Author Topic: DIY Low EMF cable and connectors  (Read 119015 times)

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Offline MisterDiodes

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Re: DIY Low EMF cable and connectors
« Reply #100 on: June 27, 2017, 03:42:29 pm »
TiN: I showed your test setup to a colleague who works at the IC level doing analog designs, and spends a lot of time looking at thermal junction effects.  He cautions that your test setup is going to also measure the cancelling effect of the second connection to the binding post:  You've got the threaded end with your sample spade and/or clean copper wire, but if you have a second connection of a soldered copper wire onto the base of the binding post that's going to cancel out the threaded end junction to some extent.

He also cautions that you will find out if that amp internally and cable / test jig has thermal-balanced connections throughout.

One technique that's used to test a specific connection combination is you make a sample threaded end on a much longer rod of whatever material - and then put a thermocouple on the threaded end and a second thermocouple on the end where you have a soldered wire to complete the test circuit voltage pickup loop.  Now you have a way to monitor the temp. of each junction, without any other junctions in between.  That way you can have both ends of the rod at different temperatures and thus isolate the effect of -one- junction over the other.  You won't be able to do that on a short binding post, the ends are too close together to get a decent temp. spread, probably.

If you think you see a thermal EMF, it's a good idea to swap all connections to reverse DUT junction connections and make sure you are really seeing a mirrored voltage level.

Again:  The main practical strategy in general is to keep all connections at the same temp. and consistent, and then most thermal effects -should- cancel out to a great extent a lot of times - at least below the noise level of whatever other test is going on.  If you keep your binding posts / sockets in thermal balanced pairs and sharing the same temperature, it shouldn't matter too much what they are made of - to a certain level of measurement uncertainty.

That's the theory.  You will find the junction where reality steps in. :)





 
« Last Edit: June 27, 2017, 03:49:36 pm by MisterDiodes »
 
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Offline MK

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Re: DIY Low EMF cable and connectors
« Reply #101 on: June 27, 2017, 04:08:15 pm »
The EM electronics A10 amplifier does have pure copper thermally balanced connectors and has about 1nV rt hz all the way to dc.

 
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Offline Ash

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Re: DIY Low EMF cable and connectors
« Reply #102 on: June 29, 2017, 11:54:19 pm »
Hi everyone,

I also received my order of copper binding posts from the Taobao seller. It took 2 weeks to deliver here in Australia, which is pretty good for stuff from China (normally takes a month).

I'm pretty happy with the quality and as TiN has shown these appear to be a reasonable copy of the Pomona 3770. See the photo.

The finish seems to be raw copper, unlike the Pomona ones which are gold flashed. I suspect I may need to invest in some deoxit. :) Also the Pomona items retain the thumb screw, but that is fine. They fit Pomona banana plugs well, but I'll be using them with solid core wires I expect.

One of mine has a slightly bent end where the hole is, looks to be a manufacturing defect. Nothing that will affect the unit in use.

So I'm pretty happy with these, especially for the price. Taobao is a bit daunting for the non-Chinese speaker, but I found you can use the "always translate" feature in Chrome and muddle your way through. Essentially it is just like eBay, make the purchase, get the goods and evaluate them. The Alipay service also holds the payment in escrow until you release it. So if you order and are happy, make sure you complete your end of the transaction :)

Cheers,
Ash.

EDIT: the Pomona 3770 is lower left in the photo, the remaining ones are the ones I received from Taobao.
« Last Edit: June 29, 2017, 11:58:24 pm by Ash »
 
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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #103 on: June 30, 2017, 01:33:02 am »
I have some binding posts collection, the most i like are these two.
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Offline Echo88

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Re: DIY Low EMF cable and connectors
« Reply #104 on: August 02, 2017, 12:34:45 pm »
Maybe some of you guys find this trick useful:

I threw some normal crimp spade lugs in citric acid and after 2 weeks the relevant tin layer was etched away, yielding lowest cost pure copper (according to an exemplary manufacturer >99,9% electrolytic copper) spade lugs suitable for nanovolt-stuff.
Of course hydrochloric acid and oxygen peroxide would etch way faster, but i didnt have that stuff lying around.
 
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #105 on: August 02, 2017, 02:16:48 pm »
Very interesting Echo88!  I think I'll try that myself.

Would something like this work?  Powdered food-grade citric acid?  https://www.amazon.com/gp/aw/d/B00EYFKKZC/ref=sxts_sxwds-tsp_1_a_it?ie=UTF8&qid=1501683294&sr=1

TiN, 0.01C, can you guys post a link to the taobao seller who sells those binding posts?  I'd like to order some.
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Offline Echo88

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Re: DIY Low EMF cable and connectors
« Reply #106 on: August 02, 2017, 04:08:43 pm »
I used a descaler which contained citric acid, so the mentioned pure citric acid in a solution should work even better i think.
 
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Offline pelule

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Re: DIY Low EMF cable and connectors
« Reply #107 on: August 02, 2017, 05:18:10 pm »
Following low EMF cable (or similar with 4mm plugs) are offered at the bay.
A single cable offered some weeks ago first time (@~70 EUR and free shipping) - a "trial" ?
Now several cables offered from same seller (49,96 EUR + 21,17 EUR shiiping inside Germany == same price, ridicolous shipping cost).
http://www.ebay.de/itm/Low-EMF-Test-Cable-PTFE-4-wire-shielded-e-g-for-Datron-1281-Agilent-3458A/263097836230?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649
The cables look like selfmade.
Has anyone experiance with that cables.
/PeLuLe
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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #108 on: August 02, 2017, 05:34:54 pm »
 :-+ Great
« Last Edit: August 02, 2017, 05:53:43 pm by 0.01C »
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Offline pelule

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Re: DIY Low EMF cable and connectors
« Reply #109 on: August 02, 2017, 07:21:08 pm »
Hi Flintstone,
stupid me, I was not able to link "ab-pr" at the bay with Adrian, wich I know personally.
Thanks for getting me back on track.
/PeLuLe
You will learn something new every single day
 

Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #110 on: August 02, 2017, 11:21:48 pm »
I just find a shop selling nice binding posts,
https://world.taobao.com/item/521116800640.htm?spm=a312a.7700714.0.0.2LAU7Z#detail

It looks like that link goes to some vishay resistors.  Can you post the link again?  Thanks!
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Offline 0.01C

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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #112 on: August 02, 2017, 11:35:40 pm »
use chrome app to translate
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #113 on: August 02, 2017, 11:37:37 pm »
Ah, thanks for the tip.

Do you also have a link to the banana plugs which are all one piece and have the cross-shaped cutout?  I tried searching for those based on the description, but nothing came up.
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Offline EmmanuelFaure

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Re: DIY Low EMF cable and connectors
« Reply #114 on: August 02, 2017, 11:45:09 pm »
$3.72 is for one piece?
 

Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #115 on: August 03, 2017, 12:04:29 am »
$3.72 is for one piece?

Yup.

I've never been able to checkout successfully when using taobao directly (something seems to flag me at the captcha), but I threw 8 of them into my cart just to see what would happen, and lo and behold, it worked!

I ordered 4 red, 4 black, for 200 yuan + 40 yuan shipping, which works out to about $3.72 each + $5.95 shipping.

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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #116 on: August 03, 2017, 12:09:53 am »
Ah, thanks for the tip.

Do you also have a link to the banana plugs which are all one piece and have the cross-shaped cutout?  I tried searching for those based on the description, but nothing came up.
https://s.taobao.com/search?q=???&type=p&tmhkh5=&spm=a21wu.241046-us.a2227oh.d100&from=sea_1_searchbutton&catId=100
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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #117 on: August 03, 2017, 12:11:03 am »
oh , eevblog can not show the chinese word
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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #118 on: August 03, 2017, 12:12:11 am »
Ah, thanks for the tip.

Do you also have a link to the banana plugs which are all one piece and have the cross-shaped cutout?  I tried searching for those based on the description, but nothing came up.
pm your email address to me , i send the taobao link to you
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #119 on: August 03, 2017, 12:14:18 am »
Yeah, that's a bummer!  It just replaces the characters with '?'.

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Online alm

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Re: DIY Low EMF cable and connectors
« Reply #120 on: August 03, 2017, 01:00:27 am »
I thought we solved this problem years ago with Unicode. But apparently Unicode is too difficult for SMF or the database setup.

You might be able to use a link shortener like tinyurl.com/ or goo.gl.

Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #121 on: August 03, 2017, 01:08:16 am »
I found two plugs which appear to be the same style (one solid chunk of copper with a threaded end):

https://world.taobao.com/item/529066733817.htm

https://world.taobao.com/item/550387066144.htm

I've ordered a few of each.  When they arrive, I'll cut into one of them (or try the citric acid trick) to see if they are really copper inside.

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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #122 on: August 03, 2017, 01:40:14 am »
I found two plugs which appear to be the same style (one solid chunk of copper with a threaded end):

https://world.taobao.com/item/529066733817.htm

https://world.taobao.com/item/550387066144.htm

I've ordered a few of each.  When they arrive, I'll cut into one of them (or try the citric acid trick) to see if they are really copper inside.
Try this[emoji12]

https://world.taobao.com/item/36025097741.htm?fromSite=main&spm=a230r.1.14.19.ebb2eb27o1fGJ&ns=1&abbucket=17#detail

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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #123 on: August 05, 2017, 02:34:45 pm »
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #124 on: August 06, 2017, 04:06:34 am »
Hello VoltNuts - As some of the VoltNuts live in europe and we see all these nice products on TaoBao - can someone explain the details how to order from Taobao - most of us do cannot read chinese language ... how to become member of Taobao as a customer living in europe and what are the options we have to pay (VISA, PayPal, ... ?)

Fred,

My first experience was with a Taobao "agent" (it was https://taobaofocus.com/ ), which is an english-language website where you give them the item numbers (from the taobao.com URL), and they buy the items and then ship it to you.  This seemed convenient, but they tack on a ~30% fee, and then on top of that you have to pay rather expensive shipping (on top of whatever it cost to have the items shipped to them first).  This meant that the salvaged LM399 references I found for ~$3.00 each ended up being the same cost as the ~$6.00 units available on ebay, which defeated the whole point of using taobao.

Next, I used taobao.com directly.  I used the translate feature of google chrome to mostly muddle my way through the sign-up process, and creating an alipay account (which is like a chinese paypal), shopping, and placing an order.  There were a few screens which chrome didn't seem to be able to translate, and for those I had to install the google translate app onto my iphone, which allowed me to point my phone's camera at my laptop screen and perform the translation.  Additionally, there are a lot of taobao listings which have text baked into images, which chrome can't translate, but the phone app can.

In general, there's a very big "I have no idea if this is going to work" aspect to all of this, and you have to be willing to take a risk.  For example, my first order was about 5 different items, 3 of which have shipped, and 2 of which have had no response from the seller in about 5 days (pity, one of those was an LT1088 for only $18 -- perhaps that was too good to be true).

Best of luck!
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