September (metrological) harvest. - Page 1
Forum section: electronics / general

author: Alex Nikitin
author_rank: Super Contributor
timestamp: September 29, 2021, 02:53:28 pm
content: This lot has arrived from across the pond in the last couple of days. The three SR1010 (1R, 10K, 100K) seems to be in a good shape, the Fluke is in an unknown condition, soon will find time to check it and see if it can make a nice pair to my 731B.CheersAlexP.S. I've asked IET Labs for the price of a couple of shorting bars. From the answer it looks like they make bars from solid gold. Certainly gold plated solid silver bars should be much cheaper.

author: dietert1
author_rank: Super Contributor
timestamp: September 29, 2021, 05:29:17 pm
content: The bars are a nice DIY project. Get some copper beams with 3 x 15 mm cross section from ebay, drill the holes, clean it and coat it in a bath. I remember 20 years ago applying gold to brass parts of an old clock and they still look nice. I would start with the short bars needed to make a minimum Hamon divider.Some time ago i tried to use short jumpers made of 10 mm² copper cable with lugs, but that didn't work very well.Regards, Dieter

author: Kosmic
author_rank: Super Contributor
timestamp: September 29, 2021, 06:16:51 pm
content: Quote from: dietert1 on September 29, 2021, 05:29:17 pmProbably not a good idea to apply gold directly on copper.From wikipedia (https://en.wikipedia.org/wiki/Gold_plating)Quote

author: Kosmic
author_rank: Super Contributor
timestamp: September 29, 2021, 06:20:13 pm
content: Quote from: Alex Nikitin on September 29, 2021, 02:53:28 pmIf you find a simple solution, let me know. I also need them and I don't really feel like finding someone to mill an identical copy. I was thinking to simply find the biggest solid copper wire I could find, bind it into shape and 3d print some handles.

author: doktor pyta
author_rank: Frequent Contributor
timestamp: September 29, 2021, 08:18:35 pm
content: My DIY shorting bars probably had too thin gold layer.https://www.eevblog.com/forum/metrology/esi-resitance-standard-sr1010-and-standard-resistor-sr104/msg1777625/#msg1777625

author: antintedo
author_rank: Contributor
timestamp: September 29, 2021, 08:33:42 pm
content: Quote from: Kosmic on September 29, 2021, 06:16:51 pmDepends on the gold thickness. 1um layer should slow down diffusion enough - see attached paper.Because binding posts rub directly on the plated surface, you probably would need hard gold plating or much thicker layer to protect those areas.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: September 29, 2021, 09:45:17 pm
content: Well, I've tried to check the condition of the 100K SR1010, as it has the table of tolerances from 1988. At the moment I cannot measure the absolute resistance accurately enough, but I've decided to try to measure the relative deviations. So I've applied 12V (more accurately, 11.99978V, so I could stay in the 10V range for control) to the ends of the chain (from the Keithley 263 which appears to be stable inside 1ppm over the time of measurements) and measured the voltage across each resistor for both polarities of voltage from the Keithley , I've used one of Keithley 2015 on 1V range, with averaging, the difference between results for two polarities was about 2-3ppm, and I took the average value from two measurements. The second 2015 was used to monitor the voltage applied.The measured relative deviations were inside +2.5/-2 ppm range compared to the original table. Meaning, for example, the difference between R1 and R7 was 3ppm in the original table and I've measured 3ppm difference, but between R1 and R4 the table gave 3.5ppm and I've measured 6ppm , so +2.5ppm compared to the table (that was the largest deviation to one side and - 2ppm was the largest in other direction. I would estimate that the deviations are on par with the errors of my measuring setup.Looks like the 100K unit survived quite well. I will try to do the same trick with 10K unit (though it has no tablebut appears OK on the first check and I have the Fluke 742A-10K to do a direct comparison), however for 1 Ohm unit I would need a better setup and bars, if I want to use it fully. It has a table but no date or other references on it. If I believe that table, the deviations of individual resistors are from -13ppm to -35ppm.CheersAlex