How to order from Vishay Foil resistors? - Page 1
Forum section: electronics / general

author: nour
author_rank: Frequent Contributor
timestamp: May 28, 2017, 11:24:42 pm
content: I want to order some foil resistors from Vishay and when I visited their websitehttp://www.vishaypg.com/foil-resistors/I couldn't find add to cart or buy button!I am not used to buy from them I don't know the process!They have 6 ways to get parts from them in "How to buy page", which I am really not sure which one to use because I am an international buyer and may have one try to do this and also I just want to buy limited amount not too much.Also are their prices any different from the distributors?And how much time they take to send the items?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 28, 2017, 11:35:55 pm
content: The button marked "how to order" might be a good starting point....http://www.vishaypg.com/foil-resistors/how-to-order/

author: nour
author_rank: Frequent Contributor
timestamp: May 28, 2017, 11:38:31 pm
content: Thats a lot of reading and honestly I have tried to go through it and I was lost

author: mdszy
author_rank: Unknown
timestamp: May 29, 2017, 03:17:17 am
content: Quote from: nour on May 28, 2017, 11:38:31 pmIf the "how to order" page from a manufacturer is "a lot of reading" for you, then maybe you're not someone they want as a customer...

author: nour
author_rank: Frequent Contributor
timestamp: May 29, 2017, 06:56:14 am
content: What kind of thinking is that?? They have listed 6 different ways to order from them and the stuff I want to order is expensive and I may have only one try to do it because I am an international buyer and I am only building some prototypes.If you don't have a proper answer why bother writing a useless oneI am used to buy using the simple way, just add to cart and pay and later receive my order just like Digikey, Mouser, Tme , Amazon, eBay and moreThey don't have such a click and order thing, they require a different methodology which I am not aware of, so what's the problem If I asked someone? in a forum about it and seek others experience in this situation??

author: tszaboo
author_rank: Super Contributor
timestamp: May 29, 2017, 07:29:08 am
content: If you dont like it, you are free to take your business elsewhere. Good luck with that, finding replacement for a VPG resistor.Quote from: nour on May 29, 2017, 06:56:14 amIts a problem, only because it is on their website.

author: nour
author_rank: Frequent Contributor
timestamp: May 29, 2017, 07:39:34 am
content: Quote from: NANDBlog on May 29, 2017, 07:29:08 amSo basically that's what you have understood from my last phraseSo If I don't like it and I should go somewhere else with my business, why bother opening this thread and write those replies and wasting my timeI don't understand, what is the point of wasting time if you don't know how to answer a question asked by someone in a forum?

author: TiN
author_rank: Super Contributor
timestamp: May 29, 2017, 07:54:13 am
content: There is email in datasheets to order, and contact info on VPG site, which is available to order.That's how I ordered VPG parts some years ago. Give them a call and they will tell you how to buy VPGs.And if you think you very valuable customer to them with few resistors for 100$, that's very wishful thinking.If you want easy order one-button click - go digikey,mouser or ebay and don't compain.Many of VPG resistors are ordered and manufactured per order, as you may want to have custom non-standard resistance values, tempco matching, PMO aging or packaging variants to meet specs you want, so they cannot list every possible option in simple buy-it-now cart without making it confusing. Pricing also vary a LOT

author: nour
author_rank: Frequent Contributor
timestamp: May 29, 2017, 08:01:56 am
content: Quote from: TiN on May 29, 2017, 07:54:13 amThank you very much, I was somehow waiting for you to reply because I read somewhere that you have ordered from them when you was working on your KX project.Anyway, The main reason why I am asking a part of the ambiguity in the process, that I want to know if I can save any money if I bought from them directly instead of buying from a distributor, also Digikey is out of there Foil resistors(almost) and it will take around 10 weeks to arrive at them!

author: TiN
author_rank: Super Contributor
timestamp: May 29, 2017, 08:04:40 am
content: Saving money and buying precision parts are not compatible terms. I've waited 22 weeks with my direct order (standard resistors leadtime was 6 weeks, but I've had few resistors with custom spec and tempco matching, which needed 20 weeks lead time). If you want fast and quick, go for ebay or in-stock at Digikey/etc.

author: nour
author_rank: Frequent Contributor
timestamp: May 29, 2017, 08:19:41 am
content: Quote from: TiN on May 29, 2017, 08:04:40 amYes, I totally agree with you, but I am not talking about this kind of saving because I am still going to buy the same part whether from a distributor or from the manufacturer, the point is that I want to just find the cheapest among them all!

author: tszaboo
author_rank: Super Contributor
timestamp: May 29, 2017, 08:23:52 am
content: You have no idea how this industry works, do you?

author: mdszy
author_rank: Unknown
timestamp: May 29, 2017, 02:11:40 pm
content: Quote from: nour on May 29, 2017, 08:19:41 amHow much are you even looking to buy from Vishay? Given how you've been handling this, I wouldn't be surprised if you didn't even come anywhere near an MOQ... Plus, like another person said, spending $100 on a few resistors doesn't make you a valued customer, and from the sounds of it, some poor salesperson would probably have to be holding your hand through this whole process.

author: MK
author_rank: Regular Contributor
timestamp: May 29, 2017, 05:38:01 pm
content: The other thing to consider is that although *some* meet an absolutely amazing typical spec, it does seem anecdotaly that many more parts are nearer to the maximum limits provided on their specs, so in order to be sure you need to be able to order spares and also to have the capability of measuring the drift and TC so that lesser spec samples may be used in less critical circuits.

author: nour
author_rank: Frequent Contributor
timestamp: May 29, 2017, 06:54:08 pm
content: Quote from: mdszy on May 29, 2017, 02:11:40 pmAlmost 500-1000$, haven't yet figured out the exact list.100$ may only buy me 1or 2 VFR!

author: cellularmitosis
author_rank: Unknown
timestamp: May 30, 2017, 12:15:22 am
content: Nour is taking a lot of heat in this thread, so I'll throw this out there:I requested a quote from them (using their website) about a month ago and never heard back from them. I just assumed they don't even deal in quantities of 5 or 6 resistors at all (to the point where they don't even bother replying to say "go away"). Maybe I was just unlucky? Or am I just completely beneath their radar?(I only found out about the various distributors today, like Texas Components, so I'll probably go through them in the future either way).

author: e61_phil
author_rank: Frequent Contributor
timestamp: May 30, 2017, 12:35:50 am
content: Quote from: cellularmitosis on May 30, 2017, 12:15:22 amI had no problem in buying only 5 or 6 resistors as a private person from them. I ordered my resistors via Powertron in germany (official distributor for my region).

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: May 30, 2017, 01:01:13 am
content: Why are you considering such expensive resistors, they won't get you any significant improvement over good PWW resistors (which are the recommended resistor for LTZ circuits) and they cost a lot less!

author: ebclr
author_rank: Super Contributor
timestamp: May 30, 2017, 01:06:55 am
content: VishayFoilResistors? @VPGFoil Jan 25MoreNo MOQ, any value, fast quotes, fast delivery, #ultra_high_precision resistors via –http://www.resistors4u.comexpress hub.

author: cellularmitosis
author_rank: Unknown
timestamp: May 30, 2017, 01:31:44 am
content: Edwin, you are correct! At the time, I didn't know how expensive they were, and wanted to find out.

author: nour
author_rank: Frequent Contributor
timestamp: May 30, 2017, 07:34:51 am
content: Quote from: cellularmitosis on May 30, 2017, 12:15:22 amWell, some heat will make me more stablelike LM399

author: nour
author_rank: Frequent Contributor
timestamp: May 30, 2017, 07:49:54 am
content: Quote from: Edwin G. Pettis on May 30, 2017, 01:01:13 amI am sorry, I am still a beginner in this metrology world, to be specific I don't know much, I just have seen a lot of folks doing this and using those high precision foil resistors and I have seen some teardown for some precision instruments doing the same so I thought that would be the way to go!Anyway, I will consider your advice but first I need to know what is PWW resistors?do you mean precision wirewound resistors, right? if so, the most stable one I have found on Digikey was 10 pmm\c so would that be good enough for LTZ1000A ref or even for LM399AH? is there a better(stable) than those on Digikey?

author: 0.01C
author_rank: Regular Contributor
timestamp: May 30, 2017, 01:03:29 pm
content: Quote from: nour on May 28, 2017, 11:24:42 pmWe order 100R and 9.998k from China Vishay agent at $20-30/pc.

author: nour
author_rank: Frequent Contributor
timestamp: May 30, 2017, 03:23:25 pm
content: Quote from: 0.01C on May 30, 2017, 01:03:29 pmCan we do communication by English with them? is it easy to order from them, how much time it takes to get standard values?

author: cellularmitosis
author_rank: Unknown
timestamp: May 30, 2017, 05:22:24 pm
content: Nour, my understanding is that though foils may have a better tempco, precision wirewound will have better long term drift. Tempco can be compensated for, but the only solution for long term drift is calibration -- pick your poison. My plan is to (eventually) try both and compare

author: nour
author_rank: Frequent Contributor
timestamp: May 30, 2017, 06:21:28 pm
content: Quote from: cellularmitosis on May 30, 2017, 05:22:24 pmI actually don't know much about what you have mentioned to confirm it or not and also as you said I will try both.But if wirewound is good enough, how much enough should be enough?, for example, is it good enough for LM399 or LTZ1000. if so I would go for it!Originally I want two sets, one as a lab standard(1,10K) and the other set for building voltage reference standard!

author: e61_phil
author_rank: Frequent Contributor
timestamp: May 30, 2017, 06:24:30 pm
content: Which resistors do you mean at the LM399? The divider to achieve 10V is critical. Alle other resistors (including LTZ1000) are less critical in terms of TC.

author: nour
author_rank: Frequent Contributor
timestamp: May 30, 2017, 06:41:42 pm
content: Quote from: e61_phil on May 30, 2017, 06:24:30 pmI mean the one to achieve the 10V, the 9K and the 20KAnd I will add another stage with voltage divider and a buffer to get 5 or 4.096V

author: kj7e
author_rank: Frequent Contributor
timestamp: May 30, 2017, 07:10:41 pm
content: I'm in the same boat, KX LTZ1000 boards ordered, all other parts from Digikey ordered, stuck trying to get the VPG parts. I did speak with a VPG rep, who CC'ed me to a local sales rep atwww.uhpresistors.com, but they have yet to respond, even to my follow up.Edit, they just responded with a quote and 15 week estimate lead time.

author: e61_phil
author_rank: Frequent Contributor
timestamp: May 30, 2017, 08:21:46 pm
content: Quote from: nour on May 30, 2017, 06:41:42 pmThere is nothing special involved. The gain is simply 1+R1/R2. Therefore you can calculate the total derivative and see the impact of the resistors.

author: e61_phil
author_rank: Frequent Contributor
timestamp: May 30, 2017, 08:40:08 pm
content: ..or if you are a lazy boy (like me). You could just "simulate" the error, like so:Code:tc = np.linspace(-5e-6, 5e-6, 1000)R1 = 9.1R2 = 20exact = 1+R1/R2ratio_err = []for tc1 in tc:for tc2 in tc:ratio = 1+( R1*(1+tc1) )/( R2*(1+tc2) )ratio_err.append( (ratio-exact)/exact*1e6 )In this example the resistors have both +/-5ppm