Are there any manufacturers of precision resistors other than Vishay ?

[deepfryed]

I was browsing for some precision resistors during my lunch break, as one does   and realised that there's not a lot of choices when it comes to precision resistors other than Vishay. Are they a resistor monopoly ? Just curious.

[Kim Christensen]

Seems to be a few in both SMD and thru-hole at DigiKey:

[deepfryed]

sorry I should've said 0.005% or better

[SeanB]

Small low volume market, and they bought up all the competition a long time ago, and thus pretty much have a near monopoly on that market, aside from some really niche manufacturers who can do things they cannot do. But in this market volumes are really low, and prices are very high, and not at all profitable.

[Smokey]

https://riedon.com/

[deepfryed]

I didn't know about them, looks like Bourns own them. I can't find their 0.005% resistors on digikey though I can see the 0.01% ones

https://www.digikey.com.au/en/products/detail/riedon/USR2G-1KX2/1650022

Thanks for the info.

[jbb]

Rohm (to some extent) and, for those who are brave-of-wallet, https://www.isabellenhuette.de/en/

[deepfryed]

Rohm (to some extent) and, for those who are brave-of-wallet, https://www.isabellenhuette.de/en/

If it's "ask us for a quote" then it's too expensive for me 

[Smokey]

...looks like Bourns own them. ...

https://www.bourns.com/news/press-releases/pr/2023/04/17/bourns-acquires-riedon-inc.-a-leading-manufacturer-of-resistors

Interesting.  Looks like that just happened.

[jbb]

If it's "ask us for a quote" then it's too expensive for me 

So true.

The thought occurs: there are probably some really excellent parts from Chinese manufacturers (if nothing else, for strategic reasons), but I don’t know how to find them.

[ch_scr]

If it's "ask us for a quote" then it's too expensive for me 

So true.

The thought occurs: there are probably some really excellent parts from Chinese manufacturers (if nothing else, for strategic reasons), but I don’t know how to find them.

Maybe I found one, even if they are just shy of the precision requirement from the original request: Token / DeMint

[r6502]

sorry I should've said 0.005% or better

If you talk about resistors with this uncertainty of it's value I think, you should also specify the TC and the needed value and power. What is your application? Without this information it is difficult to recommend a company, as many of  them are specialised for niche products.

The smaller the uncertainty, the lower the TC, the higher the price ...

Guido

[deepfryed]

If you talk about resistors with this uncertainty of it's value I think, you should also specify the TC and the needed value and power. What is your application?

Thinking of building a precision reference / decade box. TCR +/-0.2ppm/C and 50ppm tolerance and it's looking like it's going to be an expensive exercise :

 

[bdunham7]

TCR +/-0.2ppm/C and 50ppm tolerance

You might want to read and discuss that spec sheet a bit more.

[deepfryed]

You might want to read and discuss that spec sheet a bit more.

I'm sure there's plenty of unknowns for me as a novice. I am trying to put together something with best tolerance / temp co to use as a reference, there's wattage considerations but beyond that not sure what I need to be looking for. I guess if I can characterise the components with a known standard / reference for a longer period of time then I can use cheaper resistors, but that's going to cost me a fair bit of change here.

[alm]

I'm sure there's plenty of unknowns for me as a novice. I am trying to put together something with best tolerance / temp co to use as a reference, there's wattage considerations but beyond that not sure what I need to be looking for. I guess if I can characterise the components with a known standard / reference for a longer period of time then I can use cheaper resistors, but that's going to cost me a fair bit of change here.

What bdunham7 is getting at is that the Vishay Precision Group is quite good at playing specmanship, presenting specifications in such a way that they make the part look better than it is. I'm not saying they are not good resistors. But I'd ignore any "typical" figure in the data sheet. For example, a typical TC of 0.2 +/ 2 ppm/K, I would look at the 2 ppm/K figure and not at the bold 0.05 ppm/K figure at the top of the data sheet that might be available if you pay top dollar for selected resistors. I would also not count on this "typical" parabolic curve they claim for Z-foil. See TiN's website for a wealth of data on this, and on this forum especially Andreas posted a lot of data in T.C. measurements on precision resistors. Also note this this post by Dr. Frank on this subject.

So take VPG datasheets with a bucket of salt, especially regarding temperature coefficient.

Also, I wouldn't focus so much on initial accuracy. For precision applications usually the most important is stability over time, temperature, humidity, load, etc. You can improve the initial accuracy by measuring them or paying someone (e.g. the manufacturer) to do that. Being extremely close to the nominal value rarely matters for a standard. But you can't do much about stability over time. And you can't improve the temperature stability except by either stabilizing the temperature or trying to find resistors with an opposite temperature coefficient to correct the tempco. See how the Fluke 742A uses this to achieve a low tempco. What good is 50 ppm initial accuracy if within a year it drifted 100 ppm?

The T.C. measurements on precision resistors might also give you an idea of other resistor brands, but don't expect < 1 ppm/K tempcos (from VPG or any other) or 50 ppm tolerance (which shouldn't be a priority at all as I just described). If you want < 1 ppm/K, prepare to have to buy a bunch of resistors and test them yourself. Some examples are TE UPW 25/50 resistors, General Resistance Econistors (sold by Rhopoint) and Edwin Pettis (Ultrohm). He is sometimes active on this forum used to make individual resistors to order for very reasonable prices, but I don't know how active he still is and what delivery times are like.

But Vishay has certainly been quite successful in gobbling up competitors.

[deepfryed]

Thanks, that was super useful and a lot of reading for me to get through. Much appreciated!

[TimFox]

Not directly related to the original question, an historical point:
I find interesting the extent to which Vishay Intertechnology has grown since it spun off Vishay Precision Group (the manufacturer of precision metal-foil parts).
To a large extent, it has re-united the divisions spun off by Sprague, plus picking up other "normal" resistor companies (e.g., Dale).

[Tomorokoshi]

https://riedon.com/

I was going to suggest that. I hope Bourns doesn't trash it for rightsizing or synergistic reasons.

[timeandfrequency]

[...]
But Vishay has certainly been quite successful in gobbling up competitors.

Hi alm,
You coudn't say better.
Example with the manufacturer 'SFER', better known as 'Sfernice' (Société Française de l'Electro Résistance de Nice), France, that was bought by Vishay in 1988.
Digikey and Mouser currently sell their products branded as 'Vishay/Sfernice'.

A 2 min video about 'SFER' (in French) :

[Electrole]

The other day, when looking for alternatives for VPG resistors, I found this German company:
https://www.megatron.de/kategorie/praezisions-widerstaende.html
Do any of you have any experience with the company and their resistors?

[tszaboo]

Rohm (to some extent) and, for those who are brave-of-wallet, https://www.isabellenhuette.de/en/

If it's "ask us for a quote" then it's too expensive for me 

They are a lot cheaper than Vishay PG resistors for high precision current shunts.

What bdunham7 is getting at is that the Vishay Precision Group is quite good at playing specmanship, presenting specifications in such a way that they make the part look better than it is. I'm not saying they are not good resistors. But I'd ignore any "typical" figure in the data sheet.

Yeah if in the desert it's 40 degrees during the day, -20 during the night, then the typical temperature is 20 degrees, quite comfortable. That's the typical value.

If you talk about resistors with this uncertainty of it's value I think, you should also specify the TC and the needed value and power. What is your application?

Thinking of building a precision reference / decade box. TCR +/-0.2ppm/C and 50ppm tolerance and it's looking like it's going to be an expensive exercise :

 

Instead of trying to buy individual resistors, try to get some NOS manganin wire on ebay, that will be a lot cheaper.

[alm]

The other day, when looking for alternatives for VPG resistors, I found this German company:
https://www.megatron.de/kategorie/praezisions-widerstaende.html
Do any of you have any experience with the company and their resistors?

No experience, but from packaging style, datasheet and the pictures without any printing it looks like a VHP reseller to me.

Thinking of building a precision reference / decade box. TCR +/-0.2ppm/C and 50ppm tolerance and it's looking like it's going to be an expensive exercise :

 

Instead of trying to buy individual resistors, try to get some NOS manganin wire on ebay, that will be a lot cheaper.

Good luck getting a 0.2 ppm/C tempco with Manganin! Reading the early 20th century NBS papers on the Rosa and Thomas type resistors might be instructive, but the solution for tempco back then was put them in a temperature stabilized oil bath. This is still a valid strategy, like the Fluke SL935 prototype.

[tridac]

Perhaps look at it a different way, as in why the need for 0.005% ?, lab standard territory. There are quite a few manufacturers of metal film with low tempco and aging, standard values, which are much cheaper, Buy those in quantity, then  select from those. Balance cost of test time against cost of high spec parts.  Perhaps modify the circuit to enable use of a lower spec parts, software calibration. In one of their resistance calibrators, the 5450, Fluke use close tolerance ww in oil, then calibrate with a display to show *actual* measured values, which I thought a pretty cool idea...

[alligatorblues]

If you talk about resistors with this uncertainty of it's value I think, you should also specify the TC and the needed value and power. What is your application?

Thinking of building a precision reference / decade box. TCR +/-0.2ppm/C and 50ppm tolerance and it's looking like it's going to be an expensive exercise :

 

You won't be able to do a one off for less than you can purchase the equivalent complete. For one thing, the wire for the resistors comes in spools of 10 miles or more. Then it has to be heat treated to make it more stable. After that you have to wind them in specific patterns to avoid induction.

And you cant stretch the wire at all, or it becomes very unstable. And you need to make about 40 of those. Making a decade box is a loser project. If you want to use thick-film laser-trimmed resistors, like Vishay's precision resistors, those cost $50-$100 ea. And you have to wait for 10 months for delivery.

However, a much more doable project is to make a highly stable resistance standard. You have to read a lot first, because there's a lot to know about the different ways to do it. NIST has some excellent publications on how to make primary resistance transfer standards.

You'll also need to learn the mathematics and engineering involved with working with high-resistance wire, and familiarize yourself with the different types. I made a 1 Ohm standard that was accurate to +-10ppm. I sold that one to a guy who was calibrating a Fluke multipurpose calibrator.

He already had the other artifacts. One thing is for certain. Metrology is not a good way to make money.

[laichh]

The other day, when looking for alternatives for VPG resistors, I found this German company:
https://www.megatron.de/kategorie/praezisions-widerstaende.html
Do any of you have any experience with the company and their resistors?

Tried, they are re-badged AE resistor.