OT: scope recommendations?
Smitty Two
electronics, and has need for a basic scope. I told him he could borrow
my old one, since I don't use it much anymore. But, he's thinking about
getting his own, and I have no idea what's available these days. Any
suggestions about:
manufacturers to look at or avoid
distributor recommendations
used from ebay?
standalone vs. handheld scopemeter vs. PC based
would be welcome. Requirements are minimal, dual trace would be nice but
we aren't talking about stratospheric frequencies or many bells and
whistles. Personally I like the standalone with the physical knobs and
switches, but maybe some of the handhelds or the PC based units with
soft controls are decent these days.
TIA, of course.
GS
Seems like an awful question. But, I would say go Ebay with something
cheap and is
working properly.
I use to suggest Hameg analog/digital scopes, but that was before I
tried to use one !!!
greg
Rich Webb
PC-based USB-interfaced 'scopes tend not to have stellar sample rates.
There's usually a note in the fine print that the advertised sample rate
is "equivalent time sampling" which is okay for repetitive waveforms but
not so much for single event captures -- and single events are one of
the nice things you get with digital scopes.
GW Instek and Rigol each have reasonably-priced 100 MHz, 1 Gsps dual
channel models that could be a starting point for comparison
http://www.tequipment.net/InstekGDS-2102.html
http://www.tequipment.net/RigolDS1102E.html
--
Rich Webb Norfolk, VA
Charles
"Smitty Two" wrote in message
news:prestwhich-E20E4...@mx01.eternal-september.org...
If your friend can wait, the hamfests coming up often have great buys on
scopes. He should be accompanied by someone who knows what to look for and
he should deal with someone local in case there is a problem.
Jeffrey Angus
> A friend is being coerced by circumstance into learning
> a bit of electronics, and has need for a basic scope.
Ya know, just about any CRT based scope will work.
The real key is learning how to look at the trace
and "see" what it's trying to tell you.
Jeff
mike
"learning a bit of electronics"?
audio electronics?
microwave electronics?
cellphone modulation electronics?
The optimum scope is CRITICALLY dependent on what you're gonna do with it.
You get more bang for the buck with an older analog scope...
until you run out of capability for your application.
Second the hamfest idea.
But you can also visit a local ham club and ask around.
Most of us have more than one...o...5 scopes in the attic.
If you don't know what you're doing, borrowing a scope 'till you do
is an option.
Do him a favor and force your old scope on him temporarily.
Gerard Bok
<prest...@earthlink.net> wrote:
>A friend is being coerced by circumstance into learning a bit of
>electronics, and has need for a basic scope.
For basics, I would advice him to run a soundcard-as-scope
program on his PC. Freeware widely available and suitable for
basic stuff.
Let him note the limitations he observes and that will give him
his 'shopping list' when buying a real scope.
>Requirements are minimal, dual trace would be nice but
>we aren't talking about stratospheric frequencies or many bells and
>whistles.
See ? :-)
--
Kind regards,
Gerard Bok
N_Cook
news:4d286e4d...@News.Individual.NET...
I've never used a pc scope - is it easy for a novice (or absent minded
old-hand) putting the probe where he shouldn't and blowing up the whole pc ,
not just the input FETs
Gerard Bok
wrote:
>Gerard Bok <bok...@zonnet.nl> wrote in message
>news:4d286e4d...@News.Individual.NET...
>> On Fri, 07 Jan 2011 06:24:12 -0800, Smitty Two
>> <prest...@earthlink.net> wrote:
>>
>> >A friend is being coerced by circumstance into learning a bit of
>> >electronics, and has need for a basic scope.
>>
>> For basics, I would advice him to run a soundcard-as-scope
>> program on his PC. Freeware widely available and suitable for
>> basic stuff.
>> Let him note the limitations he observes and that will give him
>> his 'shopping list' when buying a real scope.
>I've never used a pc scope - is it easy for a novice (or absent minded
>old-hand) putting the probe where he shouldn't and blowing up the whole pc ,
>not just the input FETs
What's cheaper, blowing a scope's input FETs or blowing a PC's
soundcard ? And what's easier to repair / replace ?
Imho scopes are both less foolproof and less forgiving than PCs.
You may not agree, but I stand by my advice.
I can only add, that --indeed-- some folks shouldn't be allowed
to be to close to anything that has wires attached.
For those folks: learn electronics by books only, don't try hands
on ;-)
nesesu
>
> - Show quoted text -
I have had concerns about that myself, especially since most PCs that
I have seen in at least the last 10 years have the 'sound card'
imbedded into the motherboard rather than being a plug in. Since the
voltage range of the sound input is likely only +/- 12V [or less] I
would also think that some form of variable attenuator is needed
'outboard' if the intention is to measure any signals [voltages]
greater than common logic levels.
On the other hand, I have worked with 'scopes in R&D for the last 50
years and can recall only one case where a 'scope input was damaged,
and that due to gross stupidity.
Neil S.
Smitty Two
mike <spa...@gmail.com> wrote:
Yeah, I think loaning him mine is best for now, and keeping an eye on
Craigslist in the meantime. Gotta be more than a few scopes gathering
dust in garages and attics.
As far as what he's doing, one usenet dilemma is balancing too little
info against too much info. But since you asked ... My friend transfers
film for a living (mostly old 8mm home movies onto DVD) and is designing
/ building a "flash scanner" which rather than stopping the film at
every frame, runs the film continuously and relies on a very bright,
very short duration strobe to freeze and capture the image directly onto
a video camera.
The project involves several disciplines and a modest amount of systems
integration to tie it all together. I've been working with him a bit on
the mechanical design aspect and doing some machining for him. He's
trying to learn enough electronics (and I don't know enough to be of all
that much help to him on that end) to figure out how to sync the film,
the strobe, and the camera together.
mike
Not clear how the strobe improves on the flash of light you get from the
shutter in the projector???
You're trying to sync the film, the flash and the scanner.
I'd just use a standard mechanical shutter and a photocell,
to sense the already-synchronized light flash to control
the projector speed...all PLL'd to the scanner acquisition rate.
That'd allow simple phase control.
If you're not working on the digitizer, most of your problems will be
with synchronization. You're gonna want a DC coupled scope with STABLE
DC coupled triggering to work at low frame rates. That takes soundcard
acquisition off the table.
Smitty Two
mike <spa...@gmail.com> wrote:
>
> Not clear how the strobe improves on the flash of light you get from the
> shutter in the projector???
One problem with using off-the-shelf projectors, as he has been doing
for many years, is duty cycle. They aren't meant to run all day long,
especially at double speed, as he does to improve throughput. The
pull-down claw mechanism in particular takes a beating, and with beat-up
decades-old film a lot of the sprocket holes are chewed up already; the
resultant "jump" is something he wants to take out of the finished
product. Keeping the film rolling at a constant speed instead of
starting and stopping it 30 times per second has its advantages.
> You're trying to sync the film, the flash and the scanner.
> I'd just use a standard mechanical shutter and a photocell,
> to sense the already-synchronized light flash to control
> the projector speed...all PLL'd to the scanner acquisition rate.
> That'd allow simple phase control.
I'm not understanding this. If it's a strobe, why would you need the
mechanical shutter? The camera has its own shutter.
>
> If you're not working on the digitizer, most of your problems will be
> with synchronization. You're gonna want a DC coupled scope with STABLE
> DC coupled triggering to work at low frame rates. That takes soundcard
> acquisition off the table.
Thanks for that note.
mike
> In article <igcvde$muj$1...@news.eternal-september.org>,
> mike <spa...@gmail.com> wrote:
>
>> Not clear how the strobe improves on the flash of light you get from the
>> shutter in the projector???
>
> One problem with using off-the-shelf projectors, as he has been doing
> for many years, is duty cycle. They aren't meant to run all day long,
> especially at double speed, as he does to improve throughput. The
> pull-down claw mechanism in particular takes a beating, and with beat-up
> decades-old film a lot of the sprocket holes are chewed up already; the
> resultant "jump" is something he wants to take out of the finished
> product. Keeping the film rolling at a constant speed instead of
> starting and stopping it 30 times per second has its advantages.
>
>> You're trying to sync the film, the flash and the scanner.
>> I'd just use a standard mechanical shutter and a photocell,
>> to sense the already-synchronized light flash to control
>> the projector speed...all PLL'd to the scanner acquisition rate.
>> That'd allow simple phase control.
>
> I'm not understanding this. If it's a strobe, why would you need the
> mechanical shutter? The camera has its own shutter.
I know zip about this, beyond the 15 minutes I spent googling and
two hours thinking about it...but I never let incompetence stop me
from pontificating...
I just picked some round numbers to make the math easy, but it scales
for whatever real numbers you're using.
At 50 FPS, you have 20ms per frame. If you use 1000 pixels acquisition
and you want to keep the image smear to one pixel, you have 20us flash
duration
at 1000X intensity. Assuming your digitizer can handle that level of
peak intensity and behave linearly, all you have left to worry about
is synchronizing a mechanical system with the video detector and the
flash. If there's 10mm between frames, all you need is 10um mechanical
stability in the film transport mechanism from frame to frame.
Much easier if you can tolerate lower resolution and lots of image smear.
No need to make the electronics any more capable than the weakest link.
Also, your light source may not have been designed to run at 50Hz.
forever. About 40 years ago, a guy at Tektronix did an experiment
where he tested transistors under pulsed conditions. Turned out that
at the rates we're talking about, you get full excursion of junction
temperature and the life of devices was significantly reduced.
That was a long time ago, and there are a LOT of variables.
Dunno if it still applies to current devices.
Sounds like a fun project.
Jim Yanik
news:4d29cf9e...@News.Individual.NET:
a scope's input-Z and circuit loading is known and minimal
(1 MegR,~20-40pf),where a soundcard will have a much lower Z and more
circuit loading. Newbies will not be aware of such loading effects.
I'd go for a TEK low end LCD scope,for a new model. TDS2200?
for a beginner on a tight budget,maybe a T922/T932/T935,those can be had
very inexpensively,are simple to operate.
--
Jim Yanik
jyanik
at
localnet
dot com
Smitty Two
mike <spa...@gmail.com> wrote:
At first I thought you meant ditch the strobe, but then for some reason
decided that wasn't what you meant. I asked him about that a month or so
back, and suggested a mechanical shutter. It turns out, he says, that
the light draws about 400 amps or something ridiculous like that, in
order to be bright enough since it's only on for a few microseconds as
you say. That's a bunch of current and heat to worry about if the light
was on constantly.
He's looked into and rejected a few different light types, and don't
recall offhand what he's settled on for now, but I agree that lots of
different problems could crop up.
Not sure whether I'd classify the project as fun or not. I admire his
determination, but I worry that his optimism is misguided. The
off-the-shelf flash scanners wouldn't cost 60k if they were easy to
design, engineer, and manufacture.
Michael A. Terrell
How many scopes have you blown up? I've used them for 45 years and
never blown up the input on one.
--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.
N_Cook
news:prestwhich-B31DC...@mx02.eternal-september.org...
Am I missing something here - why real time speed of 24 fps or whatever for
8mm.
Slow it right down and software to convert to real time colour correction
/scratch "removal" etc , audio synced in off realtime or speeded up
separately .
Gerard Bok
<prest...@earthlink.net> wrote:
>In article <igcvde$muj$1...@news.eternal-september.org>,
> mike <spa...@gmail.com> wrote:
>> Not clear how the strobe improves on the flash of light you get from the
>> shutter in the projector???
>
>One problem with using off-the-shelf projectors, as he has been doing
>for many years, is duty cycle.
From what I read here, I would suggest your friend to put the
frame scan setup aside for a while and investigate the use of a
linescanner.
That will allow him to ditch the jumpy filmtransport altogether
and scan the film right upto the maximum (continuous) speed his
electronics can handle and convert.
(That's the very same way some old microfilmscanners operated :-)
Gerard Bok
I've never blown a scope :-)
But N_Cook was worried someone would :-)
Jim Yanik
I've replaced a lot of blown input FET pairs on TEK scopes.
also several melted input BNCs.
and replaced countless power cords that had their ground pin cut off.
Michael A. Terrell
Him, I can understand.
I've repaired a lot of scopes, put they were mostly bad transformers
or power supplies. I saw a lot of bad resistors in the Focus/Intensity
circuit on cheap scopes too.
Smitty Two
bok...@zonnet.nl (Gerard Bok) wrote:
> On Sun, 09 Jan 2011 13:55:13 -0800, Smitty Two
> <prest...@earthlink.net> wrote:
>
> >In article <igcvde$muj$1...@news.eternal-september.org>,
> > mike <spa...@gmail.com> wrote:
>
> >> Not clear how the strobe improves on the flash of light you get from the
> >> shutter in the projector???
> >
> >One problem with using off-the-shelf projectors, as he has been doing
> >for many years, is duty cycle.
>
> From what I read here, I would suggest your friend to put the
> frame scan setup aside for a while and investigate the use of a
> linescanner.
What's a linescanner?
Smitty Two
"N_Cook" <div...@tcp.co.uk> wrote:
>
>
> Am I missing something here - why real time speed of 24 fps or whatever for
> 8mm.
> Slow it right down and software to convert to real time colour correction
> /scratch "removal" etc , audio synced in off realtime or speeded up
> separately .
I'm not understanding this. He definitely doesn't want to slow the film
down; he usually runs it at 2x. Your second sentence doesn't grok.
Smitty Two
Rich Webb <bbe...@mapson.nozirev.ten> wrote:
>
> PC-based USB-interfaced 'scopes tend not to have stellar sample rates.
> There's usually a note in the fine print that the advertised sample rate
> is "equivalent time sampling" which is okay for repetitive waveforms but
> not so much for single event captures -- and single events are one of
> the nice things you get with digital scopes.
Noted, thanks.
>
> GW Instek and Rigol each have reasonably-priced 100 MHz, 1 Gsps dual
> channel models that could be a starting point for comparison
> http://www.tequipment.net/InstekGDS-2102.html
> http://www.tequipment.net/RigolDS1102E.html
A tad spendy for his needs and budgets, but I appreciate the suggestions.
Smitty Two
Jim Yanik <jya...@abuse.gov> wrote:
> I'd go for a TEK low end LCD scope,for a new model. TDS2200?
>
> for a beginner on a tight budget,maybe a T922/T932/T935,those can be had
> very inexpensively,are simple to operate.
Thanks, I'll look into those. Seems like a good fit for him.
Jeffrey Angus
> for a beginner on a tight budget,maybe a T922/T932/T935,
> those can be had very inexpensively,are simple to operate.
Weren't those the ones made as a joint effort with Sony?
Sort of Tek's experiment with bottom feeding?
Not good enough for the lab and too expensive for the shop.
Jeff
George Herold
> In article <djeei65go3b9sa9p3rb0mku609jfef5...@4ax.com>,
I've got a 50MHz Rigol that I like. DS1052. $400.00
We bought OWON for a bit less, But I would stay away from that one.
George H.
josephkk
wrote:
>In article <4d2acac...@News.Individual.NET>,
> bok...@zonnet.nl (Gerard Bok) wrote:
>
>> On Sun, 09 Jan 2011 13:55:13 -0800, Smitty Two
>> <prest...@earthlink.net> wrote:
>>
>> >In article <igcvde$muj$1...@news.eternal-september.org>,
>> > mike <spa...@gmail.com> wrote:
>>
>> >> Not clear how the strobe improves on the flash of light you get from the
>> >> shutter in the projector???
>> >
>> >One problem with using off-the-shelf projectors, as he has been doing
>> >for many years, is duty cycle.
>>
>> From what I read here, I would suggest your friend to put the
>> frame scan setup aside for a while and investigate the use of a
>> linescanner.
>
>What's a linescanner?
>
>> That will allow him to ditch the jumpy filmtransport altogether
>> and scan the film right upto the maximum (continuous) speed his
>> electronics can handle and convert.
>> (That's the very same way some old microfilmscanners operated :-)
Basically it captures one line at a time. Step and repeat for umpty
hundred (or few thousand) lines to get a frame. The same counters that
align the framing are used here as well. Continuous lamp focused as a
line (or special and expensive "line lamp").