w2aew | #227: Vintage Tech: Fluke 881A Differential Voltmeter Introduction @w2aew | Uploaded January 2016 | Updated October 2024, 5 hours ago.
A brief look at the operation of a 50+ year old piece of vintage test and measurement equipment - the Fluke 881A Differential Voltmeter. Surprisingly, it is still very close to being "in-spec", at least on the one range demonstrated here. It uses a precision 0-11V reference that incorporates a Kelvin_Varley voltage divider. More information about a Kelvin-Varley divider can be found here:
en.wikipedia.org/wiki/Kelvin%E2%80%93Varley_divider
I thought that Dave Jones at EEVBlog did a video on the Kelvin-Varley, but it looks like he did talk about it in this video, bookmarked about about the right spot:
youtube.com/watch?v=onqsjDJq4I0&feature=youtu.be&t=1572
I did however find this video:
youtube.com/watch?v=JYsvo_jIR4M