Precision resistors + rant about strange values - Page 1
Forum section: electronics / general

author: DC1MC
author_rank: Super Contributor
timestamp: December 15, 2018, 09:24:07 pm
content: Hello everybody, for the previously discussed projects I've bought a bag of precision resistors from this seller:https://www.ebay.de/itm/100-St-Widerstand-Präzisions-Dale-RN70C-u-ä-NOS-Neuware/332047608889I thought that they look nice and maybe I'll find something useful, well the resistors arrived, they are really more than in the picture and of more sorts (pictures of the actual stuff at request), but the, except for 1(one) 10.001KOHM and a couple of 200K and 250K, all the rest were the most strange values ever, who actually needs 10001Ohm, and this is the good case, but I have something like 4321Ohm, 178.000KOhm, a gadzillion of 16200Ohm and so on...Who the hell needs these values, are there some "magic values" used in precision circuits that I don't know off and all these weird values guys are actually useful ?!?!?/endOn the other hand the HP 3456A that just arrived seem to be OK and the calibration seem to still hold, in the miserable improvised setup it measures like in the attached pictureSorry for the rant and cheers,DC1MC

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 15, 2018, 09:43:40 pm
content: Nothing at all weird about 16.2 kohms. It's common for weird values to combine with other weird values to give useful ratios. Why do you think 9.09 values are so common? I bought some old wire wound parts, and one bag is 333.333 ohms. Not at all standard, but I can see lots of ways it would be useful.

author: james_s
author_rank: Super Contributor
timestamp: December 15, 2018, 10:33:56 pm
content: I've found that a lot of times random grab bags of parts contain a lot of oddball stuff, I suppose if they were more standard sought after parts they'd be sorted and sold as what they are.

author: dzseki
author_rank: Frequent Contributor
timestamp: December 15, 2018, 10:42:32 pm
content: I have been wondering on the same thing a while ago checking a box of 109930pF 0.25% capacitors

author: GregDunn
author_rank: Frequent Contributor
timestamp: December 15, 2018, 11:03:49 pm
content: My bet is that they had several large orders of precision parts for some buyer, and these are the leftovers. You never know what people are going to spec for custom projects, or how many you'll have remaining when they end the manufacturing run...

author: tggzzz
author_rank: Super Contributor
timestamp: December 16, 2018, 01:26:18 am
content: I have piece of test equipment (Tektronix 115) that has a 908pF 400V cap, tolerance not specified in the parts list. There are also 0.0085uF, 0.00488uF, 0.00495uF caps.https://www.flickr.com/photos/anachrocomputer/40065802790/in/album-72157690644170820/

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 16, 2018, 04:13:57 am
content: Aw, come on...those values look quite practical and straightforward.I just took a look to my precision resistor stocks, and found:26.769k 0.01%378.940k 0.1%293.94k 0.1%315.62k 0.05%No idea where they came from.10.001k is a rather good 10k resistor, I think.

author: tggzzz
author_rank: Super Contributor
timestamp: December 16, 2018, 09:43:43 am
content: SighLooking at my Solartron 7075, the parts list specifies amongst others: 100.84, 1176.6, 114.35k, 2.436l, 4.844k, 9.624k, 19.124k, 699.5k, 1.178k, 69.96k, 44.2, 8.208k, 910.6k, 8.19M, 10.96k, 6.96k.Now there are some obvious harmonic relationships in there, the precision varies from 0.1% to 0.005%, but the temperature coefficient is more important.

author: DC1MC
author_rank: Super Contributor
timestamp: December 16, 2018, 05:19:04 pm
content: Hello again, after sorting to my grab bag I've got some useful values and starting to understand how they fit together, also some of those resistors are scarringly accurate, even being 1 or .1% tolerance.Also they are pretty much imune to light temperature variations and very stable generally.Now I have a couple of questions, maybe some one who has a good experience/knowledge of Dale/IRC corporation may help me (and others):All of the resistors are marked with a RNxx (xx = numeric value) or RNxxT (T = letter) or RNCxx, For example RN60C, RN70B, RWR89S (singleton),RN70D and so on.Most of the values are of type: (n)nnneX, that is 3 or 4 value coefficient, exponent and a letter, for example: 1004F, 2000FR and so on ?- What signifies these notations (precision, tempco, other) ?- Another question, if there are some volt-nuts proletarians wannabes in Germany, that are interested in these resistors (not everybody can afford vacuum sealed Vishays carefully aged by pure virgin hands) should we get some bags each and organize a swap, for example I have some 301K 1% and some 18,200K along with a lot of 19,60K, 1,96K and 196ohm pieces that I want to match, that is, have them as close as possible in value ?If anybody is interested, please PM me, I'll make an Excel sheet with what I have and maybe we can swap.Cheers,DC1MC

author: ap
author_rank: Frequent Contributor
timestamp: December 16, 2018, 05:47:11 pm
content: RN, RNC... are military designators for resistors. See MIL specs or general datasheets.

author: DC1MC
author_rank: Super Contributor
timestamp: December 16, 2018, 06:01:37 pm
content: Quote from: Neomys Sapiens on December 16, 2018, 04:13:57 amTrue, but it was the one somehow sane value that I've found at the time, after carefully going trough them I've got an 1M, 2 x 200Ohm, 2x200KOhmx, 4x250KOhm, so it's not that bad.Now if I'll find some exchange partners to get a bunch of them close, it will be even better.I also was very happy that finally I've got some positive tempco guys, all my other (somehow) precision resistors were negative tepco.Cheers,DC1MC

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 16, 2018, 11:29:56 pm
content: As regards my stock, I think you must have the inventory. Go resistors, select for 'PrecRes' in Col.A and the look at the amount.

author: ArthurDent
author_rank: Super Contributor
timestamp: December 25, 2018, 12:54:25 am
content: Years ago I bought a huge analog computer that had precision resistors on many of the plug-in boards as well as 1600+ vacuum tubes. I ended up with a LOT of .005% ww resistors, many were common values like 1M, 100K, 50K, etc.. A lot more were not so common values but I found that I could use some of those to get values I needed for dividers, etc.. Even though they were made 60 years ago they are still within tolerance.

author: DC1MC
author_rank: Super Contributor
timestamp: December 25, 2018, 09:42:34 am
content: Quote from: Krytron on December 25, 2018, 03:55:06 amVery interesting, now I know what I have, thanks a lotCheers,DC1MC