10:1 Hamon Divider Question - Page 1
Forum section: electronics / general

author: VintageNut
author_rank: Frequent Contributor
timestamp: January 11, 2023, 03:19:19 pm
content: I have an old ESI SR1050 that is 10 megohms per step. There are 11 resistors. I have not found any application note that shows using the 11th resistor. I am asking the forum here if anyone knows of a measurement that utilizes all 11 resistors at the same time.

author: MK
author_rank: Regular Contributor
timestamp: January 11, 2023, 09:21:05 pm
content: On the ESI website there are some application notes that show how to use the resistors for various division ratios, cannot remember where on the site though.

author: VintageNut
author_rank: Frequent Contributor
timestamp: January 12, 2023, 02:12:13 am
content: Those are in the manual which I have. I do not see any configuration using all 11 resistors.

author: trobbins
author_rank: Frequent Contributor
timestamp: January 12, 2023, 03:25:19 am
content: Perhaps it is a spare part, given the risk of damage.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: January 12, 2023, 02:37:44 pm
content: Let's say you wanted to turn it into a Kelvin-Varley divider. You need 11 resistors because the next deck has to cross two. Without the 11 th resistor you'd only have 9 steps!

author: Harfner
author_rank: Contributor
timestamp: January 13, 2023, 03:24:34 pm
content: It seems that the original article "A 1-100 Ω build-up resistor for the calibration of standard resistors" in Journal of Scientific Instruments, Volume 31, Number 12 from 1954 by B V Hamon did suggest 11 resistors. People are copying a schematic from that article showing 11 resistors.I can not access that article, since I do not work in a research institute. Could somebody look at the original article and shed some light on the mystery?

author: donlisms
author_rank: Frequent Contributor
timestamp: January 14, 2023, 03:00:51 pm
content: The article is more of an overview in some ways; Hamon apparently preferred not to delve into all the details, but he gives enough to get the idea of things. The primary focus is a reminder that if the resistors are each accurate to 10e-4, the ratios formed between series and parallel groups is of the order 10e-8 or better... which I guess is pretty good, in theory. (A nice place to start.) Getting there in real life meant using tetrajunctions (not by name, but by description, i.e. "such that three of the leads are symmetrical with respect to the fourth") and using balancing resistors in the paralleling connections.So for the 11, he does point out that if you have 11 resistors, you can easily create an accurate 10:1 divider, and use that as a precise ratio in one side of a bridge -- for example, a Kelvin bridge being used to scale measurements up or down by 10, with calibration against a 1 ohm standard, and measurements good to 10e-4 ohms or so.To verify the divider, each resistor can be compared against the series-parallel combination of nine of the others. You're only using ten of the resistors during such a comparison, but you can check each of the eleven against the (most of) the others this way. This can tell you what your 10:1 ratio really is.He describes a sort of "compound substitution" method, using the bridge to find the difference between one resistor and a series-parallel of nine others, and then the difference between an unknown and the nine, to find the unknown relative to divider. Then use the divider calibration against a 10R or 0.1R standard, and you have a measurement of the unknown relative to that standard.He mentions that there was nothing else to calibrate the original version against, only against itself used in different ways. They used the 10:1 divider technique to measure 10 and 100 ohm resistors against a 1 ohm standard to better than 0.4ppm, which corrections for heating bring the numbers down to 0.1ppm.He writes quite a bit about the design and construction of the (Leeds and Northrup version of) the resistor, with every detail considered. It is an SR1010/50 in a small, round box. I would use the word "beautiful" in describing its design and implementation.He does not talk about using 3 in series and 3 in parallel to make a 10:1 divider, one of the more common techniques associated with his name today. There is no mention of using the buildup resistor as part of a Kelvin-Varley divider. I'm not sure SR1050 gives enough connectivity to be used that way, and there would be some complications using SR1010 or Hamon style dividers this way, because if your decade ratios are not 5:1 you need to tinker with a corrective parallel resistance and such. But I guess you could do it.There are a lot of papers from the early days that reveal much brain-power for getting high precision resistance measurements in the absence of 3458's or whatever. Clearly some people have more sophisticated and more expensive techniques these days, but the purity and simplicity of the older techniques means people can still use them and get good results. Wenner and Thomas in particular wrote a lot of good and interesting stuff.

author: Echo88
author_rank: Frequent Contributor
timestamp: January 14, 2023, 09:09:08 pm
content: @Harfner:https://sci-hub.hkvisa.net/10.1088/0950-7671/31/12/307