what nist means is that a precision meter is not considered a standard. you
always measure against a true standard (732a, esi sr104...). nist does not mean
that as part of doing equipment calibration a 3458a cannot be used as aid. also
keep in mind nist has a different approach than a cal lab,
I am doing multiple 100 measurements simply to characterize the stability
of the 3458A and 732A units I just bought. After about 10 measurement sets
over 2 days I am seeing a variance of about .5 uV for the 10V output, or
0.05 ppm. However, the mean varies over a range of 10 uV, or 1 ppm. Does
I forgot to mention that I reduced the number of measurements to 100 per
set since I wasn't seeing much difference in the variance between 100 and
1000 measurements and the 1000 measurement per set takes too long.
Randy
On Wed, Aug 27, 2014 at 5:13 AM, Randy Evans randyevans2...@gmail.com
Fred,
The 3458A is 8.5 digits, which puts it into the standards category. They are
used as lab standards in many, many labs.
73,
Steve
WB0DBS
On Aug 27, 2014, at 12:08 AM, pa4...@gmail.com wrote:
Thanks, I did not new NIST has so much interesting information on their site.
I
well, what you do is to measure the stability of the 3458a. 1ppm drift though
sounds much as overall short term average variation if your temperature is
stable and your 3458a is always on. probably the temp is not stable, and that
is what you see, amongst potentially some other smaller drifts
Randy:
Something I had never tried to measure. As I have found out in the past
there is a lot of overhead going on in the meter during and after a
measurement.
In thinking about this I turned OFF the autozero AZERO and the time
for each SMPL was cut in half to around the estimated 16.66
I have included a link to an ~30-hour measurement run that I consistently do
that should give you some idea of expected measurement drift over time.
Virtually all of the measurement drift is due to the 3458A internal temperature
differences around the 7V reference caused by ambient temperature
The HP3458A and the Fluke 732A are on continuously and I do an ACAL at
least every few hours, or when the room temperature changes by more than 1
degree C. The total range of measurements is 10uV so the drift is +/-5uV,
or 0.5 ppm. The room temperature is not particularly stable and varies
over a
Don,
If I am reading your charts correctly, it looks like your system is cycling
over an 7 uV range over several days in summer, similar to what I am
seeing. I don't have air conditioning (Northern California) so I do get
some pretty good temperature variations from day to night, but less inside
Randy,
Sorry for the two graphs being at different scales so just be sure to readjust
your reference. I like to think in PPM terms so the first graph is +/- 5 PPM
for the whole gray plot area while the second is +/- 1 PPM. The most extreme
outliers on the first graph is +0.3 to -0.5 PPM so
hi randy,
the specified drift of the 3458a over your 38.1 to 40.3 (about 1k) is 1ppm +/-
allone in the 10v range. thats 10uv. in other ranges its worse.
unless your 732a is very bad (very unlikely), you measure mostly the 3458a
temp. drift. 1000nplc and 100 readings average do not make sense in
On 26/08/2014 16:05, Mike S wrote:
After some more research, I think I've answered some of my own
questions -
Tellurium copper is used for binding posts, not because it has any
special thermal or EMF mojo, but because it machines much better than
pure copper. And, I suppose, because it
As a non-scholar in metrology, I tend to want to simplify the results of an
academic debate to make the results of the debate useful to me. One thing
is clear from my web search, copper alloyed with Tellurium, or Beryllium,
still oxidizes, only at a slower rate. It appears that a big disadvantage
Hi all,
Over the last 6 months I have been steadily repairing a
faulty 5200A that I brought, it had numerous faults in the power supply
regulator and power amplifier boards that I have managed to repair with a
lot of difficulty as I do not have an extender board to operate the
Folks,
Had some correspondence with Fluke a while back regarding adjustment of the
752A Reference Divider. They no longer sell the 845AB Null Detector but
they have some suggestions on alternate meters to do the job. They also
make reference to zeroing the inputs of the detector, which has
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