More thoughts on the 3458A
One thing that strikes me reading old 3458A product datasheet from HP is
that they stressed the high measurement speed, 100kHz @ 16 bit, but not
empasizing much the DC accuracy. Now, the 3458A remains state of the art in
DC accuracy / liearity, but for high speed measurements and of course
frequency, the 3458 is now nowhere near state of the art any more.
As Tom pointed out there is a lot of characterizing around the 3458 and
also a high trust from other manufaturers. For example I have a precision
SMU and the calibration procedure is explicitly and with detail, pointing
to the 3458.
On price: basic price was perhaps once set by development and materials
cost. But after 25 years, a sales department sets the price, to whatever
they think is most profitable....
In message CAFoWNwBDPPnjEF8gBsFWsFPCFc6qhG+dWG=oYEAhuGgU=wHXrw@mail.gmail.com
, Jan Fredriksson writes:
One thing that strikes me reading old 3458A product datasheet from HP is
that they stressed the high measurement speed, 100kHz @ 16 bit, but not
empasizing much the DC accuracy.
If I had no scruples at all, I would start digitizing audio using
two HP3558A's synchronized to a Cesium frequency standard, and
market it to the audio-homoepathy segment at prices you can not
even imagine :-)
Now, the 3458A remains state of the art in
DC accuracy / liearity, but for high speed measurements and of course
frequency, the 3458 is now nowhere near state of the art any more.
The biggest issue is that you cannot use an external sample-clock,
but only free-wheel the 3458A. NIST did modify a 3458A during
some of their J-J AC experiments, so they could synchronize the
sampling to the synthetic AC generated by the J-J.
I don't know how "state of the art" it is or isn't, you can obviously
buy chips which do 100 GS/s @ 16 bits these days, but my impression
is that they are nowhere near the HP3458A in absolute precision or
for that matter, reference stability.
The main limitation is that the HP3458A has very little RAM, so to
use the 100kHz sampling-rate, you need to download and run code
which can compress the samples in real-time, preferably into something
GPIB almost can keep up with. That is easier than it sounds, but
still a hazzle most people would prefer to be without.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
Poul-Henning Kamp wrote:
...
The main limitation is that the HP3458A has very little RAM, so to
use the 100kHz sampling-rate, you need to download and run code
which can compress the samples in real-time, preferably into something
GPIB almost can keep up with. That is easier than it sounds, but
still a hazzle most people would prefer to be without.
On the other hand, one could take the tack that John Seamons is
following with the HP5370A/B time interval/frequency counter, and
replace the CPU with something lower power, faster, and much more
capable... and with an ethernet interface. A Beagle Bone Black
SBC.
-Chuck Harris
In message 52E02644.6010002@erols.com, Chuck Harris writes:
Poul-Henning Kamp wrote:
...
The main limitation is that the HP3458A has very little RAM, so to
use the 100kHz sampling-rate, you need to download and run code
which can compress the samples in real-time, preferably into something
GPIB almost can keep up with. That is easier than it sounds, but
still a hazzle most people would prefer to be without.
On the other hand, one could take the tack that John Seamons is
following with the HP5370A/B time interval/frequency counter, and
replace the CPU with something lower power, faster, and much more
capable... and with an ethernet interface. A Beagle Bone Black
SBC.
The CPU is a 68k, there's plenty of power, it's just the ethernet
which is missing.
Yes, I have been thinking about such ideas, but my time is
limited...
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.