Nice made.
A Kelvin Varley devider is a total different animal als a resistor box or decade box.
Building one yourself is not a simple thing.
You use a resistor box or resistor decade just like you could use a potentiometer but with more resolution ( getting a 1M potentiometer at 1 Ohm step is not possible, even using a 10K ) and if saves the trouble of disconnecting it and then measure it. What in many cases is not a problem but in others it is. Like using it as an D/Q extention in bridge measurements. It is also more save, you can not so easy by accident zero it or get a to low resistance,
A KV is used as voltage divider for ratio measurements. You feed it with, or instance 10V and you can dial the output. Its an inginius system of switching while bridging resistors to keep a constant impedance. They are also terrible expensive, in the order of 15K dollar or so. You can not use them as resistorbox.
The ESI resistor decades or IET, or GenRad ( GR) are precision boxes, they are used for bridge measurements, precision measurements, calibration ect, not to hook it up in a schematic as feedback resistor to find the right value ( allthoug you can use them for that too)
I have bought a GR at a HAM fair for 10 euro that is from the 30's. Massive switched, wirewound resistors. Whitout a cabinet. Made one for it. Put a metal liner in it a few weeks a go to hield it. At home after the fair, I hooked it up to a 7,5 digit meter and it was after 80 years still within specs.
Allmost creepy
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
Since I have one, i must say, i use it a lot. More then my two KV dividers ( a fluke and a ESI). They are coupled to Vrefs ( a Fluke 332, homebrew 10V, a Philips and 3 other Flukes) i use two as a test. If i get strange results i can test the deviders, reference or meter to calibrate. Like last time I found a common mode problem. The meter to clibrate looked non lineair, but it also could be the monitor-meter or KV. Then as test it showed excact the same prolem using the other KV. Also using an other monitor or other Vref.
So the problem was in the meter or something else. But a monitor meter on the output showed the same roblem. Switched of all power exect the reference, monitor and meter to calibrate and the problem was gone. Still must fin the source of the prolem. So by having things double you can check and anlyse problems.
But that had nothing to do with a resistorbox or the "real men resistor box" from the first pos that , i think, is just a passive dummyload. Replaced today by electronic loads.