Analog & Digital scope reads of Lown wave

[Joerg]

Max65 wrote:

Hi Joerg,
yesterday night I tried to send you a private reply, but this morning
I realized that your address should refer to such kind of anti-spam
service.

There is no anti-spam, just delete "notthis" and "removethis" and it'll
work. Newsgroups are copied into the web so much that it has tio be done
to avoid spam robots. Or just use
jsc _at_ ieee _dot_ org.

I wrote you the private msg to avoid this thread to grow up with non
electronics related messages.

It's ok to discuss equipment related stuff here. In other technical
groups they even discuss politics but that can get ugly. Some of the
barbeque recipes are good though.

It has hold-off? That's a surprise. We could not make that work on the
TDS220.
May be your one was an early fw machine.

I think most were late 90's.

I had suggested that to the designers of my scope in Taiwan. They seemed
quite interested in the beginning but no new firmware has been released
yet. But as the Chinese say, patience is everything.
I hope you'll be luckier than me with it
In 1998 I discovered a bug into the frequency counter of a Korean made
test-set. I contacted the developers and explained them the problem
(they had missed the carry of the least significat word in the
reciprocal computation of the period when the counter was measuring
very low frequencies). They were lovely and willing people until I
explained them the problem, and promised me a new updated cpu (they
didn't have any ISP features in their counter, and used an eprom based
microcontroller), but when it came the time to send me that updated
device, I lost any contact with them (I'll never buy an instrument
from that factory).

Yes, got to be careful. The scope works as expected, only a few language
issues but on the other hand they crammed an enourmous amount of
languages in there. Including Italian

On self-cal it doesn't show because on the Tek series it is a conducted
noise problem, conducted when the scope probes are attached. And that
would have been rather easy to fix or completely avoid in the first
place.
My own never shown this issue, may they fixed later yours.

That's because they also make (or at least used to make) defense gear.
Mil stuff must pass much stricter emissions than lab or consumer gear,
or even medical. So these guys know how to do things right. And it's easy:
I very well know how R&S works, a good friend of mine worked for a
long time at their service department here in Italy.

Do the backlight strictly differential and common-mode choke the heck
out of that. Ferrite is still cheap (probably because it's not
oil-based...). If radiated noise is an issue lay a fine see-through mesh
over the screen. Ok, it may cost a 20% drop in translucency but on the
other hand gives the unit that robust "military" look. Or just use a
better display.
You are right, but may be they considered easier to suggest the user
to keep the DUT away from the scope screen, so they supplied you the
scope with two 5 feets long cabled probes!!! ;-)

Problem is, the long scope probes did not fix it. No, to me that is a
hardcore design flaw. Not supposed to happen at a company of this
reputation.

Stuff like this happens to all of us, when we quietly mumble "I hope
nobody saw that". Especially with consultants who sometimes are believed
to have guru status. And we are not gurus.
Nothing is more correct than you say. Almost all my skillfulness is
the result of experience on the field, which has been made of mistakes
and their fixup!

And have a nice glass of Chianti Classico for me ;-)
To be honest, I prefer a good glass of Lambrusco which is sweeter than
Chianti, but you should now that I'm not a wine expert (to be more
honest I know almost nothing about wines)
I'm from the North West of Italy, here we have the Barbera, but I
don't like it so much. I prefer white wines to the reds, so many
friends of mine tell me to continue to drink coke, that's better for
me!

I love a good Barbera. But first there has to be a good cup of espresso,
every evening. I believe you guys call it cafe.

My wife made Tiramisu yesterday. Can't wait.
Enjoy it, but take care of you weight! ;-)

Yes, I really do have to watch that. But what can you do if the smell
wafts over from the kitchen?

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Max65]

Hi Joerg,
yesterday night I tried to send you a private reply, but this morning
I realized that your address should refer to such kind of anti-spam
service.
I wrote you the private msg to avoid this thread to grow up with non
electronics related messages.

It has hold-off? That's a surprise. We could not make that work on the
TDS220.
May be your one was an early fw machine.

I had suggested that to the designers of my scope in Taiwan. They seemed
quite interested in the beginning but no new firmware has been released
yet. But as the Chinese say, patience is everything.
I hope you'll be luckier than me with it

In 1998 I discovered a bug into the frequency counter of a Korean made
test-set. I contacted the developers and explained them the problem
(they had missed the carry of the least significat word in the
reciprocal computation of the period when the counter was measuring
very low frequencies). They were lovely and willing people until I
explained them the problem, and promised me a new updated cpu (they
didn't have any ISP features in their counter, and used an eprom based
microcontroller), but when it came the time to send me that updated
device, I lost any contact with them (I'll never buy an instrument
from that factory).

On self-cal it doesn't show because on the Tek series it is a conducted
noise problem, conducted when the scope probes are attached. And that
would have been rather easy to fix or completely avoid in the first
place.
My own never shown this issue, may they fixed later yours.

That's because they also make (or at least used to make) defense gear.
Mil stuff must pass much stricter emissions than lab or consumer gear,
or even medical. So these guys know how to do things right. And it's easy:
I very well know how R&S works, a good friend of mine worked for a

long time at their service department here in Italy.

Do the backlight strictly differential and common-mode choke the heck
out of that. Ferrite is still cheap (probably because it's not
oil-based...). If radiated noise is an issue lay a fine see-through mesh
over the screen. Ok, it may cost a 20% drop in translucency but on the
other hand gives the unit that robust "military" look. Or just use a
better display.
You are right, but may be they considered easier to suggest the user

to keep the DUT away from the scope screen, so they supplied you the
scope with two 5 feets long cabled probes!!! ;-)

Stuff like this happens to all of us, when we quietly mumble "I hope
nobody saw that". Especially with consultants who sometimes are believed
to have guru status. And we are not gurus.
Nothing is more correct than you say. Almost all my skillfulness is

the result of experience on the field, which has been made of mistakes
and their fixup!

And have a nice glass of Chianti Classico for me ;-)
To be honest, I prefer a good glass of Lambrusco which is sweeter than

Chianti, but you should now that I'm not a wine expert (to be more
honest I know almost nothing about wines)
I'm from the North West of Italy, here we have the Barbera, but I
don't like it so much. I prefer white wines to the reds, so many
friends of mine tell me to continue to drink coke, that's better for
me!

My wife made Tiramisu yesterday. Can't wait.
Enjoy it, but take care of you weight! ;-)

Have a great day,

Massimo

 

[Joerg]

Max65 wrote:

Hi Joerg,
Bella Italia. Fond memories from several vacations there. Those are the
vacations where you don't really want to leave anymore at the end.
I had been in California (you are there I guess), and I can tell the
same about
your land and people (may be the old told story that "the grass on the
other side
is always greener"?)

In summer the grass turns all brown out here ;-)

It's similar on the Instek GDS2204 here in the lab, you can move outside
the window but pretty much all those scopes do not have essential
support functions such as hold-off. IOW the trigger blows apart when you
have multiple bursts.
I check the TDS210, and it has too, the hold-off can range from 500ns
to several seconds.

It has hold-off? That's a surprise. We could not make that work on the
TDS220.

The real issue is the complex method used to set it, since you need to
go into the Horizontal
menu select its soft key on the border of the screen and use the
trigger level knob to adjust
(if you selected a quick horizontal scan, you may waste a lot of time
to reach slow hold-off times).

Yes, that's the weird way almost all DSOs have to be set for scans far
outside the main window. It would have been nice to include a real
delayed trigger. Except for some modest R&D time it would cost next to
nothing.

I had suggested that to the designers of my scope in Taiwan. They seemed
quite interested in the beginning but no new firmware has been released
yet. But as the Chinese say, patience is everything.

But my main gripe with the TDS220 is the fact that it showed noise that
really wasn't there. Cost me and my client almost half an hour until I
discovered that it came out of the scope itself.
That could be the issue they fixed later in '98(circa). I did the self
cal this morning and it shows
just a noisy trace of 2mV (when set to peak detect mode which is the
worst case).

On self-cal it doesn't show because on the Tek series it is a conducted
noise problem, conducted when the scope probes are attached. And that
would have been rather easy to fix or completely avoid in the first
place. My impression is that the design review process up there wasn't
as thorough as it used to be. Or maybe because the old folks aren't
there anymore.

The 40kHz issue It was due to the LCD discharge lamps used into the
LCD display of the DSO.
But it seems to be a common issue for LCD instrumentation with cold
cathode backlight.
The day before yesterday, I did a check on my instrumentations and I
found that almost all of them have the
same problem. The only one which haven't the problem despite it uses
the cold cathode backlight, is the Rohde & Schwarz SME03 generator. I
don't really know how they solved the problem, may be they put the
lights far from the border and EM shielded them.

That's because they also make (or at least used to make) defense gear.
Mil stuff must pass much stricter emissions than lab or consumer gear,
or even medical. So these guys know how to do things right. And it's easy:

Do the backlight strictly differential and common-mode choke the heck
out of that. Ferrite is still cheap (probably because it's not
oil-based...). If radiated noise is an issue lay a fine see-through mesh
over the screen. Ok, it may cost a 20% drop in translucency but on the
other hand gives the unit that robust "military" look. Or just use a
better display. The Instek scope here has a TFT and although I turned
its brightness way down you can still see it at the far end of the
hallway. I find I get much less tired in front of that scope compared to
some of the TDS.

Anyways, the CRTs emit EM fields too, but on other frequencies.
When I had that problem, my inexperience was real culprit. That time,
I had some unshielded inductor into the front-end of a circuit used to
detect a very small laser pulsed train of 1.5ms in duration (just 750
microJoules), over a 300x300mm solar panel. I placed the circuit on
the same bench where the DSO was... and I wasted a lot of my time
dealing with it (I feel stupid now).

Stuff like this happens to all of us, when we quietly mumble "I hope
nobody saw that". Especially with consultants who sometimes are believed
to have guru status. And we are not gurus.

Have a great day, and take a intense look to the sunny California
landscape to me (lovely place).

And have a nice glass of Chianti Classico for me ;-)

My wife made Tiramisu yesterday. Can't wait. Maybe I can talk her into
making Zuppa Inglese after that. I miss the Italian restaurant we had in
our little town back in Germany.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Max65]

Hi Joerg,

Bella Italia. Fond memories from several vacations there. Those are the
vacations where you don't really want to leave anymore at the end.
I had been in California (you are there I guess), and I can tell the

same about
your land and people (may be the old told story that "the grass on the
other side
is always greener"?)

It's similar on the Instek GDS2204 here in the lab, you can move outside
the window but pretty much all those scopes do not have essential
support functions such as hold-off. IOW the trigger blows apart when you
have multiple bursts.
I check the TDS210, and it has too, the hold-off can range from 500ns

to several seconds.
The real issue is the complex method used to set it, since you need to
go into the Horizontal
menu select its soft key on the border of the screen and use the
trigger level knob to adjust
(if you selected a quick horizontal scan, you may waste a lot of time
to reach slow hold-off times).

But my main gripe with the TDS220 is the fact that it showed noise that
really wasn't there. Cost me and my client almost half an hour until I
discovered that it came out of the scope itself.
That could be the issue they fixed later in '98(circa). I did the self

cal this morning and it shows
just a noisy trace of 2mV (when set to peak detect mode which is the
worst case).
The 40kHz issue It was due to the LCD discharge lamps used into the
LCD display of the DSO.
But it seems to be a common issue for LCD instrumentation with cold
cathode backlight.
The day before yesterday, I did a check on my instrumentations and I
found that almost all of them have the
same problem. The only one which haven't the problem despite it uses
the cold cathode backlight, is the Rohde & Schwarz SME03 generator. I
don't really know how they solved the problem, may be they put the
lights far from the border and EM shielded them.
Anyways, the CRTs emit EM fields too, but on other frequencies.
When I had that problem, my inexperience was real culprit. That time,
I had some unshielded inductor into the front-end of a circuit used to
detect a very small laser pulsed train of 1.5ms in duration (just 750
microJoules), over a 300x300mm solar panel. I placed the circuit on
the same bench where the DSO was... and I wasted a lot of my time
dealing with it (I feel stupid now).

Have a great day, and take a intense look to the sunny California
landscape to me (lovely place).
Massimo

 

[Joerg]

Max65 wrote:

Well, he did not give us enough detail about the unwanted noise. It
usually helps to identify what that noise is and a scope with better
resolution can help. One good method would be for Ed to post a screen
shot.
I share your opinion, he should better explain us the problem, but it
could be he well knows that the problem wasn't real but just

Some of the lower end TDS don't have a data interface but a camera
shot would do as well.
It had but as optional device, as for the advanced triggers feature,
while the older portable THS7xx had instead as default(?!?!)

Their older "Scope Stations" had the feature, AFAIR.

Depends on how fast his glitches are.
I don't believe he have really seen any, and I believe that the heart
of an human doesn't matter of any nano seconds glitches (do you?)

I think he is looking at a defibrillator discharge curve. Minor glitches
wouldn't matter but large spikes in there can become a serious problem.

I believe he just seen

As for delayed trigger many, for example the TDS220 we've used, didn't
do that.
I'm not sure what do you mean (excuse me, but I'm italian and english
is not my native language),

Bella Italia. Fond memories from several vacations there. Those are the
vacations where you don't really want to leave anymore at the end.

Tell me if I understood: your TDS220 doesn't let you move the
horizontal position trigger out of the acquisition window?
May be I confused it with my own TDS2002, it has the "window" and the
"window zone" functions too that are similar to the delayed time-
base.
Anyways, tomorrow I'll be at office, there I still have one TDS210 and
I try with it and tell you about.

It's similar on the Instek GDS2204 here in the lab, you can move outside
the window but pretty much all those scopes do not have essential
support functions such as hold-off. IOW the trigger blows apart when you
have multiple bursts.

But my main gripe with the TDS220 is the fact that it showed noise that
really wasn't there. Cost me and my client almost half an hour until I
discovered that it came out of the scope itself. That just isn't
supposed to happen. That same week they bid on a Tek 2265 on Ebay and
got it.

Nothing futile with realizing the limits of his tools and maybe borrow a
better one for a few hours. I've had that at clients where, for example,
we suddenly realized that a particular noise had the pattern of a cell
phone burst. With the scopes they had it could not be resolved.
I don't wanna to confuse him. I explain: if he read all what we wrote
above, he could believe we don't really have care of his problem, but
just talk about DSO (that's what we did ideed).

Well, that's what newsgroups do. It's a discussion just like in a pub.
And a lot of great product ideas and problem solutions happen in pubs ;-)

Have a great day.

Massimo

--
Ciao, Joerg

http://www.analogconsultants.com/

 

[Max65]

Well, he did not give us enough detail about the unwanted noise. It
usually helps to identify what that noise is and a scope with better
resolution can help. One good method would be for Ed to post a screen
shot.
I share your opinion, he should better explain us the problem, but it

could be he well knows that the problem wasn't real but just

Some of the lower end TDS don't have a data interface but a camera
shot would do as well.
It had but as optional device, as for the advanced triggers feature,

while the older portable THS7xx had instead as default(?!?!)

Depends on how fast his glitches are.
I don't believe he have really seen any, and I believe that the heart

of an human doesn't matter of any nano seconds glitches (do you?)
I believe he just seen

As for delayed trigger many, for example the TDS220 we've used, didn't
do that.
I'm not sure what do you mean (excuse me, but I'm italian and english

is not my native language),
Tell me if I understood: your TDS220 doesn't let you move the
horizontal position trigger out of the acquisition window?
May be I confused it with my own TDS2002, it has the "window" and the
"window zone" functions too that are similar to the delayed time-
base.
Anyways, tomorrow I'll be at office, there I still have one TDS210 and
I try with it and tell you about.

Nothing futile with realizing the limits of his tools and maybe borrow a
better one for a few hours. I've had that at clients where, for example,
we suddenly realized that a particular noise had the pattern of a cell
phone burst. With the scopes they had it could not be resolved.
I don't wanna to confuse him. I explain: if he read all what we wrote

above, he could believe we don't really have care of his problem, but
just talk about DSO (that's what we did ideed).

Have a great day.

Massimo

 

[JosephKK]

fcache@gmail.com wrote:

Hi,

I am attempting to capture the Lown wave form generated by a
defibrilator analyzer. This frequency of this wave length is
approximately 200 Hz in length. To do this I have been discharging
the defib through a defibrilator analyzer. The analyzer has an output
port that allows a BNC cable to send the resulting signal to a scope.
First, I tried using a 100 MHz Tek 2235. This displayed the lown wave
form in all of its glory but only for an instant. I decided then, to
use a digital 60 MHz 2 GB/s Tek TDS 210. This scope is able to
capture the image but it shows a ton of interference on the upward
portion of the pulse. I tried swapping out the BNC cable and the
defib analyzer to no avail. What can I do to remove or filter out the
interference?

Thanks,
Ed

I would simply take a different approach. I suggest using a studio
grade (isolated) audio digitizer feeding the PC directly. A PC can
ingest that data rate smoothly and continuously for hours at a crack.
The resulting data might well please you.

Alternatively there are reasonable low cost data acquisition cards that
include DC response and great isolation / differential measurement inputs.

 

[Joerg]

Max65 wrote:

Uhmm... I'm not sure what's the meaning of this group.

I believed it has been made to help the technicians in trouble with
their job.

Ed have a problem, and wrote:

First, I tried using a 100 MHz Tek 2235. This displayed the lown wave
form in all of its glory but only for an instant.

And then he wrote again:

I decided then, to use a digital 60 MHz 2 GB/s Tek TDS 210. This scope is able to
capture the image but it shows a ton of interference on the upward
portion of the pulse.

So, I imagined that Ed's goal is to capture the Lown waveform without
the unwanted noise on the signal that the analog scope didn't show
(for this reason it's highly probable it doesn't exist indeed).
We should help him to solve his problem, not creating him another
problem such has change his digital scope, I guess.

Well, he did not give us enough detail about the unwanted noise. It
usually helps to identify what that noise is and a scope with better
resolution can help. One good method would be for Ed to post a screen
shot. Some of the lower end TDS don't have a data interface but a camera
shot would do as well.

I don't believe Ed needs to analyze gliches or any other sporadic
distortion in the Lown waveform. I believe a TDS210 is enough to reach
his goal. No matter if there are many other better DSO on the market.
He just have to deal with that unwanted noise that he knows is not
real.

Depends on how fast his glitches are.

Joerg you wrote:
Remember that delayed trigger has been left out of many DSOs. Whatever possessed them
to remove delayed trigger I'll never understand. It only takes one
counter, and maybe a 2nd one for hold-off.
Well, I don't know how much time you spent on your TDS210, but with my
TDS2002 (but the TDS210 has the same feature too) I can set the
horizontal position to 20ms using a slow horizontal scan speed, and
then increase the horizontal scan speed to 5ns and see what happened
20ms after the trigger. I'm not sure what you could see with an analog
scope with that settings. I used for about 10 years an analog scope
with the delayed time-base, but with the introduction of DSO I thanked
God because now I can see details invisible before (my old scope had
not the CRT's phosphor with the analog memory feature).

Storage of one-time events is certainly not the domain of analog scopes
unless, as you said, you've got a storage tube. I have that here but the
problem is that they fade with age.

As for delayed trigger many, for example the TDS220 we've used, didn't
do that. I hope that some day a guy from Tek reads in groups like this
and puts a real delay-trigger back in. It's so cheap and easy with DSO.

I also had to deal with FPGAs in my career, but I used logic state
analyzers with them, I have one with 48 channels to troubleshoot
complex logic.
I repeat, there is no doubt that the TDS2xx is not the DSO's state-of-
the-art , but it's a good low priced substitute of the older analog
scopes, and the Instek is too, I'm sure.

Anyways, this is the last message I write about this futile discussion
(futile for Ed who is the owner of this thread, I mean).

Nothing futile with realizing the limits of his tools and maybe borrow a
better one for a few hours. I've had that at clients where, for example,
we suddenly realized that a particular noise had the pattern of a cell
phone burst. With the scopes they had it could not be resolved.

If Ed will ask again for an aid dealing with this issue, I'm very glad
to help him (if I could).

I wish a great day to you all.

Same to you.

--
Ciao, Joerg

http://www.analogconsultants.com/

 

[Rich Webb]

On Sat, 16 Feb 2008 13:59:51 -0800 (PST), Max65 <mporzio@tele2.it>
wrote:
[snip...snip...]

I repeat, there is no doubt that the TDS2xx is not the DSO's state-of-
the-art , but it's a good low priced substitute of the older analog
scopes, and the Instek is too, I'm sure.

It's the price of being an early adapter. The TDS2xx-series were
(AFAIK) the first "budget priced" real-time DSOs. FWIW, I got a TDS220
for home use, back in the day, and -- probably because I'm pure of
heart or something -- have not had any of the various issues discussed
in the thread, so they certainly weren't all junk.

Just a data point...

--
Rich Webb Norfolk, VA

 

[Max65]

Uhmm... I'm not sure what's the meaning of this group.

I believed it has been made to help the technicians in trouble with
their job.

Ed have a problem, and wrote:

First, I tried using a 100 MHz Tek 2235. This displayed the lown wave
form in all of its glory but only for an instant.

And then he wrote again:

I decided then, to use a digital 60 MHz 2 GB/s Tek TDS 210. This scope is able to
capture the image but it shows a ton of interference on the upward
portion of the pulse.

So, I imagined that Ed's goal is to capture the Lown waveform without
the unwanted noise on the signal that the analog scope didn't show
(for this reason it's highly probable it doesn't exist indeed).
We should help him to solve his problem, not creating him another
problem such has change his digital scope, I guess.
I don't believe Ed needs to analyze gliches or any other sporadic
distortion in the Lown waveform. I believe a TDS210 is enough to reach
his goal. No matter if there are many other better DSO on the market.
He just have to deal with that unwanted noise that he knows is not
real.

Joerg you wrote:

Remember that delayed trigger has been left out of many DSOs. Whatever possessed them
to remove delayed trigger I'll never understand. It only takes one
counter, and maybe a 2nd one for hold-off.
Well, I don't know how much time you spent on your TDS210, but with my

TDS2002 (but the TDS210 has the same feature too) I can set the
horizontal position to 20ms using a slow horizontal scan speed, and
then increase the horizontal scan speed to 5ns and see what happened
20ms after the trigger. I'm not sure what you could see with an analog
scope with that settings. I used for about 10 years an analog scope
with the delayed time-base, but with the introduction of DSO I thanked
God because now I can see details invisible before (my old scope had
not the CRT's phosphor with the analog memory feature).
I also had to deal with FPGAs in my career, but I used logic state
analyzers with them, I have one with 48 channels to troubleshoot
complex logic.
I repeat, there is no doubt that the TDS2xx is not the DSO's state-of-
the-art , but it's a good low priced substitute of the older analog
scopes, and the Instek is too, I'm sure.

Anyways, this is the last message I write about this futile discussion
(futile for Ed who is the owner of this thread, I mean).

If Ed will ask again for an aid dealing with this issue, I'm very glad
to help him (if I could).

I wish a great day to you all.

Massimo

 

[Joerg]

Max65 wrote:

Hi Joerg,
it seems you dislike TDS series at all.

No, only some of the lunch-box sized ones.

No, I used and still use some TDS210, and at home I own one TDS2002
and an older portable THS710.
They have nothing to compare to the Agilent 6000 series or the Tek
3000/5000 series. Those series are the "Rolls Royce" of the DSO kind
and have great performance, but if you need a low priced scope the
TDS2xx(xx) series can be a good choice, I guess.

Tek recalled the TDS2xx and patched the ground problem, and now the
TDS210 I use always shows the right shapes also in very noisy
industrial environments.

I'd call that an embarrassment. Why was it not caught in a design
review? If we ever did that in medical electronics the FDA would have us
over the barrel.

About the 40kHz issue, I had a bad experience few years ago working on
a project where I had very low signals to amplify, and it took a lot
of time to realize that the source was that noisy display backlight!!!

Same thing, embarrassing. Why was this not caught in in-house tests?

One other issue of the TDS2xx(xx) series is the BNC connector, they
easily crack their mounting pins (usually the pcb mounting BNC
connectors have 4 pins, while the type used by Tek into the TDS2xx
scopes has just two).

When the Instek arrived I was positively surprised by the rock solid
feel to it. Almost like after I bought my first Japanese car where the
stick-shift and everything else has this feeling of exactness and
precision. Instek could have been a little more careful with
translations though. It's nice that the scope masters umpteen languages
but some phrases sound a bit rough. For example when you want to run it
via a laptop and forget to plug in the USB cable: "DSO not connect".

About the memory depth, you are right it isn't so deep, but you should
admit that in most cases you use a DSO, it doesn't matter to enlarge
the waveform and look for its sporadic glitches.

For me that's life. I get stuff from clients, designed by others so I
don't know much about the history. "It behaves erratic sometimes, could
you find out why?" Also, with the measly 1K or 2.5K of some of the Tek
boxes I might as well forget all my pulse echo tests. Remember that
delayed trigger has been left out of many DSOs. Whatever possessed them
to remove delayed trigger I'll never understand. It only takes one
counter, and maybe a 2nd one for hold-off. Dirt cheap, or since they
usually have a large FPGA in there anyway it would be free. But no, they
took it out.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

Max65 wrote:

I would say that deep memory is absolutely essential - the main advantage is it makes setting up
triggers so much easier as you can often 'grab everything' and zoom in on the parts of interest.

This is true, it's obvious that having more memory depth gives you
great advantages analyzing sporadic glitches.
But on the other hand, here we are talking about a repetitive signal
as the Lown wave of the defibrilator, suggesting Ed to change is scope
for this pourpose is a little too much I guess, or not?

If Ed wants to get to the details of his interference he might have to.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Max65]

I would say that deep memory is absolutely essential - the main advantage is it makes setting up
triggers so much easier as you can often 'grab everything' and zoom in on the parts of interest.

This is true, it's obvious that having more memory depth gives you
great advantages analyzing sporadic glitches.
But on the other hand, here we are talking about a repetitive signal
as the Lown wave of the defibrilator, suggesting Ed to change is scope
for this pourpose is a little too much I guess, or not?

Have a great day.

Massimo

 

[Mike Harrison]

On Fri, 15 Feb 2008 05:53:47 -0800 (PST), Max65 <mporzio@tele2.it> wrote:

Hi Joerg,
it seems you dislike TDS series at all.

No, I used and still use some TDS210, and at home I own one TDS2002
and an older portable THS710.
They have nothing to compare to the Agilent 6000 series or the Tek
3000/5000 series. Those series are the "Rolls Royce" of the DSO kind
and have great performance, but if you need a low priced scope the
TDS2xx(xx) series can be a good choice, I guess.

Tek recalled the TDS2xx and patched the ground problem, and now the
TDS210 I use always shows the right shapes also in very noisy
industrial environments.

About the 40kHz issue, I had a bad experience few years ago working on
a project where I had very low signals to amplify, and it took a lot
of time to realize that the source was that noisy display backlight!!!

One other issue of the TDS2xx(xx) series is the BNC connector, they
easily crack their mounting pins (usually the pcb mounting BNC
connectors have 4 pins, while the type used by Tek into the TDS2xx
scopes has just two).

About the memory depth, you are right it isn't so deep, but you should
admit that in most cases you use a DSO, it doesn't matter to enlarge
the waveform and look for its sporadic glitches.

I would say that deep memory is absolutely essential - the main advantage is it makes setting up
triggers so much easier as you can often 'grab everything' and zoom in on the parts of interest.

 

Hi,

I am attempting to capture the Lown wave form generated by a
defibrilator analyzer. This frequency of this wave length is
approximately 200 Hz in length. To do this I have been discharging
the defib through a defibrilator analyzer. The analyzer has an output
port that allows a BNC cable to send the resulting signal to a scope.
First, I tried using a 100 MHz Tek 2235. This displayed the lown wave
form in all of its glory but only for an instant. I decided then, to
use a digital 60 MHz 2 GB/s Tek TDS 210. This scope is able to
capture the image but it shows a ton of interference on the upward
portion of the pulse. I tried swapping out the BNC cable and the
defib analyzer to no avail. What can I do to remove or filter out the
interference?

Thanks,
Ed

 

[Max65]

This is just a supposition.
I know that TDS210 had a ground issue in circa 1997 (not very sure
about the date), yours may be one of those.
Try to connect the ground terminal of the scope (one of the BNC ground
or the probe compensation outlet ground) directly to the DUT ground
using an adequately sized cable (2.5 squared mm should be ok).

Have a great day.
Massimo

 

[Joerg]

fcache@gmail.com wrote:

Hi,

I am attempting to capture the Lown wave form generated by a
defibrilator analyzer. This frequency of this wave length is
approximately 200 Hz in length. To do this I have been discharging
the defib through a defibrilator analyzer. The analyzer has an output
port that allows a BNC cable to send the resulting signal to a scope.
First, I tried using a 100 MHz Tek 2235. This displayed the lown wave
form in all of its glory but only for an instant. I decided then, to
use a digital 60 MHz 2 GB/s Tek TDS 210. This scope is able to
capture the image but it shows a ton of interference on the upward
portion of the pulse. I tried swapping out the BNC cable and the
defib analyzer to no avail. What can I do to remove or filter out the
interference?

Many of the TDS2xx series are IMHO some the worst DSO designs ever to
hit the market. I flat-out refuse to use them. The TDS2xxx are a little
better but lack any serious sample memory depth. Get a better DSO. I do
this stuff with an Instek GDS-2204 with 25K buffer depth versus the
paltry 2.5K on the Teks. The best of them all is probably the new Hameg
Analog/Digital combo which AFAIK offer a whopping 1M.

And as Massimo mentioned the TDS2xx serious often has horrible noise
performance. A TDS220 once had me fooled. The 40/80kHz noise I could not
explain ended up coming out of its own power supply or backlight
inverter. I never used that scope again and advised the client to ditch
it and get a "real" scope off Ebay. Which they did.

Tek seriously needs to think about either hiring some of their older
folks back or seeking external consultants. Else the Asians are going to
eat their lunch. I mean, this ain't rocket science. I captured my first
defib discharge pattern in the early 90's with a rather old Philips
scope and the quality was good enough for the TUEV guys to bless it.

I'd give the little Teks one credit though: They are very portable. My
Instek is longer and heavier. However, IMHO it's better.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Max65]

Hi Joerg,
it seems you dislike TDS series at all.

No, I used and still use some TDS210, and at home I own one TDS2002
and an older portable THS710.
They have nothing to compare to the Agilent 6000 series or the Tek
3000/5000 series. Those series are the "Rolls Royce" of the DSO kind
and have great performance, but if you need a low priced scope the
TDS2xx(xx) series can be a good choice, I guess.

Tek recalled the TDS2xx and patched the ground problem, and now the
TDS210 I use always shows the right shapes also in very noisy
industrial environments.

About the 40kHz issue, I had a bad experience few years ago working on
a project where I had very low signals to amplify, and it took a lot
of time to realize that the source was that noisy display backlight!!!

One other issue of the TDS2xx(xx) series is the BNC connector, they
easily crack their mounting pins (usually the pcb mounting BNC
connectors have 4 pins, while the type used by Tek into the TDS2xx
scopes has just two).

About the memory depth, you are right it isn't so deep, but you should
admit that in most cases you use a DSO, it doesn't matter to enlarge
the waveform and look for its sporadic glitches.

Have a great day.
Massimo