Author Topic: DIY Low EMF cable and connectors  (Read 118982 times)

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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #175 on: September 26, 2017, 02:49:48 am »
I've ordered a bunch of these copper binding posts (https://world.taobao.com/item/40823926055.htm), but it seems I did something wrong on Taobao - should learn more languages.
The order was paid correctly (VISA), including the shipping (2 x 40 yuan for that) and sent by the seller but the parcel is still in Shenzen for the last two weeks (LX480192824CN).

Did anyone encounter the same problem?
I just send your message to the taobao seller , you can file a item not received case on taobao to get full refund.
« Last Edit: September 26, 2017, 02:52:58 am by 0.01C »
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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #176 on: September 26, 2017, 03:00:48 am »
Seller reply your item is on the way now , the tracking detail update very slow ,please wait some more days
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Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #177 on: September 26, 2017, 03:07:55 am »
Seller will reply you here
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Offline Squantor

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Re: DIY Low EMF cable and connectors
« Reply #178 on: September 26, 2017, 07:44:17 am »
Procured some parts to make a cable for older Keithley NanoVoltmeters (180,181,182).  There are other models that use the same type of military style connector, as well

Connector - AIT6E16-11PC-B30 (Gold Plated, Copper Alloy, Crimp connection)
Cable - Belden 5500FE (~1.5m)
Spades - Bare copper crimp spades


Where did you get the  AIT6E16-11PC-B30 from? I have been looking for a solution for my Keithley 150B for ages.
 

Offline lukier

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Re: DIY Low EMF cable and connectors
« Reply #179 on: September 26, 2017, 07:48:36 am »
Buy the  binding posts from taobao,you can through Taobao tools "wangwang"contact the seller,see that

Seller reply your item is on the way now , the tracking detail update very slow ,please wait some more days

Thanks guys, it is some strange glitch with the tracking.
Unfortunately, Wangwang Chat in the Chrome browser never worked for me and the standalone client is only for Windows, so I couldn't contact the seller.
« Last Edit: September 26, 2017, 10:13:44 am by lukier »
 

Offline 0.01C

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Re: DIY Low EMF cable and connectors
« Reply #180 on: September 26, 2017, 07:11:10 pm »
Buy the  binding posts from taobao,you can through Taobao tools "wangwang"contact the seller,see that

Seller reply your item is on the way now , the tracking detail update very slow ,please wait some more days

Thanks guys, it is some strange glitch with the tracking.
Unfortunately, Wangwang Chat in the Chrome browser never worked for me and the standalone client is only for Windows, so I couldn't contact the seller.
your item is arrived in the UK.
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Offline lukier

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Re: DIY Low EMF cable and connectors
« Reply #181 on: September 26, 2017, 07:46:37 pm »
your item is arrived in the UK.

Yup, just today. Thanks! Just normally there are some tracking events in order, like post office received, transit, airport arrival, leaving airport to overseas etc before it reaches Heathrow. Lack of any extra events and tracking saying the parcel is still in Shenzen got me worried.

Thanks again for all the help. Hopefully Duolingo will introduce Chinese soon, so I can learn a bit :)
 

Offline CalMachine

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Re: DIY Low EMF cable and connectors
« Reply #182 on: September 26, 2017, 08:17:46 pm »
Procured some parts to make a cable for older Keithley NanoVoltmeters (180,181,182).  There are other models that use the same type of military style connector, as well

Connector - AIT6E16-11PC-B30 (Gold Plated, Copper Alloy, Crimp connection)
Cable - Belden 5500FE (~1.5m)
Spades - Bare copper crimp spades


Where did you get the  AIT6E16-11PC-B30 from? I have been looking for a solution for my Keithley 150B for ages.

It is an Amphenol MS3106E16-11P connector and the gold plated/copper crimp version is the part number I listed (AIT6E16-11PC-B30).
The local distributor I used is PEI Genesis.  You might need to get ahold of Amphenol and find out who your local distributor is.
« Last Edit: October 01, 2017, 03:04:28 am by CalMachine »
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Offline branadic

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Re: DIY Low EMF cable and connectors
« Reply #183 on: September 30, 2017, 11:39:46 pm »
Sorry to hack this thread, but maybe someone in here can help. Were can I get those security gold plated copper posts used in many multimeters such as Keithley, Prema and so on? What I found up to now is always gold plated brass, but I'm pretty sure Keithley won't use brass in their 2002 model, do they?



I need them for a low thermal emf, low noise application (2x black, 2x red). Thanks for your help.

-branadic-
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Offline lukier

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Re: DIY Low EMF cable and connectors
« Reply #184 on: October 01, 2017, 12:03:52 am »
Sorry to hack this thread, but maybe someone in here can help. Were can I get those security gold plated copper posts used in many multimeters such as Keithley, Prema and so on? What I found up to now is always gold plated brass, but I'm pretty sure Keithley won't use brass in their 2002 model, do they?

Security banana sockets and low-EMF don't usually go hand in hand.

I too couldn't find the particular ones used by Keithley, gold and with the pin-sleeve mount on the back. This one looks the most similar in shape and form, but it is brass+nickel:
http://www.caltestelectronics.com/ctitem/91-jacks-banana-jacks/CT2912

If you don't need the Keithley like connectivity on the back and this is for one-off project I would recommend buying 34401A input block part from Keysight (part number 34401-62121).  Not crazily expensive and you get five tellurium copper banana sockets, going straight to the PCB.
 

Offline The Soulman

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Re: DIY Low EMF cable and connectors
« Reply #185 on: October 01, 2017, 09:43:19 am »
Hirschmann has those: (gold plate over brass)

https://www.reichelt.com/de/en/4mm-Jacks/SEP-2630-S19-SW/3/index.html?ACTION=3&LA=446&ARTICLE=130849&GROUPID=5629&artnr=SEP+2630+S19+SW&SEARCH=hirschmann%2Bgold

I did ask before but will ask again, how does the base material matter at all (for sub micro Amps) if the gold plate is all around?
 

Online Echo88

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Re: DIY Low EMF cable and connectors
« Reply #186 on: October 01, 2017, 10:03:33 am »
He did ask for gold plated copper ones, not brass. And this matters for very high accuracy voltage measurements because of the thermal emf voltages generated by the jacks. All the electrons flow through the volume of the jack, not on the gold plated surface, therefore copper as base material is necessary.
 

Offline VK5RC

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Re: DIY Low EMF cable and connectors
« Reply #187 on: October 01, 2017, 10:15:33 am »
The Pomona 3770 is a nice multiway post at not crazy money, gold plating over tellurium copper, pure copper is almost unmachinable and soft I believe.
Au Mouser http://au.mouser.com/ProductDetail/Pomona-Electronics/3770-0/?qs=yih5jomMvb3Uhbdu3XO%2FAg%3D%3D
Data Sheet http://www.mouser.com/ds/2/159/d3750_60_70_1_01-34263.pdf
Whoah! Watch where that landed we might need it later.
 

Offline branadic

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Re: DIY Low EMF cable and connectors
« Reply #188 on: October 01, 2017, 11:04:38 am »
I do know the Hirschmann gold plated brass things (have them on my desk) and I do know the Pomona multiway posts (have them on my desk too), but for some optical design reasons they are not the perfect choise, but I do want the gold over copper configuration for low noise and low thermal emf. So that's is why I asked if someone knows where to get the Keithley or Prema single banana socket jacks. The Agilent banana block is nothing I can use in my application.

-branadic-
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Offline ManateeMafia

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Re: DIY Low EMF cable and connectors
« Reply #189 on: October 01, 2017, 12:33:22 pm »
Has anyone tested the Keithley jacks to see if they are gold plated copper? They could be brass and depend on the internal meter temp to keep thermals balanced.
The only way I know of to get them is to order a replacement front panel. It isn't cheap but if you have a Keithley meter needing a shiny front cover, you would just recover the old ones.

In the end, the Low Thermal binding posts would be cheaper but still not what you want. The Low Thermal posts are ~$25US/ea and much better quality than the Pomona 3770.
 

Online Echo88

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Re: DIY Low EMF cable and connectors
« Reply #190 on: January 07, 2018, 04:39:12 pm »
I see there are many copper binding posts and spade lugs here listed, but are there any known gold plated copper binding posts available which are cheaper than the Pomona 3770 / where to get gold plated copper spade lugs? I dont like to use non-plated lugs/posts because of the oxidation hassle and for my reference-voltage-switch its not necessary.

Maybe someone has a Data Proof-scanner binding-post-backside which he wants to sell?  :-DD
 

Offline ManateeMafia

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Re: DIY Low EMF cable and connectors
« Reply #191 on: January 07, 2018, 05:16:51 pm »
The 3770 is as low cost as I have found. Mueller makes them with a similar part number but the reported quality is not the same as Pomona.

On my reference array, I use bare copper and I would suspect others here do the same. Sometimes you can't get away from bare copper if you are measuring in the nV range.
Also, my Data Proof scanner is the model with wires and not binding posts so there is only the end at the reference that needs to be terminated. The cable is simple unshielded phone cable.
 

Online Echo88

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Re: DIY Low EMF cable and connectors
« Reply #192 on: January 09, 2018, 02:29:18 pm »
You are right, the necessary costs for a 16-channel 4-wire binding post-scanner are not justifiable. Therefore i will also use wires. But if im using solid-core-wire: does it tarnish after some time even under the clamped binding-post section and accordingly begins to produce high thermal emf-voltage?
 

Offline dl1640

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Re: DIY Low EMF cable and connectors
« Reply #193 on: January 19, 2018, 03:59:45 am »
Remember that noise can be coming in to your DUT on that sometimes dirty power mains ground, so pay attention to how you use / or don't use that - and use a clean quiet dedicated lab "ground" reference as required.   Keep your test leads twisted and short - and remember that the moment you connect those leads to your circuit then your instrument and all the ground loops in between now become part of the whole system measured noise.

i did see our Wavetek 1271 give unstable reading once it was plugged into a power strip with a "dirty" ground.
the cause was the power strip itself didn't has a good ground receptcle, spring is not holding the ground pin of the power cord, tightly.
it was not thermo emf which cause such instability.

i suppose the ground of the mains is going to the breaker panel,
and the dedicated lab ground should be going to the earth directly.

however i feel it very difficult to ensure which ground is more effective.
as many hi-end instrument like 3458 and 5700 has a optional grounding post just nearby the power inlet,
is it a good idea to connect a gound wire from this grounding post to the lab ground (earth) and also the mains ground is connected to the instrument's power inlet?

make sense?

sorry this is off this thread subject in a way.
i'd like to hear some advice and learn something.

thanks!
 

Offline Neomys Sapiens

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Re: DIY Low EMF cable and connectors
« Reply #194 on: January 19, 2018, 04:06:50 pm »
Remember that noise can be coming in to your DUT on that sometimes dirty power mains ground, so pay attention to how you use / or don't use that - and use a clean quiet dedicated lab "ground" reference as required.   Keep your test leads twisted and short - and remember that the moment you connect those leads to your circuit then your instrument and all the ground loops in between now become part of the whole system measured noise.

i did see our Wavetek 1271 give unstable reading once it was plugged into a power strip with a "dirty" ground.
the cause was the power strip itself didn't has a good ground receptcle, spring is not holding the ground pin of the power cord, tightly.
it was not thermo emf which cause such instability.

i suppose the ground of the mains is going to the breaker panel,
and the dedicated lab ground should be going to the earth directly.

however i feel it very difficult to ensure which ground is more effective.
as many hi-end instrument like 3458 and 5700 has a optional grounding post just nearby the power inlet,
is it a good idea to connect a gound wire from this grounding post to the lab ground (earth) and also the mains ground is connected to the instrument's power inlet?

make sense?

sorry this is off this thread subject in a way.
i'd like to hear some advice and learn something.

thanks!
In most parts of the world it is mandatory to connect the grounding conductors together in a controlled fashion (equipotential bonding). Having your electrical supply in your lab grounded locally only would be definitely detrimental to safety. It is viable only for the operational (RF) grounding of antennas, but even there a connection to the ground system (via a spark gap or without, depending on electrical codes) is necessary. Of course, you can improve the grounding for a lab by having a better earth system, but this means setting up a local grounding rail, where you connect them again. To keep out RF via ground, use a ground choke.
 

Offline MisterDiodes

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Re: DIY Low EMF cable and connectors
« Reply #195 on: January 19, 2018, 06:46:09 pm »
Of course a quiet "local" lab ground that is not run in the mains conduits is superior even down to DC - but that doesn't mean it's not safety bonded to the utility company power source -outside- the lab. Keep it safe.

A ground choke and good noise cancling toird transformers will certainly help quite a bit but at low frequencies we've always seen additional noise improvement using a dedicated lab ground, generally using a very wide bandwidth braided cable (lightning rod #1 down-lead in safety shield) leading to a good outside heavy ground connection.  Now the lab has a pristine, un-shared, safe and unpolluted connection to Mother Earth.

The new lab buildings are even spec'd that way from the ground up (pardon the pun) and meets all building code requirements.

The whole point is to keep power mains induced ground currents and Voffsets out of the equipment under test - and if there's any question look carefully and the induced currents that are generated on the ground conductor in a typical mains power conduit entering the lab, at low freq.  The problem is worse if you have heavy equipment on your side of the building's utility co. transformer.

The required (for us) steel mains conduit itself becomes a random 1 turn coupling transformer into the utility ground...You'd think that the random twisting of the mains conductors would reduce the effect - and it does to some extent - but by the same token it doesn't -perfectly- cancel out, because the wires are never twisted perfectly in a balanced fashion.

You get an even greater coupling effect if the mains power cables are strapped to a steel girder or building support - and at heavier current flows you'll see more junk noise cosstalked into the utility ground wire.

In other words:  Watch your mains wiring and see we're you've got accidental built-in UN-balanced coupling transformers - then you see why a dedicated lab ground helps keep measurement noise lower.
 
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Offline dl1640

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Re: DIY Low EMF cable and connectors
« Reply #196 on: January 20, 2018, 08:04:15 am »
hi neomys and mr.diodes

of course most instruments are plugged into 3-prong mains outlet (with ground), and instrument manufacturer require to do so, this is for human safety. after a brief search there are several national codes talking about electical system grounding and i will study them.

our lab very small, just one room. but it do have seperate ground facility apart from mains ground. this lab ground is running of a copper bar around the room, at first the purpose of this facility is to discharge electro-statics through a hand strip.
the problem is i cannot tell if this lab ground is better than the mains ground. if a instrument is connected to both ground, would that be another ground loop?
 

Offline MisterDiodes

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Re: DIY Low EMF cable and connectors
« Reply #197 on: January 20, 2018, 06:49:14 pm »
No, don't use multiple ground points.

What you want to look at is study the isolated ground / dedicated ground techniques used in every modern hospital, serious R&D labs near wafer fabs, and anywhere high precision measurements are done, and you need to keep your measures low noise even though there might be heavy, noisy current flows on the building power mains cables.

Think of the "IG" (Isolated Ground) or DG" setup (dedicated ground which is similar except uses a relatively large ground conductor compared to what is normally called for)  as a Star Ground connection system where you have a very good single ground connection to Earth, and that is a common Earth bond point between your lab, utility power source and mains distribution protection system.  When I say a "dedicated lab ground" that is essence a larger, very low impedance cable leading from your test area back to the very good common bonded ground point outside of the lab room - for instance where you have -multiple- ground rods installed for the mains power system entering the building.

The concept here is that for sensitive equipment you're NOT using the relatively high impedance, noise-coupled copper wire that runs along side the mains cables to make your ground connection - with a DG you're using a good heavy conductor that takes it's own low noise path to the COMMON very low resistance ground point....and you DON'T want to run that ground DG cable along side the normal high-noise mains wiring.

You can still have a common ground bus bar on the test bench like you have but that would be connected to your isolated / dedicated ground conductor (ALONG WITH YOUR "IG" rated equipment sockets) - which is the good heavy conductor that does NOT run along side the power cables.  You are still safely connecting back to the bonded utility ground point - just in a low-noise way.

On some systems where shielded isolation transformers are used, the transformer primary section uses the standard utility ground wire on the power plug, but the inter-winding shield and secondary side uses the isolated & dedicated low impedance ground system.

Generally (as required by law for certain commercial buildings) there is also a grounds circuit monitor system in place that will instantly trip off the mains power (or sound an alarm) in case a safety grounding system goes open for some reason.

You never want to create a "floating" ground situation - that is where you have a ground system that is completely disconnected from the utility / power source ground.  That creates a situation where if you have an equipment failure where a utility mains "hot" circuit can energize the outer cabinet of a piece of equipment - and the mains circuit breaker or GFCI never trips...that's bad.  Don't ever let that happen.  You always need to look at your setup and guarantee that the basic testing setup poses no danger to the equipment operator.  If there is a human contact hazard by the nature of the setup, then that situation needs to be clearly labeled, and perhaps lockouts, safety interlock switches on cabinets and/ or requirement that Personal Protection Gear be worn. At least here in the States that is usually a strict issue with insurance companies and the annual fire / safety code inspectors.

It just depends on the safety / grounding situation and what voltage / energy levels you're looking at.  Usually we never even think about this when testing low voltage, low power circuits < 50VDC - but when you start taking precision measurements at higher voltages - it doesn't take more than one hard accidental "bite" to realize you need to keep your grounding system safe and low-noise.

EDIT:  In the final analysis:  Your most sensitive gear on the lab bench would either get power from isolation transformer or plug directly into IG type mains sockets, and those IG's are grounded to your heavy bench ground bus bar and low impedance DG cable, which in turn runs back to the common utility-bonded grounding point.   That makes everything on your test bench sitting at -one- single common reference point. 

Your lab lighting loads, outlet boxes, conduits and mains raceways, motors etc. would still be grounded the standard way.

NOTE:  You will see some info on the 'net talking about how "IG" systems sometimes don't work well, usually written by non-metrologists who don't normally measure down in low ppm - but the difference here is that on high performance systems you're using a very high performance, heavy grounding conductors - not the piddly little noisy mains wire electricians refer to as the "ground wire".  If you're chasing ppm,  you want a test bench system ground setup that has much lower noise & impedance ground than you'd find in a typical wiring setup.


 
« Last Edit: January 20, 2018, 10:45:19 pm by MisterDiodes »
 

Offline dl1640

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Re: DIY Low EMF cable and connectors
« Reply #198 on: January 21, 2018, 03:12:34 am »
Thank you Mr Diodes for giving so much.
I need some time to study your comments and our real situation.
An 17025 auditor once insisted that our 5700A calibrator MUST be grounded at both mains ground and Earth (rear binding post mounted on chassis) which very much frustrate me. I quote what he said “Your mains ground is going a long way to utility company’s transformer there is attenuation along that way.” Today I suppose he means the mains ground might be dirty. And we have no record/document to prove either mains ground or our lab ground (copper bar) is effective, because the time we moved in this building everything was set up as is, we don’t know how is the exact electrical grounding system work or if it is working properly, difficult to test or verify.

I’d like to keep some questions for next reply to this topic. Thanks  :)
 

Offline MisterDiodes

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Re: DIY Low EMF cable and connectors
« Reply #199 on: January 21, 2018, 06:47:15 pm »
Yes, using two ground points like that is just asking for trouble.  You also need to watch out for current flows across two connected (but different) ground systems - especially corrosion effects you weren't planning on.

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.

The "gotcha!" to watch out for of course is to not have anything like shielded comm's cable shields  (with cable shield connected at both ends) running from that isolated room to any other room in the building... In general you don't want an accidental connection across grounding systems.

Whatever you do - make sure the grounding system is completely safe, quiet, and all the breakers / GFCI work as intended.




 
« Last Edit: January 21, 2018, 07:30:08 pm by MisterDiodes »
 


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