Is it possible to trim 0,1% resistor to 0.05% value? - Page 1
Forum section: electronics / general

author: 001
author_rank: Super Contributor
timestamp: September 05, 2018, 06:37:10 am
content: Is it possible to trim 0,1% resistor to 0.05% value with about 20ppm for a long time?Grinders, shunts, statistical tricks, etc?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 05, 2018, 06:48:34 am
content: Quote from: 001 on September 05, 2018, 06:37:10 amTrim with other 0.1% resistors in series and/or parallel

author: try
author_rank: Regular Contributor
timestamp: September 05, 2018, 09:25:15 am
content: Hi 001,Quote from: 001 on September 05, 2018, 06:37:10 amit depends on the resistor value that you left out.Try to trim 10M Ohm for instance.What is "with about 20ppm for a long time"?Do you mean 20ppm drift over "a long time"?Or do you rather mean trimming from 0,1% to 0,02% accuracy?You might consider mentioning more quantitative terms.

author: Wolfgang
author_rank: Super Contributor
timestamp: September 05, 2018, 05:18:40 pm
content: You may try, probably by the following method:- Buy a bunch of 0.01% resistors and screen them for initial tolerance (you have a 3458A, I suppose). Sort out the ones that do not have enough precision- Then, put them into a climate chamber and temp cycle them from 0 to a bit below their max. temp for a year.- Sort out the ones with too much tempco.- Redo the screening. What is still within 0.005% is probably safe.... ORjust buy them von Vishay right from the start. Probably a lot cheaper and you can start working with them tomorrow.

author: iMo
author_rank: Super Contributor
timestamp: September 05, 2018, 10:49:38 pm
content: Quote from: Wolfgang on September 05, 2018, 05:18:40 pmHow the Vishay does it then? Such an resistor must cost you an arm and a leg..

author: Wolfgang
author_rank: Super Contributor
timestamp: September 05, 2018, 11:01:40 pm
content: If you look at their datasheets they use laser trimming.For the 10ppm grades, I am dead sure that they use screening and aging as well.Measuring those is a challenge even for a 3458A. DC voltage precision with option 2 is 4ppm. Resistor precision is less than that, depending on value.Link to datasheet:http://www.vishaypg.com/docs/63146/vhp203.pdfI did not find a price for them. A 50ppm one is a few 10€ per piece, I guess the range for a 10ppm resistor is a few 100€.

author: Wolfgang
author_rank: Super Contributor
timestamp: September 05, 2018, 11:10:23 pm
content: Hi, I found a quote at Newark:https://www.newark.com/vishay/y60721k00000s0l/vhp203-1k0000-0-001/dp/51X5889a 10ppm 1K resistor costs about 100€ in single quantities. So its an arm and leg, but the rest stays intact.The question of the day here is: Which meter can measure this thing with a precision of 1ppm or less in (4-wire, of course) resistance mode ?

author: Vgkid
author_rank: Super Contributor
timestamp: September 05, 2018, 11:51:57 pm
content: If you want accuracy you will need a esi242d+ standard resistors(national metrology lab /primary standards lab certified) , or a dcc(direct current comparator)+ same standard resistors. I haven't looked into using a long scale dmm+ standard resistor method.

author: splin
author_rank: Frequent Contributor
timestamp: September 06, 2018, 03:16:48 am
content: Quote from: Wolfgang on September 05, 2018, 11:10:23 pmWrong question methinks - Newark aren't guaranteeing anything - when exactly was the resistor measured to 'within 10ppm' and how much may it have drifted by the time you receive it?

author: Brak
author_rank: Contributor
timestamp: September 06, 2018, 06:02:22 am
content: Applicable post by Edwin G. Pettis:Precision resistor specifications and definitions.https://www.eevblog.com/forum/metrology/precision-resistor-specifications-and-definitions/Brak

author: Wolfgang
author_rank: Super Contributor
timestamp: September 06, 2018, 08:21:03 am
content: ... they have a shelf life spec, and I suppose you will get a certificate when buying one of those.

author: macboy
author_rank: Super Contributor
timestamp: September 07, 2018, 03:25:06 pm
content: Quote from: 001 on September 05, 2018, 06:37:10 amSince you mentioned statistical tricks,If you simply wire upNof them in a series-parallel configuration, you get sqrt(1/N) of the error, so four resistors of 0.1% gives you 0.05%. This assumes a normal distribution of error around the nominal value.

author: mzzj
author_rank: Super Contributor
timestamp: September 07, 2018, 04:32:34 pm
content: Quote from: Wolfgang on September 05, 2018, 11:10:23 pmMost of the "serious" temperature calibration labs have toys to measure resistance to around 1ppm or better within limited resistance range.Fluke 1595, or various MI or ASL(isotech) bridges are the usual toys with accuracies in 0,2 to 0,02ppm range.http://mintl.com/productcategories/metrology/resistance-measurement/resistance-bridges/https://www.isotechna.com/Thermometry-Bridges-s/35.htmWe got two older Hart/Fluke 1590's that are good to about 1ppm. Reference resistor is almost another 1ppm, but if I really push the uncertainties I would probably end up at about 1ppm total. (not for 0,1 ohm resistor tough!)

author: 001
author_rank: Super Contributor
timestamp: September 08, 2018, 08:30:40 pm
content: from the internet "It's well known that the cheapest way to get an accurate resistor is to put many together; ten standard-grade metal film 10kΩ 1% resistors in parallel gives a 1kΩ resistor with a 0.3% tolerance for less money than a 0.5% part would cost."WHY?

author: feedback.loop
author_rank: Frequent Contributor
timestamp: September 08, 2018, 08:39:27 pm
content: Quote from: 001 on September 08, 2018, 08:30:40 pmAs macboy explained above, the error is sqrt(1/N), which in this case of 10 resistors of 1% will be 1/sqrt(10) ~= 1/3%This is a simplification of course. This is assuming that individual resistors have independent distribution of error, which is not really so if they come from the same batch or even the same manufacturer. There might be some systematic factor involved.

author: GigaJoe
author_rank: Frequent Contributor
timestamp: September 09, 2018, 06:15:20 pm
content: it works , if the value normally dispersed , from my practice not at all, mostly under. means for a set of 20 10K resistors, only 2-3 will above 10k , the rest below ...I'm usually building myself, trimming surface by filers, heating for couple days at +160 for oxidation, and many layers of conformal coating .....some low tempco ( like 25 -50 ppm) often has positive and negative tempco curve, in the same set (spin, roll, package, batch, etc) possible to combine resistors, for a significant TC elimination.

author: try
author_rank: Regular Contributor
timestamp: September 10, 2018, 02:34:46 pm
content: Hello 001,Quote from: 001 on September 08, 2018, 08:30:40 pmpricewise this is currently not true in my country.Each time you sum something up the outcome is converging against a normal distribution.This is obvious when looking at the formula for paralleling 10 resistors.A simple way to understand it is the following:Throw a dice once and write down the result.Repeat this procedure a 100 times. How often do certain numbers appear?Throw a dice two times, sum up the result.Repeat this procedure a 100 times. How often do certain numbers appear?Throw a three two times, sum up the result.Repeat this procedure a 100 times. How often do certain numbers appear?What happens with the sums?Go and count which sum appears how many times and plot that on a graph.By the way, if you ask questions in other threads you might consider answering people when they ask you.It's disappointing for people that spend time on your questions when you don't react anymore.Otherwise they might not take your questions seriously in the future and stop answering you.Regardstry

author: e61_phil
author_rank: Frequent Contributor
timestamp: September 12, 2018, 06:27:08 am
content: Quote from: Wolfgang on September 06, 2018, 08:21:03 amYou don't get a certificate for this resistors (normally). I paid ~70€ for a 10ppm tolerance VHP101.