[volt-nuts] 10VDC

[Frank Stellmach]

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