There is also, discussed here, a survey of available references from
1960-1980s favored 10V at least in the mind of the folks at NIST:
https://www.gpo.gov/fdsys/pkg/GOVPUB-C13-2c2d0649085cc34834a8f42deaad328e/pdf/GOVPUB-C13-2c2d0649085cc34834a8f42deaad328e.pdf
So even if not true by the 1980s, the data generated by then aged, and
well characterized 10V references established the 10V 73x Fluke style
reference as a defacto standard. Tie that to Dr Frank's description of
the evolution of instruments and practical issues of designing around
'decades' gelled 10V into what is today.
On 3/9/2016 1:54 AM, Joseph Gray wrote:
Frank,
Thanks for the info. Do you have a link to the EEVblog discusison on
this? If not, possibly some search terms to narrow it down (10VDC is
too generic).
Joe Gray
W5JG
On Tue, Mar 8, 2016 at 4:47 PM, Frank Stellmach
<[email protected]> wrote:
Hi Joe,
yes, there has been a longer discussion on eevblog a few years ago..
interesting explanations..
Here's mine:
Originally, the Weston Standard Cells had an odd value of 1.01865V. This was
transferred to other values by KV dividers. These dividers were easily built
in decades, but maybe that did not prefer 10V, yet.
Analog meters at that time also had no preference, as they had several
overlapping ranges, sequenced like 1-3-10, or 1-2-5-10.
When more precise DVMs with higher resolution were built in the 1960ties,
like the Fluke Differential DVMs, as for example the 883A, 893A, and so on,
they got decimal ranges, as a necessity for cascading.
HP also designed several standards and differential DVMs having 9.9999X as
F.S.
Also, digital counters and early digital DVM, being based on such counters,
naturally had a F.S. like 9.999.
You can often find in the catalogues of that era, that digital or
differential DVM with a F.S. of 11V or 12V were described as 10V instruments
with 10% or 20% of Overrange Capability, or so.
So there was a necessity to have as a reference these Cardinal Points like
100mV, 1V, 10V, 100V, 1kV, with 10V being the most stable and easiest one to
realize.
And that lasts until today, although a direct calibration on the 6.9.. 7.2V
of zener elements like the LTZ1000 or LTFLU would be much more stable and
more precise than the 10V from a 732B.
Frank
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Best Wishes,
Marv
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