HP 3458 DVM
© Brooke Clarke 2009Photo
Background
DOA
Options
Patents
History
Links
Background
During my career as an engineer
I
specified this meter into automatic test systems and wrote
code to
control them. The key feature is that they are very
accurate. For example when the definition of the Volt
changed we
had some instruments with a sticker saying that they measured
the new
Volt. When comparing those with the no sticker meters
the
difference was the difference in the Volt definition.
Quite
impressive.
HP Journal for April 1989 - describes the new developments.
HP Journal for April 1989 - describes the new developments.
DOA
The manual does not have the
details
necessary to troubleshoot down to the component level.
They use
board level replacement to fix problems.
This one came from eBay and was
sold
untested and marked "Strapped
for
220 VAC". It's a very simple thing (rear panel switches)
to set
it for 120 VAC. But on power up there is a single beep,
the
display shows "testing RAM"
and all the icons anpixels are on, then quickly changes to
ISOLATOR
DTACK and locks up there. Pressing Blue and or Error
either at
the same time or in sequence does nothing. The error
message is
associated with the A5 Outguard Controller board.
Pressing Blue then Clear or Blue + Clear has no effect on the error message.
Disconnecting and reconnecting all the electrical and FO joints had no effect.
There is a smell like hot phenolic but so far havent found where it's coming from.
Pressing Blue then Clear or Blue + Clear has no effect on the error message.
Disconnecting and reconnecting all the electrical and FO joints had no effect.
There is a smell like hot phenolic but so far havent found where it's coming from.
Options
My board is
-3458-66505 Rev C and is the non option 001
version. The
option 1 board
would be 03458-66515. Option 001 is extended reading
memory and
probably consists of filling positions U122, U123, U124, U125
with RAM
chips and relocating JM600 (just a guess, not yet
analyzed). The
Outguard Power Supply board (under bottom cover) shows the two
+5 VDC
test points to be right in the middle of their allowed
range. The
+15 VDC test point (P3 red wire) reads 14.0 VDC but there
doesn't seem
to be a spec for it.
Option 002 is marked on the rear panel label. That's the high stability Voltage reference (4 ppm/year).
I have on a bookshelf somewhere the Waveform Analysis Library (03458-80002). The 3458 can work like a sampling scope but the data comes out in a strange (interleaved) pattern and needs to be put back into time order in order to get a "scope" like display on your computer.
Option 002 is marked on the rear panel label. That's the high stability Voltage reference (4 ppm/year).
I have on a bookshelf somewhere the Waveform Analysis Library (03458-80002). The 3458 can work like a sampling scope but the data comes out in a strange (interleaved) pattern and needs to be put back into time order in order to get a "scope" like display on your computer.
Patents
These are patents that may be related to the HP 3458A.4357600 Multislope converter and conversion technique, James Ressmeyer, Joe E. Marriott, Lawrence T. Jones (Hewlett Packard), Nov 2, 1982, 341/129
4766401 Coaxial switching system with switched shields and crosstalk suppression, David P. Kjosness, Joe E. Marriott (Hewlett Packard), Aug 23, 1988, 333/12; 333/262; 335/5
4951053 Method and apparatus for switching currents into the summing node of an Integrating Analog-Digital Converter, Lawrence A. DesJardin, Wayne C. Goeke (Hewlett Packard), Aug 21, 1990, 341/136; 341/135; 341/155; 341/172
5200752 Integrating analog to digital converter run-up method and system, Wayne C. Goeke (Hewlett Packard), Apr 6, 1993, 341/168; 341/166
5117227 Continuously integrating high-resolution analog-to-digital converter, Wayne C. Goeke (Hewlett Packard), May 26, 1992, 341/166; 341/156
History
This account provided by Dr. Frank and is
provided with
his authorization. First appeared on the Volts Nuts list
server.
| I also picked one up, a
mixed
one, ie old analogue PCB from the 90's and a younger
processor board
from 2001 (perhaps replaced due to SRAM battery
discharge). Cost me
about 3k instead of of 8k new, and its working
perfectly - but stable
environmental temperature conditions are required,
thats the weak point
of the design. Maybe its an old design, but currently, no other DMM or calibrator can beat it essentially in certain parameters. It has got the best (differential) linearity, over Keithley 2002, Fluke 8508A, Datron 1281, Fluke 57xx and even the Primary Ratio standard 720A! Only the JJ array can test its linearity! OK, the 3458A's internal references are not that stable, but it is not intended as a secondary volt or ohm standard. For that you need additionally something like a 732B and a SR 104, or the quantum standards, respectively. But all others of the above mentioned, newer DMMs are not much better. For DCV, the 3458A obviously has been designed for a very broad temperature range of 0..55°C (military use??), which gives an internal temp of at least up to 80°C in a rack mount. Placing its internal volt and ohm standards in a lower and more stable environment would have been better, but then, it could not have been a DMM-in-one-box. So the internal LTZ1000A reference has to be running on 90°C. If powerered constantly, this gives at least 20 times higher drift rates over time compared to a Fluke 7000A, which is running on 45°C. Other DMM are specified for metrological temp. range and have certainly slightly better drift rates (two times). I have set (pimped) the LTZ to about 55°C for lower drift. The HV divider cannot be corrected for power dissipation effects, so the 1000V range is quite mediocre. I have built my own 100:1 Hammond type divider (~ 752A) to get around 1ppm for 1000V. The ohm ranges obviously is its weakest mode. It relies on an elder hermetically sealed Vishay resistor, with high time and temp. drift, and additionally the resistor is exposed to the strong internal temperature variations. Today, by using a selected VHP202Z resistor, one might improve time drift to <1ppm/year and stability (with respect to temperature) to < 0.2ppm over the complete "metrological" ambient temp range. Additionally, its ohms range resistors are very sensitive to temperature changes. But it is possible by using it in absolutely stable amb. temp. conditions (+/- 0.2K), to make 10kOhm measurements / transfers on sub ppm stability level. Currently, I'm working on external 10k standard resistors; but still in discussion with Vishay. Report will follow. ACV is also umparalleled by other DMMs, due to its (patented?) digitizing algorithms, and this can be further improved by Swerleins Algorithm. So I think, only Flukes AC standard 792A is "better", if using standard electronics. So my advice, get one used 3458A, it's simply a nice and ultra precise box, and build yourself some standards which you would need also if you got a newer DMM. Btw.: A good, absolute calibration is nearly impossible to acquire for us amateurs. Even Fluke and agilent obviously offer 2nd grade calibrations only. Frank |
Links
HP Journal - April 1989 the 3458A is the Cover FeatureK04BB - HP 3458A Precision Digital Multimeter - two different HP calibration options
Volt Nuts mailing list
HP/Agilent mailing list
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