Author Topic: DIY Low EMF cable and connectors  (Read 50888 times)

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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #125 on: August 03, 2017, 10:14:18 am »
Yeah, that's a bummer!  It just replaces the characters with '?'.

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Offline alm

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Re: DIY Low EMF cable and connectors
« Reply #126 on: August 03, 2017, 11:00:27 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 #127 on: August 03, 2017, 11:08:16 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 #128 on: August 03, 2017, 11:40:14 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

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 #129 on: August 06, 2017, 12:34:45 am »
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #130 on: August 06, 2017, 02:06:34 pm »
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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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #131 on: August 06, 2017, 04:19:32 pm »
I have a question about the payment scheme - I suppose that Alipay is linked with buyers Visa or bank account - can you comment ?

Is there something as AliPay protection if goods do not show up - like there is with Aliexpress ?

Yeah, mine is linked to a Visa card.

Not sure about what sort of protection they have.  I'm actually discovering what ebay's process is right now -- I won an HP 3457A for $150, only to have it apparently delivered to the wrong address by fedex... :(
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Offline onemilimeter

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Re: DIY Low EMF cable and connectors
« Reply #132 on: August 13, 2017, 02:32:55 pm »
Hi...

I found this Teflon (PTFE) cable (shielded, silver plated, 19x0.2mm) from Taobao...
https://world.taobao.com/item/525683103258.htm

The seller wrote it's imported from Japan, manufactured by Junkosha Inc (http://www.junkosha.co.jp/english/)

The outer insulator (brown color layers) is Teflon/PTFE... but I'm not sure about the inner insulator (white color and black color layers)... if I buy it how can I test to tell if it's Teflon/PTFE?

Thanks

« Last Edit: August 13, 2017, 02:40:45 pm by onemilimeter »
 
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #133 on: August 13, 2017, 07:17:51 pm »
I think you could use an electrometer to compare leakage against the same length of some CAT5.  What is the most sensitive current range you have available on your instruments?
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Offline Andreas

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Re: DIY Low EMF cable and connectors
« Reply #134 on: August 13, 2017, 07:22:29 pm »
why not make a simple test with a soldering iron.
Teflon should withstand around 200 deg C.

With best regards

Andreas

 
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #135 on: August 13, 2017, 07:28:27 pm »
bigclive has an interesting way of testing finely stranded wire to see if it is actually copper, or just copper coated aluminum (which apparently is a common cost-saving trick in the ebay junk he loves to review).  If you hold the flame of a lighter against the strands, copper coated aluminum will crinkle up like a dead spider, but pure copper is basically unaffected.
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Offline onemilimeter

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Re: DIY Low EMF cable and connectors
« Reply #136 on: August 13, 2017, 09:39:06 pm »
I think you could use an electrometer to compare leakage against the same length of some CAT5.  What is the most sensitive current range you have available on your instruments?

I may have access to a Keithley 2002. Can this instruments do the job? Thanks.
 

Offline SeanB

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Re: DIY Low EMF cable and connectors
« Reply #137 on: August 13, 2017, 09:52:27 pm »
Strip an end and use a lighter. If it burns it is PVC or some other plastic, and if it just chard and makes a noxious smoke it is PTFE.

Likely though if the outer sleeve is PTFE the inner is as well, as that type of cable is common in avionics as a data wire or shielded cable for low level signals.
 
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #138 on: August 16, 2017, 01:07:25 pm »
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.

Welp, the first set arrived.  It looks like they are gold-plated brass, although they almost feel too light to be brass.  (I filed off the outer plating, and the surface and shavings have the appearance of brass).

I wonder if there is an easy chemical test to check for brass?  I know that copper will turn some acids bright blue...

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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #139 on: August 16, 2017, 01:13:00 pm »
So after watching this Transmille video where he demonstrates using a null voltmeter to directly measure a thermal EMF, I decided to take the plunge and bought an HP 419A on ebay.

https://youtu.be/KiYhEP6m7Pc?t=1m23s

In a few weeks I hope to be able to measure thermal EMFs directly!

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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #140 on: August 16, 2017, 01:18:39 pm »
So after watching this Transmille video where he demonstrates using a null voltmeter to directly measure a thermal EMF, I decided to take the plunge and bought an HP 419A on ebay.

https://youtu.be/KiYhEP6m7Pc?t=1m23s

In a few weeks I hope to be able to measure thermal EMFs directly!
buy keithley 155 or Fluke 845 is better
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Offline ManateeMafia

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Re: DIY Low EMF cable and connectors
« Reply #141 on: August 16, 2017, 01:22:41 pm »
My money says it's brass. I am more interested in finding out what they used for the external plating.

A null meter is invaluable and at least the seller gives a 14 day warranty. You may want to see what kind of chopper amp was used but I have recently taken photos of an ESI 801 and it used the HP 419 as the null meter. very nice looking inside.
 

Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #142 on: August 16, 2017, 01:35:16 pm »
buy keithley 155 or Fluke 845 is better

Yeah, I did a bit of homework.  Those are nicer units, but they are out of my "splurge" price range (they are $200+ on ebay at the moment).

There are a lot of Leeds & Northrup models for ~$50, but their lowest range is 1mV.

The 419A's lowest range is 3uV, and the price was right, so that's the one I settled on.

(I think a fun project might be to see if you can get a Leeds & Northrup unit for $25 using "best offer", then gut it and install Conrad Hoffman's null detector circuit from his mini-metrology-lab article series)
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #143 on: August 16, 2017, 01:40:19 pm »
I wonder if there is an easy chemical test to check for brass?  I know that copper will turn some acids bright blue...

Hmm...

Quote
Apply a small amount of hydrochloric acid to an area of the brass. Test only a small area because the test is corrosive. Unlike some metals, brass turns pink when it is tested with hydrochloric acid.

via http://ourpastimes.com/identify-brass-metal-8529918.html
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #144 on: August 16, 2017, 01:52:48 pm »
I bought some copper spade lugs from China ,not bad.

Great find!  I've been searching for unplated copper spades, but haven't had any luck.  Can you reveal a link to where you found these?
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #145 on: August 16, 2017, 02:03:41 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.

My first victim to go into the citric acid bath was a cheap "logico" banana plug, which appear to be a clone of Nakamichi banana plugs.

A few days into the acid, the body of the connector started to take on a reddish hue, and I thought they might actually be copper.

However, after about another week, and after taking them out of the acid for a while, they were a much darker, brownish color.  Filing away the body reveals what looks like brass.
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #146 on: August 16, 2017, 02:54:44 pm »
I took interest in the "logico" plugs because I was trying to get away from plugs which had a loose-fitting free-spinning contact barrel-spring.  The logico plugs were of a style where the contact spring was attached solidly to the body, which I thought would be better for precision measurements.

Then, while searching for unplated copper banana plugs, I came across the plugs marketed at audiophiles:

http://www.douglasconnection.com/Furez-TSTSB60NP-Bare-Copper-Banana-Plug-Connectors-Pair-FZTSTSB60NP.htm

I liked the design of these plugs even better, as they were a single, solid piece of material, and it seemed there would be even more surface area in contact with the DMM's socket.  They also claimed to be tellurium copper, so even though they are priced for audiofools, I decided to order a pair for use as a low thermal EMF "benchmark".

Then, just this evening, I stumbled upon the fact that this style of connector has a name.  If you search for "BFA banana", you'll find plugs like this.

https://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Delectronics&field-keywords=bfa+banana

https://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=bfa+banana&_sop=7

https://www.aliexpress.com/wholesale?&SearchText=bfa+banana

Taking it a step further, you'll find plugs marketed as "low mass", which appear engineered to have a little mass as possible.  This also seems desirable for minimizing thermal EMF's.

I managed to find an ebay seller who sells unplated copper "low mass" BFA-style banana plugs, and I've just ordered a few.  They are just under $3 each, so not cheap but also not audiofool-priced.  I'll keep you posted!

http://www.ebay.com/itm/162631332431

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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #147 on: August 16, 2017, 03:08:19 pm »
Here's a better shot, comparing the color of tellurium copper, the dark de-plated connector, a filed off section, and a "gold" plated original connector.

(the red pliers, blue matt, and white paper are to help with white balance.  capturing metal in a photo without turning it into a mess of glare is hard!).
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Offline MisterDiodes

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Re: DIY Low EMF cable and connectors
« Reply #148 on: August 17, 2017, 12:49:12 am »
Just a head's up since this is metrology section: "Precision" connector as in chasing low ppm measures (if that's what you're doing) means no banana plugs; just use a -clean- direct wire connection to binding post whenever possible.  The best low emf connections for low-ppm precision are clean copper to clean copper - or for easier cleaning the use of gold plated copper (typically will be gold flash over nickle over copper) connections are good also.

Using a -clean- piece of solid copper wire slipped into the cross hole of a binding post really is relatively good "precision" connection and is considered better than any slip-in banana plug style.  "Shrouded" banana plugs and sockets are not going to help low ppm measures.

You'll see this inside a lot of null meters, and learn the manufacturing nuance:  The inside connection to the binding copper post is usually a spade connector under a couple nuts on the threaded shaft (not soldered), usually gold plated and crimped spades.  If you make the -same-  type of connection with the same material on the external part of the binding post, you've basically cancelled most thermal EMF effect right there at one binding post (both end connections at the same post of same material combination at same temp cancel out thermal emf).  Any other unbalanced thermal effect is greatly reduced by keeping the binding posts at the same temp.

The general problem with something like a raw solid copper male banana plug is A) They always need to be cleaned of oxide before use and B) they are fairly soft, wear easily and tend to lose their spring-contact force - and that means it's harder to get a repeatable connection the more the connector is used.  So that means you'll keep these for your more "special" setups, not for everyday general use.

That's why for a general use: a good spring-rate brass alloy (with overplate nickel / tin / gold) is typically used for any connector requiring a spring force on the metal to metal contact area - that means longer contact life / more mating cycles.

If you're using a plain copper banana plug, ideally that would slip into a plain copper socket - but that socket would be a bit harder to keep clean.  The worst connection you could make for a "precision" setup is copper on oxide!

The worst banana plugs for high precision repeatable measures would be the type with the loose spinning plug end - the solid style like you found is better.

Those setscrews on the side of the banana plug are a place for problems to start especially if you're using stranded wire.  Keep an eye on that.  Wire strands have a really bad habit of wiggling out from under setscrews, and if these leads would see a lot of use we'd use a copper ferrule crimped onto the stranded wire wherever it's going to be under simple screw clamps like that.   

« Last Edit: August 17, 2017, 03:16:37 am by MisterDiodes »
 
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #149 on: August 17, 2017, 04:17:46 am »
Thanks MisterDiodes, that's great advice.

My hunt for the perfect banana plug is in an attempt to solve the budget metrologist's problem of "my best meter has banana sockets, not binding posts".  That budget metrologist will never be able to achieve a "perfect" setup, but given that, the question is "how close can they get?".

For example, the 34401A (if you can find one under $250) represents a very good bargain for the budding volt-nut, but sadly, only comes with banana sockets.  In spite of that, the budding volt-nut is someone I want to support in their quest, and hopefully I'll come up with some useful findings!   8)
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