Author Topic: DIY Low EMF cable and connectors  (Read 119036 times)

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Offline dl1640

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Re: DIY Low EMF cable and connectors
« Reply #200 on: January 22, 2018, 11:57:54 pm »
--
Another way that works well:  the cal lab room is supplied with a full isolation transformer and it's own safety circuit breaker distribution box coming off the transformer secondary:  In that situation (a.k.a. an Island AC System) it was able to have it's very own ground rod array right smack dab in the middle of the lab room floor.  Because it was an AC power system completely galvanically isolated from the utility grid, it was able to have a completely -local and isolated- grounding system - and it was setup to run on its own battery / inverter supply also.  24VAC and 48VDC supplied to test benches directly which is nice for lab use,  and to keep things extra extra quiet the overhead lighting switches to 12 and 24VDC halogen incandescent.  Nice.  You could run LED lighting also as long as no switching power supply used, but halogens provide the best CRI.
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Hi Mr Diodes

It looks "island ac system" is the best while it is not so easy for us to achieve.
I looked into some national codes, the ac system from utility co. is TN-S, TN-C, TN-S-C, TT...each one has different grounding point..so I'd think better to connect breaker panel ground and utility ground to lab ground then to the EARTH, if lab ground is really the EARTH..
 

Online beanflying

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Re: DIY Low EMF cable and connectors
« Reply #201 on: February 08, 2018, 06:33:19 am »
Before I strip these someone suggested they may be silver plated not nickel? Anyone seen these or know of them or know a good way to tell silver from nickel?

I suspect based on the cloth wiring and string looming 50's vintage is likely.



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Offline kj7e

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Re: DIY Low EMF cable and connectors
« Reply #202 on: February 08, 2018, 02:36:07 pm »
Use some silver polish on one of them and see if it shines up nicely.  You will also have a black residue on the cloth you use.  The effect will be very pronounced if they are silver and not nickel.  Just from the photo, they have that silver plated look to them.
 

Online beanflying

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Re: DIY Low EMF cable and connectors
« Reply #203 on: February 10, 2018, 06:34:15 am »
And the consensus of two silver jewelers including a chemical test was Silver plated  :-+ So 22 silver plated Copper terminals at $15 AUD total spend is not a bad purchase  :D
Coffee, Food, R/C and electronics nerd in no particular order. Also CNC wannabe, 3D printer and Laser Cutter Junkie and just don't mention my TEA addiction....
 

Offline JDubU

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Re: DIY Low EMF cable and connectors
« Reply #204 on: February 25, 2018, 10:34:11 pm »
FYI:

You can very quickly remove silver tarnish with a simple chemical reaction that works amazingly well and does not remove any silver.  It converts the tarnish back to elemental silver.

http://blog.teachersource.com/2014/01/18/chemistry-of-tarnished-silver/
http://www.compoundchem.com/2013/12/16/removing-tarnish-silver/



Do it outside though.  It can produce a small amount of hydrogen sulfide gas (toxic).
« Last Edit: February 25, 2018, 10:45:19 pm by JDubU »
 
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Offline cellularmitosis

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Re: DIY Low EMF cable and connectors
« Reply #205 on: April 27, 2018, 04:36:24 am »
I took a chance on taobao looking for some kelvin clips.

I ordered these: https://item.taobao.com/item.htm?id=563805376375

But after filing them down, they appear to be some sort of steel.

However I also ordered these: https://item.taobao.com/item.htm?id=540555760189

And after filing an edge down they appear to actually be copper underneath whatever the plating is.


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Offline quarksTopic starter

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Re: DIY Low EMF cable and connectors
« Reply #206 on: April 27, 2018, 08:15:04 am »
I ordered these: https://item.taobao.com/item.htm?id=563805376375

But after filing them down, they appear to be some sort of steel.

have you checked with a magnet if they are steel?

I am asking because I have similar Kelvin Clips and they seem to be of good quality.
Attached is a pic. of another alternative which I find good

https://www.banggood.com/de/2Pcs-Copper-Gwinstek-LCR-Kelvin-Test-Clip-Bridge-Test-Clip-Microresistivity-Clip-p-1043337.html?cur_warehouse=CN

 

Offline Echo88

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Re: DIY Low EMF cable and connectors
« Reply #207 on: June 22, 2018, 10:34:51 pm »
I may have overlooked the fitting post in this thread, but can someone please point me to a shop (couldnt find them on taobao) where i can find those copper spade lugs for little money?
 

Offline ManateeMafia

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Re: DIY Low EMF cable and connectors
« Reply #208 on: June 23, 2018, 12:43:09 pm »
The last link that I had seen was for thermocouple spades. A quick search found some that were not wide enough for binding posts...

I did find these but they are not cheap  http://www.edl-inc.com/Copper-Gold-Plated-Instrument-Lugs-25-Qty_p_51.html


 

Offline dr.diesel

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Re: DIY Low EMF cable and connectors
« Reply #209 on: June 23, 2018, 04:21:39 pm »
I did find these but they are not cheap  http://www.edl-inc.com/Copper-Gold-Plated-Instrument-Lugs-25-Qty_p_51.html

Dang, they also want $25 to ship a pack of lugs.

We could probably get a batch cut for the community here cheaper.


Offline JohnG

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Re: DIY Low EMF cable and connectors
« Reply #210 on: June 23, 2018, 10:58:27 pm »
Maybe these will work: http://www.surplussales.com/Connectors/banana.html

Look on the page for "Gold Binding Post"



Don't know anything about them, haven't cut one open, but worth a look.

John
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Offline Kosmic

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Re: DIY Low EMF cable and connectors
« Reply #211 on: June 24, 2018, 12:41:41 am »
Look like ground/guard binding post (no insulation).

There is tons of cool stuff on that store thought. Thanks for sharing!
 

Offline Vgkid

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Re: DIY Low EMF cable and connectors
« Reply #212 on: June 24, 2018, 01:16:36 am »
Those are ESI non insulated binding posts. Often used for grounds on the ESI gear.
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Offline EmmanuelFaure

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Re: DIY Low EMF cable and connectors
« Reply #213 on: June 24, 2018, 11:06:05 am »


"Originally made in 1943, then re-packed in 1963"

OMG! They're beautiful.
 

Offline Magnificent Bastard

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Re: DIY Low EMF cable and connectors
« Reply #214 on: June 25, 2018, 06:14:44 pm »
Maybe these will work: http://www.surplussales.com/Connectors/banana.html

Look on the page for "Gold Binding Post"



Don't know anything about them, haven't cut one open, but worth a look.

John

GREAT find!  Thanks for that!
 

Offline Echo88

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Re: DIY Low EMF cable and connectors
« Reply #215 on: June 28, 2018, 09:26:41 am »
Regarding the Amphenol plugs "ait6e16-11pc-b30" which fit nanovoltmeters like the Keithley 181 or 148 and which are mentioned by CalMachine on page 8:

I ordered two of them from Arrow Electronics, filed a bit on one of the connector-pins and found out they are made of brass instead of copper. Also: the product specification code doesnt include the statement that the pins are explicitly made of copper. Its just mentioned in the datasheet for the AIS-series: "made of brass or copper alloy".

I will build one shorting plug and one measurement cable from the plugs and test them against my old measurement cable which i did buy with my K181 regarding thermal emf.
 

Offline CalMachine

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Re: DIY Low EMF cable and connectors
« Reply #216 on: June 28, 2018, 12:30:45 pm »
Regarding the Amphenol plugs "ait6e16-11pc-b30" which fit nanovoltmeters like the Keithley 181 or 148 and which are mentioned by CalMachine on page 8:

I ordered two of them from Arrow Electronics, filed a bit on one of the connector-pins and found out they are made of brass instead of copper. Also: the product specification code doesnt include the statement that the pins are explicitly made of copper. Its just mentioned in the datasheet for the AIS-series: "made of brass or copper alloy".


You should contact Amphenol about that.  After many phone conversations with them, explicitly stating I needed copper pins, that is the part number they gave me.  Perhaps their own sales people weren't aware of the "Brass or Copper alloy" statement within the datasheet.

I'm a little upset to learn the pins are actually brass.  I hadn't ordered enough quantity to do any material testing on, so I took their word for it.   :rant:
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Offline martinr33

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Re: DIY Low EMF cable and connectors
« Reply #217 on: June 29, 2018, 02:27:46 am »
The datasheet on Mouser for that connector states "copper alloy". No mention of brass. They are silver plated.

I did grind a little off of a Mouser part. The color matches the reddish color of a copper clip that I have, and is not the bright yellow of brass.

There again, the pins sit deep inside the connector and are well-shielded from air. The K182 gets quite warm, especially at the connector.
 

Offline Echo88

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Re: DIY Low EMF cable and connectors
« Reply #218 on: July 02, 2018, 07:35:45 pm »
@ martinr33: Could you please provide the datasheet you mentioned? I couldnt find it on mouser, only on Peigenesis: http://www.peigenesis.com/images/content/pei_tabs/amphenol/ait-ms-series/new-thumbs/025-048_ait-ms_series.pdf which claims "Copper Alloy or Brass" as far as i could see. My measurements of the freshly made cables made from the connectors with brass were conducted at varying room temperature and therefore leave a lot to be desired:

In the attachment: mV means nV, measured at the Analog Output from the K181
I build a thermal short from one connector (with a copper conductor from the same cable i use for the next measurement cable) and crimped one connector to a screened copper cable of 3m, which ends i stripped and twisted  and then crimped them together. I let my K181 settle with the newly built thermal short and at about 13h i changed it to the newly built measurement cable with the crimped ends. One can see the <30nVpp noise with the thermal short plug, like advertised in the K181-datasheet. After the 13h-mark the temperature varies, since im about 1m away from the K181, playing at the PC.

I might buy a A23-amplifier from EM-Electronics and put it in an oven and enjoy the 1.5nVpp noise, without bothering for expensive plugs, since one can always just solder another twisted-pair-cable to the A23.  :popcorn:
 

Offline JohnG

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Re: DIY Low EMF cable and connectors
« Reply #219 on: July 05, 2018, 06:43:08 pm »
Just as a reminder, brass is a copper alloy. If I saw the phrase "copper alloy", I would not rule brass out unless the alloy was further specified. Just my $0.02.

John
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Offline martinr33

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Re: DIY Low EMF cable and connectors
« Reply #220 on: July 10, 2018, 01:05:31 am »
Connector datasheet. As noted, I ground some of the plating off and saw the reddich color of copper, not the yellow of brass.

https://www.mouser.com/datasheet/2/18/12-020-462735.pdf

In working with these connectors and the K182, the connectors don't seem to be an issue.

I've seen some odd thermal effects (maybe 100nV rise from warming one leg of my differential cable). Odd, becasue I cannot explain them. They should balance, but they don't.
 

Offline Echo88

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Re: DIY Low EMF cable and connectors
« Reply #221 on: July 10, 2018, 08:38:46 am »
I cant find the "AIT"-connector in your pdf. But it seems copper-contacts are always silver plated and brass ones gold plated.
Anyway, my tests with my selfbuild-cables are good so far, but are limited by the K181 itself regarding resolution and noise/short term stability.
I hope i find a case were i really need a good nanovoltmeter to finally buy a A23-module.  ;D
 

Offline JohnG

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Re: DIY Low EMF cable and connectors
« Reply #222 on: July 10, 2018, 02:31:49 pm »
A few more things:

The vast majority of gold plating on copper uses a nickel barrier layer plated on the copper first, and this is then plated with gold. The nickel layer is used to prevent copper diffusion into the gold, which can lead to tarnish on the surface.

I think this is less of an issue with silver, but then again silver can tarnish on its own.

If you have a powerful rare earth magnet, you can often tell if there is a nickel barrier coating by suspending the plated object from a thread and placing the magnet near it. You can see a slight deflection due to the nickel layer. If the plated object can be spun easily on a flat (nonmagnetic) surface, you can also use a rare earth magnet to deflect it slightly.

One other word of warning. Brass is supposed to be a copper-zinc alloy, but it is often contaminated with other metals, including iron. Sometimes there is enough contamination that you can pick up the "brass" with a powerful magnet.

John

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Offline dl1640

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Re: DIY Low EMF cable and connectors
« Reply #223 on: July 12, 2018, 11:05:34 am »
I got a small loop of single-strand 24AWG pure copper wire with PTFE insulation. The seller left a tag on the wire indicating the *signal direction*. When measuring low level voltage, shall I wire the cable with regard to the signal direction sign?

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Offline TiN

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Re: DIY Low EMF cable and connectors
« Reply #224 on: July 12, 2018, 02:22:13 pm »
Quote
The seller left a tag on the wire indicating the *signal direction*. When measuring low level voltage, shall I wire the cable with regard to the signal direction sign?

 :popcorn: Sounds like audiofoolery to me  :-DD
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