Is wirewound resistors stabile? - Page 1
Forum section: electronics / general

author: 001
author_rank: Super Contributor
timestamp: November 09, 2017, 02:00:27 pm
content: Is wirewound resistors "stabile" with temperature coefficient about 160ppm?It means that deviation is 0.16% per every 10 celsius, isn`t it?But wirewound resistors tolerance often marked as 0.1-0.25%Why temperature deviation more than marked tolerance?

author: Vgkid
author_rank: Super Contributor
timestamp: November 09, 2017, 03:34:29 pm
content: Wirewound resistors are generally stable , but at 160ppm/c those would be power resistors. In that usage stability is not important. If at 0.10% , I feel there could be a temperature coefficient miswriting on the datasheet(or that error is available at a certain range , with a lower tc).

author: schmitt trigger
author_rank: Super Contributor
timestamp: November 09, 2017, 04:07:24 pm
content: The wire in a wirewound resistor could be made of different materials; optimized for its intended application.I would think that the common power resistor's wire is optimized for high temperature and surge capability.I'm pretty sure some volt-nuts in this forum can provide further details, but there are certain wire materials which can be optimized for stability and low tempco.

author: MK
author_rank: Regular Contributor
timestamp: November 09, 2017, 04:24:59 pm
content: The chances are that it is manganin, stable if not overheated, but also used as a pressure sensor in nulear tests etc. Some wirewound resistors have a tempco that is very low, it depends upon the intended use and expected temperature range of the equipment it is intended for.I once had to deny a calibration sticker for a PAT tester as the tempco of the sense resistor that it dropped out of spec during any test run...So in that use the power resistor should have either had a bigger heatsink or been specified for a lower tempco, from memory it was a 50W aluminium clad wirewound with no heatsink.At the other end you have the SR1 and other standard resistors with >1ppm tempco typically.

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: November 10, 2017, 06:26:28 pm
content: No, Manganin is not used for power resistors, its TCR becomes unstable above about 60°C. Several alloys are used for power resistors, Cupron is the main one with several other alloys such as #60,#90 and #180, all having a fairly high operating temperature as power resistors can have hot spots of up to 350°C, their overall TCRs are usually over 100 PPM/°C. Relative new comers, so-called precision powers, mostly under 5 watts rating and 1% tolerance, have lower TCRs because they are made with Evanohm and have limited operating temperatures, these are under 100 PPM/°C TCRs. The standard power resistor made with lugs strapped around the ends of the ceramic core have inherent high TCRs.Precision wire wound resistors are an entirely different animal and have little in common with power resistors except that both have wire wound onto a bobbin with leads. Precision can have the lowest TCRs of most precision resistors and have the lowest inherent thermal noise if made correctly. Precisions can be made with power ratings of 2 watts or higher but are not considered power resistors.

author: 001
author_rank: Super Contributor
timestamp: November 10, 2017, 07:33:29 pm
content: Noit is NOT power resistorsit is 0.5/1W bifillar wirewound for antique metershttp://www.quartz1.com/price/PIC/480Q0712500.pdf

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: November 10, 2017, 11:52:25 pm
content: According to the Russian data sheet you linked to, it cannot be Manganin as the operating temperature is up to +125°C, if I'm reading it right, the TCR specified is ±100 PPM to ±150 PPM/°C so this resistor is using something similar to Cupron for the alloy and this would be classed as a low power power resistor not a precision. Given the tolerances, I would class it as a semi-precision power resistor but it definitely not a precision wire wound such as I make.

author: Mickle T.
author_rank: Frequent Contributor
timestamp: November 11, 2017, 11:47:02 am
content: PTMN - one of the first inexpensive PWW resistors, produced after the WW2: P - wirewound, T - precision, M - compact, N - NiCr (or M - Manganin).Now they are completely replaced with a hermetically sealed PWW, e.g. R2-100 with guaranteed 0.2 ppm/C and 5 ppm tolerance.

author: 001
author_rank: Super Contributor
timestamp: November 11, 2017, 02:26:39 pm
content: Sanx!And what about its stability?

author: Mickle T.
author_rank: Frequent Contributor
timestamp: November 11, 2017, 08:02:45 pm
content: PTMN isn't a metrological grade resistors. It have a bad long-term stability about 100-200 ppm/year.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 11, 2017, 10:45:42 pm
content: Quote from: 001 on November 09, 2017, 02:00:27 pmTolerance & stability are two different things.It's value may be within 0.1- 0.25% of the marked value at a specified temperature, but it may change by more than that as temperature varies.As a lad, working at an Electronic parts reseller, I wondered why we sold 5% "high stability"resistors.A more senior staff member pointed out that the two things were not incompatible, as the resistor may be a bit "off value", but it will stay at close to that value over time & temperature change.

author: 001
author_rank: Super Contributor
timestamp: November 11, 2017, 10:59:35 pm
content: Awesome answersI'm gonna use this 40-50 years old resistors. Is it good idea if my affordable deviation per year about 0,1%? I check all units. Acuracy is ok after 40-50 shelf storage

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 11, 2017, 11:06:51 pm
content: General statements such as not suitable for metrology are meaningless.The resistors have a stated performance. That stated performance may or may not meet the needs of the application. The actual performance after 50 years may or may not meet the users needs although I believe it is likely that temperature stability will be similar to original specification.Only the user can determine this suitability. If calibration of a 5 digit meter is the objective they are clearly not suitable, but for a 3 digit performance in a circuit or calibration use they may be fine.

author: chuckb
author_rank: Frequent Contributor
timestamp: November 12, 2017, 12:15:05 pm
content: Quote from: Mickle T. on November 11, 2017, 11:47:02 amMickle T.Who makes these R2-100 resistors?

author: TiN
author_rank: Super Contributor
timestamp: November 12, 2017, 01:27:52 pm
content: chuckbThey are made byNIIEMP, which stands from JSC Penza Scientific Research Institute of Electron-Mechanical Devices.

author: HalFET
author_rank: Frequent Contributor
timestamp: November 12, 2017, 03:44:53 pm
content: I've always been worried more about them picking up external magnetic fields due to their coil like behaviour, not quite sure if that's silly or not.

author: 001
author_rank: Super Contributor
timestamp: November 13, 2017, 10:24:01 am
content: Since coils bifillar magnetics fields is not a problem

author: chuckb
author_rank: Frequent Contributor
timestamp: November 13, 2017, 04:39:37 pm
content: Quote from: TiN on November 12, 2017, 01:27:52 pmIs there a source of supply for these resistors outside of Russia?

author: schmitt trigger
author_rank: Super Contributor
timestamp: November 14, 2017, 01:38:43 pm
content: Or perhaps they are listed on Ebay?I've purchased Nixies and Dekatrons from vendors in Russia, which were listed on Ebay.Other than the long shipment time, the prices were good and the quality excellent.

author: 001
author_rank: Super Contributor
timestamp: November 14, 2017, 03:37:27 pm
content: Nixies is not russian parts but oldsovietNOSNew russian parts are not cheap since no reason to make consumer electronics in Russia. Military & aerospace only.I called them today. No samplesDo You need bulk of resistors?

author: AG7CK
author_rank: Regular Contributor
timestamp: November 15, 2017, 04:20:58 am
content: I have one precision resistor type S5-60 (2k, +- 0.005%, tempco 3ppm/deg) from NIIEMP. The eBay seller said it was from 1990.However - when looking around a bit, it seems that they are still in production:http://niiemp.ru/produktsiya-i-uslugi/provolochnye-metallofolgovye-kermetnye-rezistory-i-nr/provolochnye/item/c5-60.htmlWhen translating from website via machine translator:https://translate.googleusercontent.com/translate_c?depth=1&hl=en&ie=UTF8&prev=_t&rurl=translate.google.com&sl=auto&sp=nmt4&tl=en&u=http://niiemp.ru/produktsiya-i-uslugi/provolochnye-metallofolgovye-kermetnye-rezistory-i-nr/provolochnye/item/c5-60.html&usg=ALkJrhiIgvjq4qeQoY9fOUlaWj_EOB0B_git says "super precision ... highly stable ... metrological ... "Someone from Russia should open a thread for a group buy just as for the Chinese Zeners.Here is the (last century) datasheet I got from the seller:http://www.155la3.ru/datafiles/s5_60_tu_1983.pdf

author: TiN
author_rank: Super Contributor
timestamp: November 15, 2017, 04:24:59 am
content: VPG VHP likely to be cheaper

author: chuckb
author_rank: Frequent Contributor
timestamp: November 15, 2017, 03:06:22 pm
content: The VHP203 is a great part. I recently bought several 80K ohm parts. After testing and characterization I intend to parallel two of them to make a "minimum temp co" 40K ohm statistical reference for my 3458A. This is on my project list...Even the great VHP203 (Z-Foil) is specified at 2 ppm / deg C (MAX). There are typical values much lower than that but unless it's for home use or I screen the parts on a production basis, the typical values are of no use to me.Does anyone know if the Vishay PMO process guarantees a maximum temp co?The notes for the R2-100 specified a guaranteed 0.2 ppm / deg C. That spec is what caught my attention. That is the kind of specification I look for with parts I use in production. I'm sure they will be custom built, expensive, and have a long lead time but it will save manufacturing time and expense later. If I can get them.