cheap precision resistors? - Page 1
Forum section: electronics / projects

author: ralphd
author_rank: Frequent Contributor
timestamp: September 07, 2015, 09:21:00 pm
content: I'm looking for 10-20 precision resistors to make a current reference. The cheapest 0.1% resistors I can find are around 35c ea. While it is cheap in absolute terms, relative to 1% chip resistors, that's about 10x the cost.Is that to be expected?

author: ralphd
author_rank: Frequent Contributor
timestamp: September 07, 2015, 09:27:04 pm
content: Here's the ones I'm thinking of buying:http://m.aliexpress.com/item/32336524608.html

author: JuKu
author_rank: Frequent Contributor
timestamp: September 07, 2015, 09:34:54 pm
content: Yes, that is about right. 10x the precision, 10x the cost. :-)

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: September 07, 2015, 09:43:10 pm
content: Quote from: ralphd on September 07, 2015, 09:27:04 pmI would not trust precision resistors from aliexpress unless you have very good garanties. Moreover, you will not pay more on a reputable provider as Mouser or others.

author: ralphd
author_rank: Frequent Contributor
timestamp: September 07, 2015, 09:56:15 pm
content: Quote from: JacquesBBB on September 07, 2015, 09:43:10 pmIt's the shipping cost that makes Mouser & Newark too expensive. Digi-key may still be an option if I have a reasonable size order, and if they still have $8 shipping to Candada.

author: ralphd
author_rank: Frequent Contributor
timestamp: September 08, 2015, 12:14:56 am
content: Quote from: DiligentMinds.com on September 07, 2015, 11:23:11 pmEast coast. Last time I looked at Future Electronics, they didn't have transparent pricing. I won't setup an account just to find out pricing.

author: rs20
author_rank: Super Contributor
timestamp: September 08, 2015, 12:18:54 am
content: Don't forget that the error in a 1% resistor can trivially be cancelled out in firmware (if applicable) or with a trimpot, whereas temperature coefficient is much harder to deal with. In many of the EEVBlog teardowns of multimeters etc, you see crucial, critical components with 1% or even 10% tolerances; but it turns out that have extraordinarily low drift and tempco for exactly this reason.

author: ralphd
author_rank: Frequent Contributor
timestamp: September 08, 2015, 12:22:19 am
content: Just checked FutureElectronics. Their web site still sucks. No mobile-enabled site, and when I type in a part in the search box and hit enter, nothing happens.

author: ralphd
author_rank: Frequent Contributor
timestamp: September 08, 2015, 12:34:24 am
content: Quote from: rs20 on September 08, 2015, 12:18:54 amI don't have accurate calibration sources, so I need parts with good initial accuracy. With a couple REF5050s and a bunch of tl431s, I hand picked a couple of the tl431s that should be within 0.05% of 2.50V. Then with a 250 Ohm resistor I'll make a simple and cheap 10mA reference.I also want the precision resistors to check the accuracy of my Colluck DMM.

author: ralphd
author_rank: Frequent Contributor
timestamp: September 08, 2015, 01:31:16 am
content: I was all set to get another Newark order a couple months ago until I saw the new shipping rates when I got to the checkout.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: September 08, 2015, 04:57:13 pm
content: The way I proceed with Mouser to avoid shipping fee, is to fill a project list whenever I think I need some parts.Then, when I urgently need a specific part for a project, I just grab whatever I have in my backlist tofill the gap up to 65 $.You just have to be patient, but I found that for many parts (electrolytic caps in particular), Mouser offers better dealsthan ebay, and with reliable parts.What I say about Mouser can of course be translated to any other big company.

author: ralphd
author_rank: Frequent Contributor
timestamp: September 09, 2015, 01:57:56 am
content: Quote from: DiligentMinds.com on September 08, 2015, 04:33:51 pmMost Canadian university classes are > $500 per semester. Even the cheapest community college courses are >$200. On top of that, most courses require you to be admitted to a degree or diploma program.