Analog scopes for noise measurements

In article <nTTFe.7523$_%4.4375@newssvr14.news.prodigy.com>,
Joerg <notthisjoergsch@removethispacbell.net> wrote:

[snip]

The DSOs I worked with including the expensive kind didn't seem to have
anywhere near nine effective bits. Oversampling doesn't help if you are
after a tiny runt pulse that happens once in a blue moon or randomly.
For EMI work I hardly ever use a DSO.

Regards, Joerg

http://www.analogconsultants.com
Click to expand...
Some _emit_ a lot of noise via the _inputs_. Try connecting the input
of a Tek TDS210 with an analog scope, and look at the analog scope's display.
Amazing :(

-frank
--
 
Hello Frank,

Some _emit_ a lot of noise via the _inputs_. Try connecting the input
of a Tek TDS210 with an analog scope, and look at the analog scope's display.
Amazing :(
Click to expand...
Even more amazing: I almost pulled my hair out on an EMI case although I
am pretty seasoned in the art. What on earth...? Then I had a hunch
since I was using the client's spectrum analyzer and that one just
looked too glitzy to me. A newfangled thing with flat panel display and
the whole enchilada. It probably even had some function to pre-order a
Starbucks Cappucino via the web.

Took the EMCO sniffer to it and, bingo. All the stuff I saw came out of
that display. So, as weird as it may sound the drill changed to "eat
chocolate and clean foil wrapper", "cover screen with foil wrapper",
"measure and store", "uncover screen to look at results". I was thankful
that the store button wasn't a touch screen function so I didn't have to
do the "poke tooth pick through hole" routine :)

Regards, Joerg

http://www.analogconsultants.com
 
On Wed, 27 Jul 2005 13:04:15 -0700, Chris Carlen wrote:

The effective resolution of an analog scope would be the "fatness" of
the trace divided into the height of the screen.
Click to expand...
Most, if not all analog 'scopes have a dynamic range of more that one
screen height, usually several. Trace width is usually quoted as 0.5mm

High end, specialized Y amplifiers, such as the Tek 7A13 plugin, can have
an effective screen height of 10,000 divisions at 1mV per division.

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)
 
Hello Fred,

High end, specialized Y amplifiers, such as the Tek 7A13 plugin, can have
an effective screen height of 10,000 divisions at 1mV per division.
Click to expand...
Even not so high end Y amps do. My first scope was a Hameg 207 from the
early 70's and I still have it. 8MHz BW, no trigger (!) but a
"synchronizer". It's Y amp was very saturation proof. You could crank it
up and almost see the electrons dance. The only downside it the teeny
tiny CRT in it but hey, it still works like new.

Regards, Joerg

http://www.analogconsultants.com
 
Fred Abse wrote:
On Wed, 27 Jul 2005 13:04:15 -0700, Chris Carlen wrote:

The effective resolution of an analog scope would be the "fatness" of
the trace divided into the height of the screen.

Most, if not all analog 'scopes have a dynamic range of more that one
screen height, usually several. Trace width is usually quoted as 0.5mm

High end, specialized Y amplifiers, such as the Tek 7A13 plugin, can have
an effective screen height of 10,000 divisions at 1mV per division.
Click to expand...

Interesting.


Thanks for the input!



--
_______________________________________________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarleRemoveThis@BOGUSsandia.gov
NOTE, delete texts: "RemoveThis" and "BOGUS" from email address to reply.
 
On Thu, 28 Jul 2005 23:04:15 +0000, Joerg wrote:

Hello Fred,

High end, specialized Y amplifiers, such as the Tek 7A13 plugin, can have
an effective screen height of 10,000 divisions at 1mV per division.

Even not so high end Y amps do. My first scope was a Hameg 207 from the
early 70's and I still have it. 8MHz BW, no trigger (!) but a
"synchronizer". It's Y amp was very saturation proof. You could crank it
up and almost see the electrons dance. The only downside it the teeny
tiny CRT in it but hey, it still works like new.
Click to expand...
It used to be called "windowing". Manufacturers made a sales point of it.

The first digital 'scope I saw demonstrated, I asked the shiny sales guy
how far I could window the display. He didn't know what I was talking
about. He didn't seem to understand quantization noise, either, just kept
going on and on about memory depth and features I didn't want.

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)
 
On Fri, 29 Jul 2005 18:06:14 +0100, Fred Abse wrote:

On Thu, 28 Jul 2005 23:04:15 +0000, Joerg wrote:

Hello Fred,

High end, specialized Y amplifiers, such as the Tek 7A13 plugin, can have
an effective screen height of 10,000 divisions at 1mV per division.

Even not so high end Y amps do. My first scope was a Hameg 207 from the
early 70's and I still have it. 8MHz BW, no trigger (!) but a
"synchronizer". It's Y amp was very saturation proof. You could crank it
up and almost see the electrons dance. The only downside it the teeny
tiny CRT in it but hey, it still works like new.

It used to be called "windowing". Manufacturers made a sales point of it.

The first digital 'scope I saw demonstrated, I asked the shiny sales guy
how far I could window the display. He didn't know what I was talking
about. He didn't seem to understand quantization noise, either, just kept
going on and on about memory depth and features I didn't want.
Click to expand...
Did you ask him if it had ventricles?

Thanks!
Rich
 
On Fri, 29 Jul 2005 19:11:32 +0000, Rich Grise wrote:

Did you ask him if it had ventricles?
Click to expand...
No, but my final comments had quite a lot to do with testicles :)

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)
 
In article <pan.2005.07.29.19.56.34.306927@cerebrumconfus.it>, Fred
Abse <excretatauris@cerebrumconfus.it> wrote:

On Fri, 29 Jul 2005 19:11:32 +0000, Rich Grise wrote:

Did you ask him if it had ventricles?

No, but my final comments had quite a lot to do with testicles :)
Click to expand...
In digital scopes, a relatively new specification that says a lot
about the error sources in each vendor's scope is "jitter noise floor".

Comparisons of high end (high BW - 8 GHz or >) scopes today have some
with fractions of pico-second values. They all make measurements
automatically with statistics. So X and or Y scale variances can be
quantified and bounded with high degrees of confidence.

JS
 
On Sun, 31 Jul 2005 10:36:12 -0400, JS <wd1v@comcast.net> wrote:

In article <pan.2005.07.29.19.56.34.306927@cerebrumconfus.it>, Fred
Abse <excretatauris@cerebrumconfus.it> wrote:

On Fri, 29 Jul 2005 19:11:32 +0000, Rich Grise wrote:

Did you ask him if it had ventricles?

No, but my final comments had quite a lot to do with testicles :)

In digital scopes, a relatively new specification that says a lot
about the error sources in each vendor's scope is "jitter noise floor".

Comparisons of high end (high BW - 8 GHz or >) scopes today have some
with fractions of pico-second values. They all make measurements
automatically with statistics. So X and or Y scale variances can be
quantified and bounded with high degrees of confidence.

JS
Click to expand...
Some/most digital scopes don't try to synchronize the ADC sampling
clock to the trigger, so there's always 1 sample peak-peak time jitter
inherent to the architecture. Fancier digital scopes measure the time
between the trigger and the sample clock and compensate.

Equivalent-time samplers have had picosecond jitter almost from the
very first. The HP185 had 4 GHz bandwidth and tens of ps of jitter ca.
1962, using tubes. The newer ones measure RMS jitter in fs.

You can get a working 1990-vintage Tek 11801 on ebay, with a sampling
head, for around $2k, for 12-20 GHz bw and jitter of a few ps RMS. I
sometimes buy broken ones for a couple hundred bucks if the seller
reports the right diagnostic error, one we know how to fix. Somebody
could make a nice living buying the duds for, say, $200 and fixing
them and selling for, say, $2k.


John
 
"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:n24qe159r0hs9c1seqsp9v5474q2tbftcv@4ax.com...
<snip>
You can get a working 1990-vintage Tek 11801 on ebay, with a sampling
head, for around $2k, for 12-20 GHz bw and jitter of a few ps RMS. I
sometimes buy broken ones for a couple hundred bucks if the seller
reports the right diagnostic error, one we know how to fix. Somebody
could make a nice living buying the duds for, say, $200 and fixing
them and selling for, say, $2k.


John
Click to expand...
What's an example of the easier diagnostic codes to fix?

Robert
 
On Mon, 01 Aug 2005 04:06:10 GMT, "Robert" <Robert@yahoo.com> wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:n24qe159r0hs9c1seqsp9v5474q2tbftcv@4ax.com...
snip
You can get a working 1990-vintage Tek 11801 on ebay, with a sampling
head, for around $2k, for 12-20 GHz bw and jitter of a few ps RMS. I
sometimes buy broken ones for a couple hundred bucks if the seller
reports the right diagnostic error, one we know how to fix. Somebody
could make a nice living buying the duds for, say, $200 and fixing
them and selling for, say, $2k.


John

What's an example of the easier diagnostic codes to fix?

Robert
Click to expand...
Dead batteries.

John
 
On Sun, 31 Jul 2005 22:26:47 -0700, John Larkin wrote:
On Mon, 01 Aug 2005 04:06:10 GMT, "Robert" <Robert@yahoo.com> wrote:
"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message

snip
You can get a working 1990-vintage Tek 11801 on ebay, with a sampling
head, for around $2k, for 12-20 GHz bw and jitter of a few ps RMS. I
sometimes buy broken ones for a couple hundred bucks if the seller
reports the right diagnostic error, one we know how to fix. Somebody
could make a nice living buying the duds for, say, $200 and fixing
them and selling for, say, $2k.

What's an example of the easier diagnostic codes to fix?

Dead batteries.

Seriously? I've been known to rescue TVs and microwave ovens that
Click to expand...
only needed a fuse. Once I got a window air conditioner that just
had sticky bearings - a little WD-40 and I was cool all summer!
I had to get a fat extension cord, so there's something electronical
about it. ;-) Once, I saw a 27" console TV in a dumpster. I went
to take a look, and see if it was only the fuse, but the idiots
who had tossed it, tossed it - literally - and it had landed on the
neck socket. "FSssssssssssss....." )-; So I left it there.

Thanks!
Rich
 
"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:n24qe159r0hs9c1seqsp9v5474q2tbftcv@4ax.com...
Some/most digital scopes don't try to synchronize the ADC sampling
clock to the trigger, so there's always 1 sample peak-peak time jitter
inherent to the architecture. Fancier digital scopes measure the time
between the trigger and the sample clock and compensate.
Click to expand...
My understanding was that even the cheapest Tek and Agilent scopes you can buy
today do this (compensate, in software, for the difference between the sample
point and the trigger point). Anybody know for certain?
 
On Tue, 2 Aug 2005 16:15:18 -0700, "Joel Kolstad"
<JKolstad71HatesSpam@yahoo.com> wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:n24qe159r0hs9c1seqsp9v5474q2tbftcv@4ax.com...
Some/most digital scopes don't try to synchronize the ADC sampling
clock to the trigger, so there's always 1 sample peak-peak time jitter
inherent to the architecture. Fancier digital scopes measure the time
between the trigger and the sample clock and compensate.

My understanding was that even the cheapest Tek and Agilent scopes you can buy
today do this (compensate, in software, for the difference between the sample
point and the trigger point). Anybody know for certain?
Click to expand...
Neither my TDS2012 (100 MHz) nor my TDS3052 (500 MHz) does. I checked
the current 3052B datasheet, and they don't mention timebase jitter at
all, so I suspect it's still doing asynchronous sampling like my
original 3052.

My 2012 samples at 1 Gs/s and has 100 MHz bw (risetime is just about
3.5 ns) but the fastest timebase is only 5 ns/cm. That trick hides the
sample splatter pretty well.

The really high-end scopes, the $15K and up things, usually fix this
and spec jitter.

John
 
Hi John,

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:r410f1pg4c86o16difnnucqo5fr6das89p@4ax.com...
Neither my TDS2012 (100 MHz) nor my TDS3052 (500 MHz) does.
Click to expand...
Wow, that's a little disappointing! I stand corrected; thanks for the info.
 
Hello John,

My understanding was that even the cheapest Tek and Agilent scopes you can buy
today do this (compensate, in software, for the difference between the sample
point and the trigger point). Anybody know for certain?

Neither my TDS2012 (100 MHz) nor my TDS3052 (500 MHz) does. I checked
the current 3052B datasheet, and they don't mention timebase jitter at
all, so I suspect it's still doing asynchronous sampling like my
original 3052.

My 2012 samples at 1 Gs/s and has 100 MHz bw (risetime is just about
3.5 ns) but the fastest timebase is only 5 ns/cm. That trick hides the
sample splatter pretty well.
Click to expand...
I wonder why. I mean, couldn't they have used a smart oscillator design
and then yank the oscillator into phase when trigger cometh? It'll mess
up the first sample but the others would be in sync. We have done stuff
like that in ultrasound more than 10 years ago.

Regards, Joerg

http://www.analogconsultants.com
 
On Wed, 03 Aug 2005 01:03:11 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello John,

My understanding was that even the cheapest Tek and Agilent scopes you can buy
today do this (compensate, in software, for the difference between the sample
point and the trigger point). Anybody know for certain?

Neither my TDS2012 (100 MHz) nor my TDS3052 (500 MHz) does. I checked
the current 3052B datasheet, and they don't mention timebase jitter at
all, so I suspect it's still doing asynchronous sampling like my
original 3052.

My 2012 samples at 1 Gs/s and has 100 MHz bw (risetime is just about
3.5 ns) but the fastest timebase is only 5 ns/cm. That trick hides the
sample splatter pretty well.

I wonder why. I mean, couldn't they have used a smart oscillator design
and then yank the oscillator into phase when trigger cometh? It'll mess
up the first sample but the others would be in sync. We have done stuff
like that in ultrasound more than 10 years ago.

Regards, Joerg

http://www.analogconsultants.com
Click to expand...

DSOs sample continuously so they can display pre-trigger samples, so
it's too late to change the true sample times once the trigger
arrives. All you really need to do is quantify the delta-t between the
trigger and the next (or in fact any known) sample, and fudge the
display accordingly. That's not real hard to do.

John
 
In article <jJUHe.799$C11.453@newssvr21.news.prodigy.com>,
Joerg <notthisjoergsch@removethispacbell.net> wrote:
Hello John,
[...]
My 2012 samples at 1 Gs/s and has 100 MHz bw (risetime is just about
3.5 ns) but the fastest timebase is only 5 ns/cm. That trick hides the
sample splatter pretty well.

I wonder why. I mean, couldn't they have used a smart oscillator design
and then yank the oscillator into phase when trigger cometh? It'll mess
up the first sample but the others would be in sync. We have done stuff
like that in ultrasound more than 10 years ago.
Click to expand...
Or better yet, record the phase of the sample clock at the time of
triggering.

--
--
kensmith@rahul.net forging knowledge
 
In article <1s60f1pcgv72l38d5ur24lb0odadd5bbkg@4ax.com>, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Wed, 03 Aug 2005 01:03:11 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Hello John,

My understanding was that even the cheapest Tek and Agilent scopes you can
buy
today do this (compensate, in software, for the difference between the
sample
point and the trigger point). Anybody know for certain?

Neither my TDS2012 (100 MHz) nor my TDS3052 (500 MHz) does. I checked
the current 3052B datasheet, and they don't mention timebase jitter at
all, so I suspect it's still doing asynchronous sampling like my
original 3052.

My 2012 samples at 1 Gs/s and has 100 MHz bw (risetime is just about
3.5 ns) but the fastest timebase is only 5 ns/cm. That trick hides the
sample splatter pretty well.

I wonder why. I mean, couldn't they have used a smart oscillator design
and then yank the oscillator into phase when trigger cometh? It'll mess
up the first sample but the others would be in sync. We have done stuff
like that in ultrasound more than 10 years ago.

Regards, Joerg

http://www.analogconsultants.com


DSOs sample continuously so they can display pre-trigger samples, so
it's too late to change the true sample times once the trigger
arrives. All you really need to do is quantify the delta-t between the
trigger and the next (or in fact any known) sample, and fudge the
display accordingly. That's not real hard to do.

John
Click to expand...
And you usually don't want the error sources of the scope in your
measurements - so modern methods collect absolute values (periods, for
instance) and simply present the statistics. Timebase error creeps
in with ADC effective bits, preamp gain and offset, temperature, and
other gremlin noise sources.

JS
 
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