I like the 5200A for a good stable unit up to 110 volts but if you go above
that you would be better off with a 5100B which will do 1100 volts.

On Tue, Jul 8, 2014 at 6:46 PM, J. L. Trantham jltran@att.net wrote:

--
John Phillips

John,

Thanks for the reply.  I have both of those.

What I'm thinking about is a measurement standard.  That is, how do I know
that my 'standards' are accurate?

That brings to mind the 'thermal converter' issue.  The 8506A apparently
uses a 'thermal converter' as part of its measurement process.  The
individual A55 Thermal Converters can be used for their various ranges but
might be more expensive if you collect all of them.

So, the question is how would you go about 'proving' that your reference is
indeed accurate?  As best I can tell, this has to do with comparing it to
some DC reference by virtue of an RMS (thermal, as best I can tell)
comparison.

Joe

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of John Phillips
Sent: Tuesday, July 08, 2014 8:57 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] AC Voltage Measurement Standards

I like the 5200A for a good stable unit up to 110 volts but if you go above
that you would be better off with a 5100B which will do 1100 volts.

On Tue, Jul 8, 2014 at 6:46 PM, J. L. Trantham jltran@att.net wrote:

--
John Phillips

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Joe,

I have the above listed models. My opinion of the 540B is that it requires
a lot of work. Reading the manual, it suggests swapping cables for
repeatability to get a good reading.

It originally shipped with a mercury cell for the galvanometer so you may
get a D sized dead/leaking battery. It also has a large Ni-Cd pack for
operation since it is not recommended for use while plugged in. There is no
proper battery charging circuit so you will have to monitor the charge
time. Also, there appears to have been two versions of the plug-in unit.
They are either A54-1 or A54-2. I cannot tell you the difference between
the two. I think that the A54-2 had better input protection.

Hopefully you can get one with a good thermal element that has not been
blown out. There is a procedure on EEVblog for determining if the thermal
element is not damaged.
I found a link a few months ago where Transmille was using the input port
for the A55 thermal converters as an output line. They connected the output
to different 8.5 digit multimeters to characterize an AC source.

My 8506A's are very nice. They are spec'd to 1Mhz and make a good second
7.5 digit DC meter too. Unfortunately, you cannot do AC current
measurements without using external shunts like the A45 series.

I have two different A55 thermal converters, but they have not been
thoroughly tested. I would recommend getting the Ballantine 1395A/B thermal
converters as they appear to be better supported by cal labs. I think
Ballantine still sells them and will do repairs and calibrations.

My other favorite is the Fluke 8920A. I think it is a good meter. It's 3.5
digit display is augmented by a DC analog output that you can connect to an
external meter. The 8920A is recommended for calibrating the 5100B series
wideband output.

Another potential AC measurement standard would be the Datron/Wavetek 4920
or 4950 reference standards. The cost to calibrate from Fluke is
astronomical though. You can look up the pricing on their website to see
what they charge. $3K-4K if I remember correctly.

Before I sent my 3458A in for calibration, the NVRAM was changed and I
performed the SCAL using my 5100B and 8920A. I was able to get the cal to
pass and was very surprised when Gary Bierman told me that all tests passed
during calibration.

I think you should consider getting both the 8506A and 8920A. Pick up a set
of shunts whenever you can get a good deal.

Todd

On Tue, Jul 8, 2014 at 9:46 PM, J. L. Trantham jltran@att.net wrote:

In my previous post I meant the Fluke A40/A40A series current shunts. The
A45 is the current transfer switch used between the A40A shunts and 540B
for quicker measurements.

Todd

On Tue, Jul 8, 2014 at 10:52 PM, Mitch Van Ochten <
mitch@vincentelectronics.com> wrote:

J. L. ,
I do not know what level you are willing to pay for. I do not work in a
real high end lab but we seem to get by with checking our secondary
standards with a 3458A before and after we send it to gary to be
calibrated. We use our 10 volts and 10K resistor to calibrate the 3458A
before we send it in and then after. We look at the before and after data
as well to come up with new values for the units. Comes down to using the
3458A as the primary standard filtered by our history. The different AC
measurement methods in statistical mode can give you a good idea where your
AC values really are.

I would like to know how that compares with what the extra hardware can do.

On Tue, Jul 8, 2014 at 7:52 PM, Mitch Van Ochten <
mitch@vincentelectronics.com> wrote:

--
John Phillips

J.L.,
it really depends on what level of accuracy you are looking for. The gold standard obviously is the Fluke 792A. That is probably not an option. The Fluke 8606 is more on the lower end side (dont get me wrong, compared to the 792A), it does not really bring much improvements compared to the 3458A operated in the AC SYNC mode, but maybe it is good enogh for what you want to do. In that range are also e.g. the R&S ac voltmeters, but their focus is more in the higher frequency area.
Very good accuracies are achieved by thermal converters (Ballantine...). You can do DC to AC comparison measurements with a few ppm accuracy. But measurements are slow, and you need a nanovolt meter.

I personally did the following: I got a Ballantine 1605A transfer voltmeter. This is comparable to the 792A in a way, except it was much cheaper. It is automatic, much easier to use than the Fluke 540 and goes up to I think 100MHz. This can be used for percision calibrations as a working standard. The calibration of this meter as well as others (e.g. the 3458A in its AC mode) I am doing with a set of thermal converters (0.5V to 100V). One of which (10V) has been externally calibrated up to 30MHz, cal of the others are derived from it. That way I am deriving everything from a very precisely (few ppm) calibrated 10V TVC. Overall, this saves cost on the calibration side, allows for high accuracy and measurement speed is good.

In message trinity-2e0df2e8-1978-44c0-8d7f-1248885e1b2e-1404906840284@3capp-gmx-bs72, acbern@gm
x.de writes:

And very stable surrounding temperature.

Thermal converters measure the heating caused by the electric energy
as a temperature increase over ambient temperature.

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