Different time bases are implemented with decimation on the digital side.  With digital triggering, the cost of the extra hardware is tiny.

Most dual beam oscilloscopes only had one set of horizontal deflection plates so only supported a single sweep or delayed sweep.  Completely independent beam instruments like the Tektronix 556 and 7844 were the exception rather than the rule.
 

Offline David Hess

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #127 on: August 06, 2019, 05:57:53 am »
With delayed sweep you see two traces for each input: The main trace with the A timebase, and an expanded trace running at the faster B timebase. The portion displayed by the B timebase trace is intensified on the A timebase trace which gives the context. Note that the dual time base feature  exists for single as well as dual beam scopes.

For those of us that grew up with dual time base scopes, it is second nature to pull the time/div knob and rotate it clockwise to get the faster B sweep speed.

It is worth mentioning *why* delayed timebases existed.  It was for more than a magnified view.

Delayed timebases implement "slideback" measurements which are more accurate than counting divisions on the CRT.  That is why the delay control either has calibrated markings or a readout of delay time.  If you align a waveform feature on the graticule and then align a second waveform feature on the graticule, then the difference in the delay control settings is the duration between the waveform features.  This measurement has higher accuracy because it does not rely on CRT calibration or linearity.  Some later instruments supported dual *delta* delay timebases which displayed two separate delayed sweeps allowing the direct readout of the time or frequency.

DSOs never really needed delayed sweep for measurements so it eventually became rare.  They could use cursors or automatic measurements.
 
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Offline Mr. Scram

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #128 on: August 06, 2019, 06:38:22 am »
This thread has a scent of OP needing us to validate his use of analogue oscilloscopes. It seems likely the population on this forum isn't quite representative and the CRO crowd is over-represented just like vintage equipment is over-represented in the TEA thread.  The truth is that CROs are still around and still useful. Another truth is that they're on the way out. None of the serious players produce analogue oscilloscopes any more. Although it's possible the world is itching for one and these annoying manufacturers just won't deliver, it's more likely the analogue oscilloscopes have been superseded. Even with their inferior XY modes the world at large seems to prefer DSOs over CROs and the areas where CROs still fare better are apparently not vital to those using them in earnest. Although it's more likely the inferior areas aren't well developed because few people require them. The beauty of CROs being delegated to more casual use in general is that people get to enjoy them for reasons other than sheer functional productivity, like the visceral experience of pushing and pulling clunking buttons and switches.
 

Offline David Hess

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #129 on: August 06, 2019, 06:47:01 am »
I would be happy if someone made a DSO with the advantages of an analog oscilloscope and a good user interface but nobody even bothers even though I know it is possible.  I am slowly working on my own design but more for fun than any practical use.
 

Offline tggzzz

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #130 on: August 06, 2019, 06:59:48 am »

Why do you ask is more important ?
 
I use one. But is it time to upgrade to DSO now?

You currently have no ability to capture a single shot or non-repetitive waveform and analyse it. That an enormous gap in electronics troubleshooting.

That's the killer use case for a storage scope.

But I've found it far less useful that many people claim. Why? Basically I can usually make my tests repetitive - and that's necessary during development.

The one case in the past few years when I really needed a storage scope was to look at PSU turn-on behaviour. Ironically that was in an old Tek 485 with a dodgy PSU; I could only do one test every 12 hours.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline Mr. Scram

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #131 on: August 06, 2019, 07:03:58 am »
That's the killer use case for a storage scope.

But I've found it far less useful that many people claim. Why? Basically I can usually make my tests repetitive - and that's necessary during development.

The one case in the past few years when I really needed a storage scope was to look at PSU turn-on behaviour. Ironically that was in an old Tek 485 with a dodgy PSU; I could only do one test every 12 hours.
How would you make something like button bounce reliably repetitive?
 

Offline tggzzz

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #132 on: August 06, 2019, 07:05:16 am »
When talking about menus and such, the interface of older technology tends to be much more accessible - after all, the options are entirely enclosed in the front panel and not hidden under tabs, drawers, doors, etc. (the physical equivalent of soft menus).

The problem is how to aggregate the plethora of new options in such small panel. Sure, a Tek 555 sized gear could probably have enough real state to accommodate all the options in a DS1054Z.

That's a significant issue, of course.

It is not an issue at all; modern DSO interfaces (and other test instruments) are just poorly designed.

That's the significant issue :(
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Online Electro Detective

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #133 on: August 06, 2019, 09:21:02 am »
I would be happy if someone made a DSO with the advantages of an analog oscilloscope and a good user interface but nobody even bothers even though I know it is possible.

I am slowly working on my own design but more for fun than any practical use.

One of the manufacturers may work that out one day, so that the user can plug into the standalone DSO via USB etc, with customizable software installed on their computer,
so that they can access the DSO and rig it the way they want, with preset analogue/digital/retro flavors to choose from as well.

Add a touch screen monitor to the mix to act as the control panel and you have what dumbass noise vending  DeeJays already have now, and have had for years,
USB interface hardware and programs like VirtualDJ and the other funny named ones that are too complicated because they can be, which appeal to music appreciation challenged so called DeeJays
that don't know how to use them, but pretend they do..
and never will, going by their bad taste in music, slackness in 'reading the crowd', and unaware of their pending deafness, and their unfortunate eckied/iced music appreciation challenged followers  ::)

 

Online bd139

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #134 on: August 06, 2019, 09:24:19 am »
I don't find DSO interfaces terrible. At least HP 54600 series, Tek TD200 series and DS1000Z series.

Granted there are some annoyances but nothing particularly end game. I am lazy enough just to whack auto most of the time then tidy up what remains :)
 

Offline 001

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #135 on: August 06, 2019, 10:23:58 am »
AWESOME  :-+
 

Offline Alex Nikitin

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #136 on: August 06, 2019, 11:17:14 am »
Horses for courses I suppose. I have three analogue scopes and one DSO in my home lab. The DCO gets used maybe 1% of the time, when I need the singe event/slow event/storage capabilities. For the rest of my work there (audio, tape recorders, metrology, some RF stuff) analogue scopes work better for me. At work I have the opposite, on my bench there are three DCOs and only one simple analogue scope (which I would use for a quick troubleshooting and fault finding - so not very often).

Here is my summary:

Analogue scopes

Advantages

1) Important. Telling the truth most of the time. What you see is what you get. If you can see something, it is usually there.

2) Can see things which DCOs have great difficuly in seeing. Like AM RF or a mild 25Mhz oscillation in a power amplifier on a particular part of 1kHz sinewave... .

3) Quick. Both in startup and reaction when you touch a point with the probe.

4) Usually considerably cheaper.
 
Disadvantages

1) Can not do what DSOs do easily (single events, precise timing, easy screenshots, quick measurements, FFT, comms etc)


DSOs

Advantages:

what their analogue counterparts can not do - see above.

Disadvantages

1) DCOs are untruthful by their nature. Unless you know beforehand what you are looking for, what is on the screen may have nothing to do with the reality. Which creates a particular problem when you are troubleshooting... . You have to check and cross-check what you see to be sure.

2) Almost useless in some situations (see above, especially if you don't know what to expect, say with RF oscillations in an analogue circuit with a slow changing signal).

3) Slow. Slow in start up, slow in operation, slow in the reaction on the probe. You get used to it, however if I need to fire a scope and do a quick fault-finding in an analogue circuit, an analogue scope saves a lot of time, in most cases I would see the problem before a DCO would finish the boot-up sequence... .

Cheers

Alex


 
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Online edigi

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #137 on: August 06, 2019, 01:04:22 pm »
For me DSO only.
Apart from price (and DSOs have very steep pricing when it comes to e.g. bandwidth) and a few quirks (like slow boot/crappy shared controls etc.) from functionality perspective DSO always wins hands down.

2) Can see things which DCOs have great difficuly in seeing. Like AM RF or a mild 25Mhz oscillation in a power amplifier on a particular part of 1kHz sinewave... .

I don't see the difficulty. Even entry level scopes have nowadays 10M+ sample memory so if you make a 10ms capture (10 periods of the 1kHz signal) with 1GSa/s it fits into memory and can check both the 1kHz and 25MHz signal.
More advanced DSOs can have even more memory.
Note: In my view (and limited experience) it helps a lot also if you know what to expect (to trigger properly) or in other words you know what to look for.

Many recent features like very big FFT can come handy sometimes even if you have SA (I happen to have that as well), as you may not have high impedance input or the various probes to the SA that you may have with the scope.
Others things like protocol decoding I don't see such a big deal, actually for simple stuff I'm just too lazy to setup the DSO properly and just decide based on what I see if it's OK or not, that could be done also using analogue scope (would not work for more complex messages).

Sure if you work with low frequency analogue stuff mostly DSO brings little if any benefit (if we forget about lab space, noise and heat generated).
Also DSO can mean learning or re-learning stuff, so it may move you out of your comfort zone that not everybody is so keen of.
« Last Edit: August 06, 2019, 01:06:35 pm by edigi »
 

Offline David Hess

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #138 on: August 06, 2019, 10:24:05 pm »
You currently have no ability to capture a single shot or non-repetitive waveform and analyse it. That an enormous gap in electronics troubleshooting.

That's the killer use case for a storage scope.

I agree; easy single shot acquisitions are a killer feature of a digital storage oscilloscope if you need it.  Analog storage can do it also of course but it is not nearly as easy to use and I would never recommend it.

The oscilloscope which sits on my bench is a Tektronix 2232 which is both analog and digital storage.  While I would like a modern DSO to replace it, none have qualified without costing a house.  Maybe I need to look for one that I can live in.

2) Can see things which DCOs have great difficuly in seeing. Like AM RF or a mild 25Mhz oscillation in a power amplifier on a particular part of 1kHz sinewave... .

I don't see the difficulty. Even entry level scopes have nowadays 10M+ sample memory so if you make a 10ms capture (10 periods of the 1kHz signal) with 1GSa/s it fits into memory and can check both the 1kHz and 25MHz signal.
More advanced DSOs can have even more memory.
Note: In my view (and limited experience) it helps a lot also if you know what to expect (to trigger properly) or in other words you know what to look for.

That is one place where modern DSOs have repeatedly let me down compared to an analog oscilloscope.  I have diagnosed circuits where I suspected there was a local oscillation, like in an emitter follower from offset or operating point changes, and was able to verify it with an analog oscilloscope because the trace was "fuzzy" at a specific location.  Then knowing exactly where to look, the DSOs I tried could not see it at all. (1)

Then things get worse because my analog oscilloscopes support trigger on delay so I could actually lock on to and display the oscillation but since common DSOs no longer support this triggering mode, they could not even try to do this, except of course for my trusty old Tektronix 2230/2232 which has analog triggering and trigger on delay so it could not only lock onto just the oscillation, but then in DSO mode average out any noise to display it.

(1) My 400 MHz 7854 10-bit *1 MS/s* DSO (sort of) with its puny record length could catch it.  Oddly enough so could any of my *analog* sampling oscilloscopes.  To me that suggests that any good 10 or 12 bit DSO could also so maybe they do have a use other than marketing and emptying your bank account.
 

Offline vk6zgo

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #139 on: August 06, 2019, 11:53:08 pm »
With delayed sweep you see two traces for each input: The main trace with the A timebase, and an expanded trace running at the faster B timebase. The portion displayed by the B timebase trace is intensified on the A timebase trace which gives the context. Note that the dual time base feature  exists for single as well as dual beam scopes.

For those of us that grew up with dual time base scopes, it is second nature to pull the time/div knob and rotate it clockwise to get the faster B sweep speed.

It is worth mentioning *why* delayed timebases existed.  It was for more than a magnified view.

Delayed timebases implement "slideback" measurements which are more accurate than counting divisions on the CRT.  That is why the delay control either has calibrated markings or a readout of delay time.  If you align a waveform feature on the graticule and then align a second waveform feature on the graticule, then the difference in the delay control settings is the duration between the waveform features.  This measurement has higher accuracy because it does not rely on CRT calibration or linearity.  Some later instruments supported dual *delta* delay timebases which displayed two separate delayed sweeps allowing the direct readout of the time or frequency.

DSOs never really needed delayed sweep for measurements so it eventually became rare.  They could use cursors or automatic measurements.

I could count the number of times I had to use a delayed timebase in the described manner on the fingers of one hand.
Working in Television, there was always a known source of timing reference available in the video waveform itself.
If you are finding a "glitch" that was not inherent to the original signal absolute accuracy was not all that important.

I'm not disputing the original reason for delayed sweep, more pointing out that many users  found the other advantages of this facility of primary importance.
 

Offline Alex Eisenhut

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #140 on: August 07, 2019, 12:01:28 am »
Is this what they mean by an analog storage scope?
 
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Offline 0culus

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #141 on: August 07, 2019, 04:32:47 am »
You currently have no ability to capture a single shot or non-repetitive waveform and analyse it. That an enormous gap in electronics troubleshooting.

That's the killer use case for a storage scope.

I agree; easy single shot acquisitions are a killer feature of a digital storage oscilloscope if you need it.  Analog storage can do it also of course but it is not nearly as easy to use and I would never recommend it.

snip

I would agree with this. I own one analog storage 'scope (HP 1727A) and while single shot acquisition does work, it's rather fiddly to get right. Whereas, the digital scopes I use at work make single shot really a matter of setting up the appropriate timebase and vertical settings, and pressing a button.
 

Offline David Hess

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #142 on: August 07, 2019, 05:48:53 am »
I could count the number of times I had to use a delayed timebase in the described manner on the fingers of one hand.
Working in Television, there was always a known source of timing reference available in the video waveform itself.
If you are finding a "glitch" that was not inherent to the original signal absolute accuracy was not all that important.

I'm not disputing the original reason for delayed sweep, more pointing out that many users  found the other advantages of this facility of primary importance.

Video is where "trigger on delay" is especially useful.  Trigger on delay allows the delayed sweep to track the signal so you can count the sync pulses and then start the sweep synchronized at a specific point of the video signal without any jitter.
 

Offline vk6zgo

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #143 on: August 07, 2019, 07:15:24 am »
I could count the number of times I had to use a delayed timebase in the described manner on the fingers of one hand.
Working in Television, there was always a known source of timing reference available in the video waveform itself.
If you are finding a "glitch" that was not inherent to the original signal absolute accuracy was not all that important.

I'm not disputing the original reason for delayed sweep, more pointing out that many users  found the other advantages of this facility of primary importance.

Video is where "trigger on delay" is especially useful.  Trigger on delay allows the delayed sweep to track the signal so you can count the sync pulses and then start the sweep synchronized at a specific point of the video signal without any jitter.

Indeed, & that is how I used it.
I very seldom used it for formal "slideback" measurements, but being able to look at individual lines (& parts of those lines) was invaluable.
 

Offline vk6zgo

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #144 on: August 07, 2019, 07:29:15 am »
That's the killer use case for a storage scope.

But I've found it far less useful that many people claim. Why? Basically I can usually make my tests repetitive - and that's necessary during development.

The one case in the past few years when I really needed a storage scope was to look at PSU turn-on behaviour. Ironically that was in an old Tek 485 with a dodgy PSU; I could only do one test every 12 hours.
How would you make something like button bounce reliably repetitive?

You could make an electromechanical device to push the button at accurately determined intervals. ;D

It is hard, but you can look at things like button bounce with a non-storage CRO free running at a very low speed & set to high intensity.
Just press the button, & you will see the bounces----- stir & repeat.

Not a very good method, no permanent record, but if you think the problem is switch bounce, it will confirm this.
In many cases, it is a "Fix the bloody thing!" situation, & going "cap in hand" to the Boss saying "Please, Sir---I need a Storage 'scope, preferably a DSO." just won't fly!
 

Offline tggzzz

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #145 on: August 07, 2019, 08:25:37 am »
That's the killer use case for a storage scope.

But I've found it far less useful that many people claim. Why? Basically I can usually make my tests repetitive - and that's necessary during development.

The one case in the past few years when I really needed a storage scope was to look at PSU turn-on behaviour. Ironically that was in an old Tek 485 with a dodgy PSU; I could only do one test every 12 hours.
How would you make something like button bounce reliably repetitive?

Using my finger, I have done exactly that on a non-storage scope, many times.

Sure a digital scope would have made it easier, but it didn't give me any more useful information.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Online bd139

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #146 on: August 07, 2019, 09:24:38 am »
Right tools for the job. Use a universal counter for debouncing stuff  :-//
 

Online Electro Detective

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #147 on: August 07, 2019, 10:26:19 am »

A bit of drilling and soldering, 2 Morse code boxes and 2 Singer sewing machine foot switches

gets the 'never miss any event again' job done here   :clap:

Facepalm aside, it can be done, especially if the DSO Stork gets h!jacked   

 

Offline Tom45

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #148 on: August 07, 2019, 04:39:18 pm »
An early example where I used delayed sweep was looking into a problem with an 854 CDC disk pack drive.

Being a removable pack, they didn't spin very fast in comparison to today's hard drives. As this was nearly 50 years ago, I don't remember the actual speed. But it was probably in the 100s of RPMs rather than 1000s. See below: it was 40 RPM.

So a transfer was two steps. First send a seek command to some address. When the disk heads had moved to the correct cylinder, and the disk rotation was close to the desired sector, an interrupt was sent. Then a read or write command was given. Because the desired sector was close to being under a head when the seek interrupt arrived, there was only a slight delay before the read or write transfer could start. With a bunch of drives (we had 24) a lot of seek commands could be underway in parallel so the effective overall seek time was very much smaller than the actual seek time of a drive.

However one drive wasn't right. At the time of the seek interrupt it wasn't close to where it needed to be.

So using a Tek 547 scope I looked at the data stream coming from the read head while triggering on an index pulse that was at the start of a revolution.

Then using delayed sweep, I could step through the addresses for an entire revolution. It turned out that the sector counter was broken. It did count all the sectors, but not in order. I think one bit of the sector address was flipped. So a seek to sector N should normally give an interrupt at sector N-d (I don't remember the value of d). Because of the bad counter, d sectors after N-d wasn't N. So there could be as much as an entire revolution of the platter before the I/O actually started.

I reported the problem to the onsite CDC guys and they found and fixed the problem in the controller. The controller was the size of a refrigerator and was all discrete components. No ICs.

Well, I got curious and did a search on the CDC 854 drive. A sales document is at:

https://archive.computerhistory.org/resources/text/CDC/CDC.Disk_852-4.ca1970.102646314.pdf

The rotation speed was 40 RPM, or 25 msec per rev. Overlapping seeks was very necessary.
 
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Offline Mr. Scram

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Re: Do You still use analog oscilloscopes in 2019?
« Reply #149 on: August 07, 2019, 04:54:49 pm »
Right tools for the job. Use a universal counter for debouncing stuff  :-//
Putting a universal counter on every button of my products made for steep prices. ;D It's not about debouncing, it's about knowing how big your bounce is so you can build a debounce mechanism with purpose whether it's hard- or software.
 


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