Poor Man's product idea for LT/AD - Page 1
Forum section: electronics / general

author: zhtoor
author_rank: Frequent Contributor
timestamp: December 23, 2017, 07:54:25 am
content: Hello,here is a product idea for Linear Technology / Analog Devices.they already have a product called LT5400 which is a set of 4 closely matched resistor with excellent thermal tracking.now if they could only come with the following products also:-1. LT5406 - a set of 6 closely matched -> for all integral ratios like 1/10, 2/10 ... 9/102. LT5412 - a set of 12 closely matched -> kvd's, hammon's etc.what does the community say about this?regards.-zia

author: HalFET
author_rank: Frequent Contributor
timestamp: December 23, 2017, 08:15:12 am
content: That they're unlikely to venture into Caddock's thick film co-fired hybrid market. For it to be worth it for them they'd need a very large customer to ask it.

author: ramon
author_rank: Regular Contributor
timestamp: December 23, 2017, 11:17:43 am
content: Zhtoor, I think what you want already exists. It is called UPRNS (UPRN-S, or UPRN-SIL).The lowest TCR available is ±5% PPM (C7). And tolerance as low as ±0.02% (A2).Sold by several manufacturers (or resellers?) in China (Anhui, Shenzhen) and Taiwan. No idea which one is the true manufacturer.I was also thinking about a 12 resistors network for some kind of KVD. And I got a quote for a 10K resistor network with 13 pins (UPRNS-13-Type1-10K-A2, according to token.com.tw datasheet). Each resistor network is priced at $28 (not included shipping cost). Price is not too bad for a dozen of precision resistors if those actually meet the specs.I can handle a group buy if there are at least 15 persons interested.As there are many others in this forum from China, does anyone has more information about which one is the true manufacturer? or even have quotes from them? I will be happy to join any other group buy if price is cheaper for the highest TCR and tolerance specs (C7/A2).Websites:http://www.token.com.tw/resistor-ppm/uprns-resistor.htmhttp://www.ebg.com.cn/a/chanpinzhongxin/jingmijinshumodianzuqi/20130529/UPRNS.htmlhttp://www.thunder-resistor.com/product_view_44_128.htmlhttp://www.bds.com.cn/en.php/Cate/index/pid/9/id/32http://www.doublecircle.com/en/product.php?page=4PDF specs:http://www.token.com.tw/pdf/resistor-ppm/precision-network-resistor-uprns.pdfhttp://www.ebg.com.cn/en/uploads/soft/130719/UPRNS.pdfhttp://www.thunder-resistor.com/uFile/1906/20091230174355174.pdfhttp://www.bds.com.cn/Public/data/file/201312/UPRN(S).pdfhttp://www.doublecircle.com/doc_down/201212130957199658.pdf

author: zhtoor
author_rank: Frequent Contributor
timestamp: December 23, 2017, 11:32:41 am
content: thanks. i got a quote from token.com.tw for some high voltage resistors. somehow missed their array products.what would be the relative tolerance class of UPRNS-13-Type1-10K-A2 that you enquired about?(option T=0.01%) looks the best they have.i understand the min. order quantity is 15 for usd28 each excluding shipping, is it so?i am in if you can ship to pakistan.regards.-zia

author: ramon
author_rank: Regular Contributor
timestamp: December 23, 2017, 02:04:11 pm
content: It was UPRNS-13-Type1-10K-A2-C10. Absolute tolerance ±0.02, and relative TCR ±2ppm/C.I didn't asked for any special relative tolerance, so maybe it is ±0.1%. Not the best for a KVD.MOQ is 50 pcs. But I guess most will order more than one piece. I think it should not be a problem to ship to pakistan :https://www.post.gov.tw/post/internet/U_english/index.jsp?ID=1378161563815

author: zhtoor
author_rank: Frequent Contributor
timestamp: December 23, 2017, 02:08:35 pm
content: Quote from: ramon on December 23, 2017, 02:04:11 pmthank you.external trimming will be necessary in any case unless the relative tolerance is better than 0.0037% for a 1ppm design (Conrad Hoffman's)regards.-zia

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: December 23, 2017, 06:51:13 pm
content: Beware, these resistor types have comparatively high noise levels particularly against precision wire wound resistors. Yes, there is an advantage of tracking with the resistors on a single substrate (not perfect though, watch your power levels carefully) but there are other drawbacks that are also important, tolerance is kind of sloppy. Pay close attention to the other parameters, not just tracking TCR, it isn't the only important parameter. Stability long term for instance, drift with power dissipation and so on. You generally get what you pay for, there are no free rides in high performance resistors.

author: The Soulman
author_rank: Super Contributor
timestamp: December 23, 2017, 08:31:17 pm
content: @ Edwin and others, wouldn't a wire wound resistor with several taps on a common bobbin be best in terms of tempco and long term stability as a (dc V) ratio divider?Because of it is the closed closest way for several resistors to have the same wire/alloy and therefore same tempco and drift?Something similar in construction as the resistors used in the old General-Radio boxes:(On the left)http://www.byan-roper.org/steve/_Media/img_0381.jpeg

author: zhtoor
author_rank: Frequent Contributor
timestamp: December 23, 2017, 09:08:29 pm
content: Quote from: The Soulman on December 23, 2017, 08:31:17 pmprovided the mechanical strains produced by thermal expansion / contraction of the wire is uniform overthe whole winding area...this chain of resistors would be especially easy to tweak using an abrasive to abrade individual sections though.regards.-zia

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: December 24, 2017, 01:54:15 am
content: Re: The Soulman;Yes, it was fairly 'easy' back when Manganin was used and it was solder-able, note that TCRs of very low values were also fairly high, 5- or 10- PPM would be rather exceptional in lower ohms. Evanohm which has proved to be more stable under working conditions has become the main alloy for precision resistors (it is also the same alloy used in film/foil with slight tweaks to the recipe). Since Evanohm must be welded, this complicates the form upon which a multi-resistor could be wound. While I do have bobbin designs which would accommodate two resistors, they are not particularly friendly to production needs. That tends to be the big bottleneck to multi-resistor production, there are no methods in existence as yet which lends themselves to be easy enough to be made on the production floor.....in short, they are too time consuming to be competitive.There have been in the past patents issued for various forms of resistors, including some multi-unit types, in theory they possibly could work but not for production, they are too complicated to build in any kind of volume, the patents are interesting but essentially useless.Indeed, I have been asked quite a few times about multiple resistor designs, it isn't that I don't want to make them, it just isn't as easy as one might think.