Author Topic: 10k precision resistor project  (Read 6065 times)

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Offline zhtoor

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Re: 10k precision resistor project
« Reply #50 on: March 06, 2018, 12:12:47 pm »
I thought about buying some VAR resistors, and dipping them into molten PCTFE (aka: "Kel-F")-- this material absorbs and/or adsorbs ZERO water vapor-- this is the only alternative I have found to a glass/Kovar hermetic package.  This idea needs testing though...  ::)

hello,

how about parylene coating?

regards.

-zia
 

Offline TiN

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Re: 10k precision resistor project
« Reply #51 on: March 09, 2018, 05:02:19 am »
Thank you, Inverted18650! Got my set of neat Caddock resistors to try for stability. Got them started now to add into my temperature coefficient measurement database,



These will take someo 60-120 hours of my four 8.5-digit DMMs to get all data collected.
And as good excuse, I also got myself new PTFE silver-plated copper kelvin cable to build some fixtures.
This is nice cable, fully shielded and robust to use. I'll be making multiple variants, using both Pomona 5406, Pomona 4892 banana jacks (which have BeCu spring contacts) for poor meters like Keithley 2002 and Advantest R6581T. Best performance cables will also have bare-copper spade lugs for proper connections on devices like Keysight 3458A



Each cable is Kelvin-connected, with four separate conductors to utilize highest precision of the benchtop meters.
 I also want to try alternative idea with reverse-connected spade lug as thermal anchor for DUT-resistor mount.



Code: [Select]
-==================================================================================================¬
¦  xDevs.com TEC Experiment kit        -i- Datafile teckit_caddock_test1.csv exists                ¦
+--------------------------------------------------------------------------------------------------+
¦    GPIB[25] : Keithley 2510                                                                      ¦
¦    GPIB[ 2] : Keysight 3458A                                                                     ¦
¦    GPIB[ 6] : Keithley 2002                                                                      ¦
¦    GPIB[ 3] : Keysight 3458A                                                                     ¦
¦==================================================================================================¦
¦ Sample       :      169               Meter mode   : OHMFO            Set Temp     :  20.000 °C  ¦
¦ Next temp    : 20.000 °C              Measured val : 999.97864710     Process Temp :  19.997 °C  ¦
¦ Min temp     : 20.000 °C              OCOMP/DELAY  : 1, 0 sec         TEC Current  :  -0.3215 A  ¦
¦ Peak temp    : 50.000 °C              Fixed range  : Configure        Status       :  Hold start ¦
¦ Remaining    :  8h 25m 38s            NPLC         :  100.0000        Gain         :  140.0000   ¦
¦ Elapsed time :  0h 12m 09s            Terminals    :   FRONT          Intergal     :    0.1000   ¦
¦ Progress     :    2.35%               REL Value    :      1E-06       Derivative   :    0.9000   ¦
¦                                                                                                  ¦
¦  [   154] : S = 20.000 P = 19.998 I = -0.325 A  VAL = 999.9787099 R, PCB_T = 9004.961776 R       ¦
¦  [   155] : S = 20.000 P = 19.998 I = -0.325 A  VAL = 999.9786758 R, PCB_T = 9004.962009 R       ¦
¦  [   156] : S = 20.000 P = 19.998 I = -0.325 A  VAL = 999.9786614 R, PCB_T = 9004.961039 R       ¦
¦  [   157] : S = 20.000 P = 19.998 I = -0.324 A  VAL = 999.9788573 R, PCB_T = 9004.960913 R       ¦
¦  [   158] : S = 20.000 P = 19.998 I = -0.325 A  VAL = 999.9787782 R, PCB_T = 9004.962207 R       ¦
¦  [   159] : S = 20.000 P = 19.998 I = -0.324 A  VAL = 999.9788177 R, PCB_T = 9004.962189 R       ¦
¦  [   160] : S = 20.000 P = 19.998 I = -0.325 A  VAL = 999.9787513 R, PCB_T = 9004.962279 R       ¦
L=========================================    -21.623==============================================-

Will see soon.


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Offline cellularmitosis

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Re: 10k precision resistor project
« Reply #52 on: March 09, 2018, 05:42:16 am »
Nice setup TiN  :-+.  Where did you get those bare copper spade connectors?  I had to make my own using acid... what a pain!  http://www.eevblog.com/forum/metrology/diy-low-emf-cable-and-connectors/msg1305061/#msg1305061
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Offline SirAlucard

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Re: 10k precision resistor project
« Reply #53 on: March 09, 2018, 08:44:54 am »
Nice setup TiN  :-+.  Where did you get those bare copper spade connectors?  I had to make my own using acid... what a pain!  http://www.eevblog.com/forum/metrology/diy-low-emf-cable-and-connectors/msg1305061/#msg1305061

Bare copper is nice and all, but what do you end up doing to keep them from oxidizing? Dunno if I'd be able to use them all by the time they turned.
 

Offline cellularmitosis

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Re: 10k precision resistor project
« Reply #54 on: March 09, 2018, 10:37:40 am »
I know we are getting a bit off-topic here, but I do wonder if there is a counter-balancing effect -- if the thermal conductivity of the copper is so great that even a thin layer of oxide doesn't matter, because the two chunks of (oxidized) copper are held much closer to thermal equilibrium.

Then again, perhaps copper oxide is a thermal insulator?  Also, the thermal EMF of copper oxide is a killer (something like 4000uV/C?). 

I also wonder what is meant by "copper oxide" when quoting that gigantic thermal EMF figure.  Are we talking about the slightly dull look on copper which has sat out for a few days?  Or are we talking about the green statue of liberty?
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Offline hwj-d

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Re: 10k precision resistor project
« Reply #55 on: March 09, 2018, 11:36:05 am »
(Should i post it?)  :)

OT:

use Coke!

No joke, i use it for my motorbikes alloy wheels and spokes, old chromium car bumpers, and other valuable scrap metal stuff. For that i always have a coke spraybottle and a rag with me.  ;D

But hold on, what the heck does my sister doing there in YT...  :-DD

 ;)
« Last Edit: March 09, 2018, 11:37:40 am by hwj-d »
 

Offline Inverted18650

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Re: 10k precision resistor project
« Reply #56 on: March 09, 2018, 12:15:36 pm »
Its hard to rationalize the silver plate, and then gold plate but I see how it important it is for this level of accuracy. I just ordered some kaowool to improve my mini-foundry and want to experiment with pouring my own pure copper spades as well. I do have some old scrap gold I could try, but truthfully, not only would I literally be throwing away gold, but if I went that far, I would have to go and spend another $500 on cables. I am not sure I can justify it. Stoked to see the results and thank you for all the hard work.
 

Online Vgkid

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Re: 10k precision resistor project
« Reply #57 on: March 09, 2018, 02:16:02 pm »
You guys know you can buy copper spade lugs , right. :o
https://www.omega.com/googlebase/product.html?pn=SLCP-20
Slcp-20 is what you need. 8)
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Offline SirAlucard

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Re: 10k precision resistor project
« Reply #58 on: March 10, 2018, 05:55:47 pm »
I also wonder what is meant by "copper oxide" when quoting that gigantic thermal EMF figure.  Are we talking about the slightly dull look on copper which has sat out for a few days?  Or are we talking about the green statue of liberty?

I don't think we'd be able to get it to a green oxide like the statue of liberty. However definitely the darker dull copper look. I mean imagine it would actually insulate the copper a bit. Since it's forming a layer on top of the copper.
 

Offline MasterTech

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Re: 10k precision resistor project
« Reply #59 on: March 17, 2018, 11:33:25 pm »
To give shape to the copper enclosure I took a plastic rod and milled it to have a planar face and two longitudinal groovings




After that I inserted in the bottom side of the enclosure a PCB with a conductive mesh soldered to it, this separates the heater from the resistor itself



After putting all in place, filling with oil at 45º and sealing the fill gap, this is the result. All the feedthroughs in the upper side are Tusonix 2461-001-X7V0-102PLF



I also took 4 golden binding post from a broken advantest R8340A I have, they are thicker than pomona 3770, so 40€ saved there.



Now I'll have to build container box, temp control, etc...
« Last Edit: March 17, 2018, 11:39:15 pm by MasterTech »
 
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Offline TiN

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Re: 10k precision resistor project
« Reply #60 on: March 18, 2018, 07:58:55 am »
Nice SFRS (Smiley face resistance standard)  :-+.
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Offline quarks

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Re: 10k precision resistor project
« Reply #61 on: March 19, 2018, 05:25:47 am »
your binding posts look very much like BP-1000 which are available from IET (see att.)
« Last Edit: March 19, 2018, 05:30:34 am by quarks »
 

Offline Inverted18650

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Re: 10k precision resistor project
« Reply #62 on: March 19, 2018, 10:51:24 am »
MasterTech: this is great. Thank you for posting.
 

Offline Conrad Hoffman

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Re: 10k precision resistor project
« Reply #63 on: March 19, 2018, 02:00:52 pm »
$69 for a binding post? Each? Seriously?
 

Offline TiN

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Re: 10k precision resistor project
« Reply #64 on: March 19, 2018, 03:11:45 pm »
Yea, I'll go with Low Thermal ones for 36% of that cost. They also look much nicer than these.  :-/O
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Offline MasterTech

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Re: 10k precision resistor project
« Reply #65 on: March 19, 2018, 06:49:20 pm »
your binding posts look very much like BP-1000 which are available from IET (see att.)

Based on dimensions it seems so. The pomona 3770 look like a kids toy compared to these sturdy ones.

Quote
MasterTech: this is great. Thank you for posting.

Thanks. There are a couple of details when building hermetic oil cans like these. Specially the thermal expansion coefficient of oil is not negligible. That's why I made that planar face with groovings, and thats why it was filled with warm oil, I prefer it to shrink when it is cool rather than expand when heated
 
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Online eurofox

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Re: 10k precision resistor project
« Reply #66 on: March 19, 2018, 07:01:39 pm »
Yea, I'll go with Low Thermal ones for 36% of that cost. They also look much nicer than these.  :-/O

Where do you get those "cuties"?  :-DD
eurofox
 

Offline SirAlucard

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Re: 10k precision resistor project
« Reply #67 on: March 20, 2018, 02:23:13 am »
$69 for a binding post? Each? Seriously?

I was thinking the exact same thing.. >.< I mean I guess they're gold plated so ehhh? I wouldn't really want to pay that much regardless for some bindings.
 

Offline Edwin G. Pettis

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Re: 10k precision resistor project
« Reply #68 on: March 20, 2018, 03:56:27 am »
ESI/IET binding posts have always been over priced, nothing exceptional except the cost.  I've seen the BOM pricing on things like a SR1 transfer standard, if you bought all of the parts separately it would cost much more than what they charge for the SR1. 
 

Offline qihe_kim

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Re: 10k precision resistor project
« Reply #69 on: March 27, 2018, 06:26:32 pm »
This new design is pretty good .
 

Offline HighVoltage

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Re: 10k precision resistor project
« Reply #70 on: March 27, 2018, 08:38:45 pm »
$69 for a binding post? Each? Seriously?
And I thought that $20 for a LowThermal binding post was a lot.

Nice thread here, thanks.
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Offline MasterTech

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Re: 10k precision resistor project
« Reply #71 on: March 27, 2018, 09:00:45 pm »
This new design is pretty good .

Thanks, I didn't bother to do a Solidworks 3d mechanical design but I quickly did this more or less hand drawn cutaway view.

Done with ipad pro+apple pencil for those apple fans :)
 
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