12 and 16-bit oscilloscopes

[Chris Carlen]

Hi:

Picotech seems to be the only supplier of these in low cost <$1500 flavors.

But they are discontinuing their 16-bit version which had 96dB dynamic
range:

http://www.picotech.com/applications/resolution.html

And there USB based 12-bit versions have 72dB rather than the 80dB of
the parallel port versions. I expect they will dump the parallel ports
eventually.

This is a shame. The 16-bit unit is killer for low frequency/audio
amplifier testing and general spectrum analysis. The FFT functions on
8-bit fast DSOs from Tek and Agilent are of limited usefulness due to
meager 70dB range (with averaging).

I have been communicating with Pico to try to encourage them to keep the
16-bit or develop another one. They haven't been very responsive.

I will email the Cleverscope and notifiy them that they might consider
filling the opening Pico is leaving.



--
Good day!

________________________________________
Christopher R. Carlen
Principal Laser&Electronics Technologist
Sandia National Laboratories CA USA
[email protected]
NOTE, delete texts: "RemoveThis" and
"BOGUS" from email address to reply.

 

[Bob]

Hi:

Picotech seems to be the only supplier of these in low cost <$1500 flavors.

But they are discontinuing their 16-bit version which had 96dB dynamic
range:

http://www.picotech.com/applications/resolution.html

And there USB based 12-bit versions have 72dB rather than the 80dB of
the parallel port versions. I expect they will dump the parallel ports
eventually.

This is a shame. The 16-bit unit is killer for low frequency/audio
amplifier testing and general spectrum analysis. The FFT functions on
8-bit fast DSOs from Tek and Agilent are of limited usefulness due to
meager 70dB range (with averaging).

I wonder if picotech ever fixed the glaring bugs in their software?

My boss bought a ADC-216 when we needed an 50KHz spectrum analyser.
I'd seen picotech equipment before and reccommended buying a spectrum
analyser off ebay instead. When the picotech unit arrived I connected
it in parallel with a conventional scope and tried it out.

I found several serious software bugs. I can't remember them all now.
It has an AC voltmeter function, the spec page claims 1% accuracy. It
worked ok up to about 10KHz and above that the reading were completly
wrong. The hardware is just a fast ADC so the PC software did the task
of adding up the area of the voltage versus time graph.

A picotech support person reproduced the problems I found and promised
to send a new version of the software. Months later after a few
reminders they finally emailed me some software, the same buggy
software I'd already been supplied with the unit.

Bob

 

[Chris Carlen]

I wonder if picotech ever fixed the glaring bugs in their software?

[edit discouraging story]


Bummer. Now I'm disinclined to buy one.

Any other experiences out there?



--
Good day!

________________________________________
Christopher R. Carlen
Principal Laser&Electronics Technologist
Sandia National Laboratories CA USA
[email protected]
NOTE, delete texts: "RemoveThis" and
"BOGUS" from email address to reply.

 

[SioL]

[edit discouraging story]


Bummer. Now I'm disinclined to buy one.

Any other experiences out there?

I've purchased and used ADC216 specifically for the dynamic range in fft mode.
For this purpose it seemed very usefull to me and I was able to troubleshoot
a few things I could never have done without it.
Although I can't and did not compare its operation against any other comparable
unit.

I admit to not having used it as a scope, analogue scope is a much better
solution for that.

SioL

 

[Tom Bruhns]

Hi:

Picotech seems to be the only supplier of these in low cost <$1500 flavors.

But they are discontinuing their 16-bit version which had 96dB dynamic
range:

http://www.picotech.com/applications/resolution.html

And there USB based 12-bit versions have 72dB rather than the 80dB of
the parallel port versions. I expect they will dump the parallel ports
eventually.

This is a shame. The 16-bit unit is killer for low frequency/audio
amplifier testing and general spectrum analysis. The FFT functions on
8-bit fast DSOs from Tek and Agilent are of limited usefulness due to
meager 70dB range (with averaging).

I have been communicating with Pico to try to encourage them to keep the
16-bit or develop another one. They haven't been very responsive.

I will email the Cleverscope and notifiy them that they might consider
filling the opening Pico is leaving.



--
Good day!

________________________________________
Christopher R. Carlen
Principal Laser&Electronics Technologist
Sandia National Laboratories CA USA
[email protected]
NOTE, delete texts: "RemoveThis" and
"BOGUS" from email address to reply.

Well, it won't fit in your "under $1500" budget, but HP/Agilent for
many years has been making a 23-bit 20Ms/s card. It's not necessarily
useful to 23 bits, but even by today's standards, the distortion and
spur performance isn't too shabby, and was certainly cutting-edge when
it was introduced. And in a stand-alone instrument, the HP/Agilent
89410, especially those made around 2001 and later, should give you
pretty nice performance out to 10MHz. I can "see" signals 120dB below
full scale with a dB or so accuracy with mine, if there aren't also big
signals that put distortion products on top of them. There are a very
few spurs that keep you from getting to that low a level at every
frequency, but they are pretty low amplitude and few in number. (We'd
all love to have 120dB of spur-and-distortion-free dynamic range in a
10MHz bandwidth analyzer with general-purpose inputs, but it's not
likely to happen this year...)

Cheers,
Tom

 

[[email protected]]

Hi:

Picotech seems to be the only supplier of these in low cost <$1500 flavors.

But they are discontinuing their 16-bit version which had 96dB dynamic
range:

http://www.picotech.com/applications/resolution.html

And there USB based 12-bit versions have 72dB rather than the 80dB of
the parallel port versions. I expect they will dump the parallel ports
eventually.

This is a shame. The 16-bit unit is killer for low frequency/audio
amplifier testing and general spectrum analysis. The FFT functions on
8-bit fast DSOs from Tek and Agilent are of limited usefulness due to
meager 70dB range (with averaging).

I have been communicating with Pico to try to encourage them to keep the
16-bit or develop another one. They haven't been very responsive.

I will email the Cleverscope and notifiy them that they might consider
filling the opening Pico is leaving.



--
Good day!

________________________________________
Christopher R. Carlen
Principal Laser&Electronics Technologist
Sandia National Laboratories CA USA
[email protected]
NOTE, delete texts: "RemoveThis" and
"BOGUS" from email address to reply.

You can get the HP3562A used for under a grand. It is 14 bits and
100khz. It has GPIB to offload the data.

 

[Tom Bruhns]

You can get the HP3562A used for under a grand. It is 14 bits and
100khz. It has GPIB to offload the data.

Should note it's 100kHz bandwidth; sampling is faster. Of course, it's
also BIG and HEAVY (and if something goes wrong inside, it may not be
easy to fix).

 

[[email protected]]

Should note it's 100kHz bandwidth; sampling is faster. Of course, it's
also BIG and HEAVY (and if something goes wrong inside, it may not be
easy to fix).

It has a self-check, which makes the used purchase safer. The big
advantage to the 3562 is the synchromized sine source. No edge effects,
i.e. windowing errors. Big? You bet. ;-)

 

[Fred Bartoli]

[email protected] a écrit :

It has a self-check, which makes the used purchase safer. The big
advantage to the 3562 is the synchromized sine source. No edge effects,
i.e. windowing errors. Big? You bet. ;-)

I do have a 3563A which is the 16bit that followed the 3562A. Big and
noisy (fan) but excellent.

The 3562A has service manuals available but I couldn't find the 3563A ones.

 

[Tom Bruhns]

[email protected] a écrit :

I do have a 3563A which is the 16bit that followed the 3562A. Big and
noisy (fan) but excellent.

The 3562A has service manuals available but I couldn't find the 3563A ones.

Gee, Fred, I'm curious where you found a 16 bit 3563A ... ;-)

Cheers,
Tom

 

[[email protected]]

[email protected] a écrit :

I do have a 3563A which is the 16bit that followed the 3562A. Big and
noisy (fan) but excellent.

The 3562A has service manuals available but I couldn't find the 3563A ones.

Are there 3562 manuals on line?

 

[Fred Bartoli]

[email protected] a écrit :

Are there 3562 manuals on line?

I have them in case you can't find them, but I guess I got them either
from the agilent web site, either from their ftp.

 

[[email protected]]

[email protected] a écrit :

I have them in case you can't find them, but I guess I got them either
from the agilent web site, either from their ftp.

ftp://ftp.agilent.com/pub/manuals/
I found them. Thanks.

 

[vasile]

Well, it won't fit in your "under $1500" budget, but HP/Agilent for
many years has been making a 23-bit 20Ms/s card. It's not necessarily
useful to 23 bits, but even by today's standards, the distortion and
spur performance isn't too shabby, and was certainly cutting-edge when
it was introduced. And in a stand-alone instrument, the HP/Agilent
89410, especially those made around 2001 and later, should give you
pretty nice performance out to 10MHz. I can "see" signals 120dB below
full scale with a dB or so accuracy with mine

Hi Tom,
Did you have the curiosity of checking exactly the accuracy ?
Below 100dB is quite difficult to claim 1dB accuracy, even with a
45.000$ VNA or spectrum analyzer.

greetings,
Vasile

 

[Tom Bruhns]

Hi Tom,
Did you have the curiosity of checking exactly the accuracy ?
Below 100dB is quite difficult to claim 1dB accuracy, even with a
45.000$ VNA or spectrum analyzer.

greetings,
Vasile

Hi Vasile,

Well, yes, it was a bit more than idle curiosity. The linearity
of the ones with new ADC boards is generally quite good, noticably
better than the ones with the older boards, and those weren't bad at
all. Linearity to that level is not guaranteed, though. As you say,
it's not trivial to test.

Cheers,
Tom

 

[joseph2k]

I wonder if picotech ever fixed the glaring bugs in their software?

[edit discouraging story]


Bummer. Now I'm disinclined to buy one.

Any other experiences out there?

How about a different approach? semi-pro and pro audio offers some
interesting prospects, such as 10 channels at 24 bits and 192 ksamples /s.
requires firewire/1394 or usb2. start with RME/hammerfall please.

 

[Tom Bruhns]

Chris Carlen wrote:
Hi:
Picotech seems to be the only supplier of these in low cost <$1500
flavors.
But they are discontinuing their 16-bit version which had 96dB dynamic
range:
http://www.picotech.com/applications/resolution.html
And there USB based 12-bit versions have 72dB rather than the 80dB of
the parallel port versions. I expect they will dump the parallel ports
eventually.
This is a shame. The 16-bit unit is killer for low frequency/audio
amplifier testing and general spectrum analysis. The FFT functions on
8-bit fast DSOs from Tek and Agilent are of limited usefulness due to
meager 70dB range (with averaging).
I wonder if picotech ever fixed the glaring bugs in their software?

[edit discouraging story]

Bummer. Now I'm disinclined to buy one.

Any other experiences out there?How about a different approach? semi-pro and pro audio offers some

interesting prospects, such as 10 channels at 24 bits and 192 ksamples /s.
requires firewire/1394 or usb2. start with RME/hammerfall please.

One thing to be a little careful about with cards that are designed to
digitize audio is that they may use ADCs which indeed output 192k
samples per second, but which have internal digital filters which will
NOT allow response beyond 1/4 the output sample rate, or thereabouts.
If the design of the board has limits in the analog signal path, you
may be able to bypass that, but it will be difficult to deal with an
ADC like that. In doing a survey of ADCs for such an application, I
found more than one that was unacceptable for that reason. I believe a
few also have highpass filters that would prevent them from going to
DC, and in any event you might have to hack the software to disable
such a filter. If you want a highpass, it's nice to do it digitally,
because you can insure zero offset voltage, and many high-end audio
ADCs have at least the ability to do it in their digital processing.
(Practically all audio ADCs these days are delta-sigma type, with a lot
of digital filtering and decimation going on inside.)

Cheers,
Tom

 

[Mike Monett]

[...snip good info]

(Practically all audio ADCs these days are delta-sigma type, with a lot
of digital filtering and decimation going on inside.)

Cheers,
Tom

Can you tell us which boards had response to DC?

Which ones would you recommend for an inexpensive low-end pc scope?

Regards,

Mike Monett

 

[Tom Bruhns]

[...snip good info]

(Practically all audio ADCs these days are delta-sigma type, with a lot
of digital filtering and decimation going on inside.)

Cheers,
Tom

Can you tell us which boards had response to DC?

Which ones would you recommend for an inexpensive low-end pc scope?

Hi Mike,

Sorry if I wasn't clear about that. I was doing a survey (and not a
terribly complete one at that) of high resolution ADC parts that would
be useful in a digitizer that went to at least 80kHz bandwidth. I
can't tell you about any of the boards; I don't have info on what ADCs
they actually used. There may be good reasons to sample audio faster
than 44.1ks/s, but extending the digitized bandwidth much beyond 20kHz
is probably not very high on the list.

Cheers,
Tom

 

[John Devereux]

[...snip good info]

(Practically all audio ADCs these days are delta-sigma type, with a lot
of digital filtering and decimation going on inside.)

Cheers,
Tom

Can you tell us which boards had response to DC?

Which ones would you recommend for an inexpensive low-end pc scope?

Hi Mike,

Sorry if I wasn't clear about that. I was doing a survey (and not a
terribly complete one at that) of high resolution ADC parts that would
be useful in a digitizer that went to at least 80kHz bandwidth. I
can't tell you about any of the boards; I don't have info on what ADCs
they actually used. There may be good reasons to sample audio faster
than 44.1ks/s, but extending the digitized bandwidth much beyond 20kHz
is probably not very high on the list.

I would love to make a "scope" based on something like the
AD7660. It's a 24 bit 2.5MHz sigma delta ADC
<http://www.analog.com/en/prod/0,,AD7760,00.html>.

I was thinking

- USB powered
- buffer data in local SDRAM
- Hi-speed USB interface
- local SDRAM chip to buffer samples
- *all* samples streamed to controller PC
- PC does post processing for "triggering", averaging, spectrum analysis