What brand precision BMF resistor is this? What Can I Build? - Page 1
Forum section: electronics / general

author: denimdragon
author_rank: Regular Contributor
timestamp: March 26, 2024, 06:08:46 am
content: I had a datasheet on these but I have since then misplaced itDoes anyone know what brand this is? I recall that they had been boughtout by Vishay a while back. They are spec'd pretty good. I have tons,but only one value 3118 ohms. I would also love any suggestions ofwhat piece of precision test gear I could make. A nice voltage dividercomes to mind

author: denimdragon
author_rank: Regular Contributor
timestamp: March 26, 2024, 05:36:48 pm
content: So, no one who has viewed this thread, is familiar with thisresistor brand?Well, I have been logging them with my 34970A and my freshlyCal'D (yeap, I have been bitten by the v-n bug) 34401Aover a 6 hour period @ 24°C ±2°C (no RH yet, but the lab is locatedat the highest part of the house so...) and they have performed extremelywell (≅<1ppm/°C).Maybe I have posted this in the wrong forum. Mods, let me know.

author: Victorman222
author_rank: Regular Contributor
timestamp: March 26, 2024, 06:22:10 pm
content: My google-fu lead me to Wilbrecht ledco. Check out:https://web.archive.org/web/20120108085924/http://www.wilbrechtledco.com/produits/foil.htmlLuckily even the datasheets are archived.

author: trobbins
author_rank: Frequent Contributor
timestamp: March 27, 2024, 03:50:03 am
content: Hammon dividers and bridge always need good precision resistors, and you could go the next level and sort what you have for value and tempo.

author: donlisms
author_rank: Frequent Contributor
timestamp: March 27, 2024, 05:14:56 am
content: Three of them in series plus 646 ohms makes 10k. I don't know what that might mean, but it seems interesting.

author: denimdragon
author_rank: Regular Contributor
timestamp: March 27, 2024, 11:38:23 am
content: Quote from: trobbins on March 27, 2024, 03:50:03 amThis is what had in mind. I started logging them a couple of days agowith one of my HP 34970A 6 resistors at a time. My question here is,how long should I monitor them to get a reasonable estimation? Shouldit be for 1K hours or can I get away with less? According to the datasheet, the TC is ±2.5ppm.

author: trobbins
author_rank: Frequent Contributor
timestamp: March 27, 2024, 12:19:27 pm
content: I would have thought just some simplified binning for starters based on a gross temp shift of say 5 degC to see what distribution of tempco's occur. If you easily identify pos and neg levels of tempco then you could match pairs of similar pos and neg tempco's, as what Fluke (and I guess many others) did.

author: denimdragon
author_rank: Regular Contributor
timestamp: March 27, 2024, 01:49:45 pm
content: Quote from: trobbins on March 27, 2024, 12:19:27 pmYes, matching the TC drift direction is the most critical aspect. I haveabout 400 of this particular value so I should be able to come up withsome nice matches. I'm setting up the modules for 4W measurementsnow so I can get the process going. These 34970As are so awesomefor this process. They are so underrated.I also need the exact datasheet for this "YT" series. I have datasheetsfor the WA WB & WQ WT, but no YT.

author: Victorman222
author_rank: Regular Contributor
timestamp: March 27, 2024, 06:33:06 pm
content: Quote from: denimdragon on March 27, 2024, 01:49:45 pmThese resistors are probably WA or WB or their predecessors as they have same marking style as in datasheet. YT is marking where Y is tempco and T is tolerance (0.01%), but that datasheet doesnt have any info on "Y" tempco code..

author: Andreas
author_rank: Super Contributor
timestamp: March 27, 2024, 07:51:48 pm
content: Hello,Y usually stands for +/-2.5 ppm/Ksee for example FLCY resistors from ALPHAwith best regardsAndreas