Author Topic: My TRIAX cable shielded box project for Keithley Instruments  (Read 44258 times)

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Offline Brad O

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #75 on: August 01, 2018, 09:14:40 pm »
For the Keithley cables, 7078-TRX is the name of the cable itself, the 3rd number is the length designation as you probably guessed.  7072 is a switch card that uses 7078-TRX cables, so some of HighVoltage's cables must've originally accompanied that card.  Besides a few special exceptions, all Keithley instruments that use triax will use this cable, the cable design goes back almost as far as triax itself.

The connectors on the 7078-TRX cables have their own part numbers and can vary, usually it's a CS-631 3-slot male connector.  Here's the closest thing to a datasheet I could easily find, it has and a few specs and an interesting blow-up diagram of the connector: https://www.tek.com/manual/model-cs-631-3-lug-cable-mount-triax-connector-users-guide-manual.  I'm not sure of the details on the 2-lug versions of 7078-TRX cables, but I can search around here more if anyone wants.

The female connector for the CS-631 has the part number CS-630 and has two different bulkhead connector styles, 237-TRX-TBC (usually for high voltage applications, the other side is a coax cable mount) and 7078-TRX-TBC (The more common one for fixtures with ready to solder pins on the other side).  As I just learned, TBC stands for Triax Bulkhead Connector, just a fun bit of trivia for ya.

Not as helpful in terms of specs, but this doc has descriptions, pictures, and part numbers for all the Keithley connectors I mentioned: https://www.tek.com/datasheet/connectors-adapters-and-tools/connectors-adapters-and-tools
 
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Offline HighVoltageTopic starter

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #76 on: August 02, 2018, 12:00:38 pm »

I'm not sure of the details on the 2-lug versions of 7078-TRX cables, but I can search around here more if anyone wants.

Brad O
Thank you, for the very good information...
And yes, if you find any info on the older 2-lug versions, please share them with us.
I still have a few older Keithley instruments with 2-lug terminals.

Since I started with my Triax box, I have tested many different cables
and came to the conclusion, that the original Keithley cables are the best so far.
They are metrology grade it seems and worth their price.


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Offline Brad O

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #77 on: August 02, 2018, 03:32:29 pm »
Well here's a whole bunch of part numbers for the 2-lug versions of the Keithley triax cables.  I don't know how much luck you'd have trying to find any of these, but if you can find these parts you could make your own cables.

7024 cables are the 2-slot male triax cables, the 2-slot connector itself has the part number CS-141.  7023 is the product number for the female bulkhead connector, its part number is CS-440.  The model 617 originally came with a 6011 cable that's the same as the 7024 cable but has one end terminating in alligator clips.

The 7024 and 7078 cables both use the same raw cable (I was wrong earlier when I said the 7078 is the name of the cable itself, it's the product number for the 3-slot version).  The raw cable has the part number SC-22.  Here's a datasheet I found on it, sorry it's a direct download link: https://forum.tek.com/download/file.php?id=24731  These cables have graphite insulation to help make them low noise, but they're not the lowest noise triax cable Keithley uses, I *think* that title belongs to the 4200 and 4200A triax cables that use cable with the part number CS-181, they have a tighter weave and are held to closer specs, but they're also only rated to 250V (They're called Ultra Low Noise Triax Cables). 

This might also be helpful to you, the 6172 (P/N CS-500) adapter is used to connect 3-slot triax cables to 2-lug triax connectors, so finding one of those might be cheaper in the long run than buying whole separate cables for your 2-lug triax instruments.  The 6171 (P/N CS-505) adapter goes the other way.

I'm uploading an old catalog of Keithley connectors (circa 2003) and here's an old catalog of cables that gives part numbers on page 3: http://farnell.com//datasheets/1993899.pdf
 
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Offline LapTop006

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #78 on: September 07, 2018, 06:22:16 am »
I'm uploading an old catalog of Keithley connectors (circa 2003) and here's an old catalog of cables that gives part numbers on page 3: http://farnell.com//datasheets/1993899.pdf

I'm tempted to ask for a quote on the invisible USB cable on the last page.
 

Offline HighVoltageTopic starter

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #79 on: September 07, 2018, 08:44:18 am »
My 7078-TRX-5 has arrived. It's fully compatible with MOLEX 73175-0010 and SMU 2450.
Also i increase PTFE shield in my box.
That looks very nice.
How about a safety switch for lid, so the 1000V would not stay life, when the lid is removed?
 
I got the same humidity sensor but have not integrated it in to my box.
Your integration of the sensor looks very nice!
 
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Offline Doege

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #80 on: September 18, 2018, 07:12:45 am »
I am doing a similar setup, and I cannot ID the connector on the instrument. To make it worse I do not even have access to the instrument at this time, only pictures. As the parts are quite expensive, I hope to get the connector IDd by someone knowledgeable. Please have a look at this stack exchange question where I have the pictures: https://electronics.stackexchange.com/questions/396471/unknown-triax-connector

Thank you for your time, and sorry for posting in this thread. It just seemed like I can reach the correct people and this is very recent thread too.
 

Online Berni

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #81 on: September 18, 2018, 07:43:15 am »
Now now THAT is an evil looking connector. To me it looks like a TNC version of triax.

But you can often find some very obscure cables on ebay if you look for long enough (Problem is that they often don't have the right name in the title because the seller has no idea what the cable even is)
 

Offline Brad O

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #82 on: September 18, 2018, 01:55:29 pm »
That's an RF triax cable for high frequencies, wow, you really don't see them very much. 

The female connector on the instrument is P/N 1250-2228, I couldn't find one for just the male connector, looks like Keysight only sells the whole cable.  Here's the service manual for the instrument: http://literature.cdn.keysight.com/litweb/pdf/04339-90043.pdf and the test fixture: https://literature.cdn.keysight.com/litweb/pdf/16117-90041.pdf?id=689310 (I think the male connector is included in P/N 16117-61604, "Cable Assembly (triaxial)")
 
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Offline HighVoltageTopic starter

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #83 on: September 18, 2018, 02:42:32 pm »
I saw one of these connectors on an old HP adapter with lots of cables on ebay.
Good to know, it is a RF Triax connector!
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Offline Doege

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #84 on: September 19, 2018, 07:09:54 am »
That's an RF triax cable for high frequencies, wow, you really don't see them very much. 

The female connector on the instrument is P/N 1250-2228, I couldn't find one for just the male connector, looks like Keysight only sells the whole cable.  Here's the service manual for the instrument: http://literature.cdn.keysight.com/litweb/pdf/04339-90043.pdf and the test fixture: https://literature.cdn.keysight.com/litweb/pdf/16117-90041.pdf?id=689310 (I think the male connector is included in P/N 16117-61604, "Cable Assembly (triaxial)")

Thanks, I have now done search with those part numbers. Since the instrument and accessories for it are discontinued these cable assemblies can only be bought second had.

But you gave me new hope by naming it "RF triax cable for high frequencies". I will search for that as well, before I result in desperate measures and buy a cable assembly. It's a sin to cannibalize already rare item to get the adapter so I'll try to avoid that.

Thanks everyone!
« Last Edit: September 19, 2018, 07:12:21 am by Doege »
 

Offline syau

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #85 on: September 25, 2018, 11:34:35 am »
The Triax BNC connector used in the MIL-STD-1553B may be another option

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com.hk%2Fulk%2Fitm%2F263335577143
 

Offline Doege

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #86 on: October 08, 2018, 06:30:48 am »
The Triax BNC connector used in the MIL-STD-1553B may be another option

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com.hk%2Fulk%2Fitm%2F263335577143

I found this company who makes drop-in replacements for 4339 accessories. https://www.skgautomation.com/agilent-4339b.html
 

Offline HighVoltageTopic starter

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #87 on: October 26, 2018, 10:17:34 am »
Very interesting comparison between the two instruments.
I will repeat your test, to see if I get the same artefacts at 21V and 35.8V

I now have a Keithley 6517B as well and just got all the original connectors
from Tektronix for the back of the instrument.

BTW, you have nice lab pictures on your Instagram account.
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Offline coppercone2

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #88 on: October 28, 2018, 04:39:23 am »
I wonder if you can polish PTFE to have a smoother surface and retain less crap and clean easier. On the other hand its soft and its going to possibly embed the lapping material.

It does look like your box fits together very poorly though. Why did you decide not to square up the edges?

How did you cut the material?

Other suggestions :

Add strain relief to the solder joints.

Don't just wipe the surface. After you wipe it, hold the box upside down and rinse it with methanol from a squirt bottle.

Actually, why even have teflon on the walls?

It would seem like using a bigger piece with the circuit in the middle would work better then the walls because its easier to clean

and I thought you were supposed to use cotton gloves for this to avoid anything coming out of the rubber ones (i.e. put cotton over the latex).
« Last Edit: October 28, 2018, 04:45:53 am by coppercone2 »
 

Offline coppercone2

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #89 on: October 28, 2018, 06:49:27 am »
I don't know if latex uses any kind of additive or has any materials which leach out of it when its stretched. I think they are meant for health purity not electrical purity. 

But for the cleaning I mean, if you put methanol on a wipe, and wipe something down, all you do is dilute it (same if you soak it in a tub). You want to run fresh methanol over the whole thing and throw away the washings so your not just diluting the grease naturally (or not so much) found in air.

Same for prepping stuff for plating etc, you can soak it and wipe it down first to mechanically stir things up and remove the bulk of the contaminate, but you wanna squirt fresh solvent on it and let it drip off for the final clean, then let it air dry. Think of a soxhlet extractor.

Or, when you wash dishes. You don't just soak the dishes in soap water or use a towel on em then put it in the drying rack, you rinse them under running water to make sure all the soap, oil, etc is gone after you scrub them.

https://www.jokertattoo.net/images/H1003-13%20500ml%20new.jpg

Ideally you would want plasma cleaned sapphire I think. Not sure if you can plasma clean teflon.
« Last Edit: October 28, 2018, 06:57:46 am by coppercone2 »
 

Offline coppercone2

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #90 on: October 28, 2018, 07:00:47 am »
you might actually be slightly dissolving the gloves with very pure methanol (its kind of an aggressive solvent). Latex is natural after all. Not sure if you can use a mixture of methanol/super pure water to clean the surface a bit but not attack them to possibly let more stuff out. Not sure if plastic/vinyl/etc are any better because they probably use plasticizes.

Really not sure, you would something like a gas chromatograph to detect such small changes. Might be non issue, but I swear I read some where (maybe keithley) that they recommend clean cotton gloves, perhaps with a specific weave/fiber type.

You are not really worried about particles falling down (since you  can blow them off) but more like oils.


:easy solution:
use ceramic tweezers and ceramic tools which you can heat past 400C for cleaning to remove all oils. Ceramic tweezers are really nice, you can hold them in a direct jet-flame for a while, till the soot burns off.. defiantly no oil or organic molecule left there. When I cleaned some high-z stuff I made, I used high purity diethyl ether for cleaning. High purity methanol might be better but I think its a more aggressive solvent and its also toxic, so I prefer to use ether because it metabolizes into ethanol. I believe methanol is carcinogenic I don't want to breath that crap if I don't have to.
« Last Edit: October 28, 2018, 07:09:44 am by coppercone2 »
 

Offline coppercone2

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #91 on: October 28, 2018, 07:16:17 am »
if you use compressed air to clean it, the way I measured my air or gas purity, at least to get an indicator without complicated things, is to attach your gas flow to a PVC tube so there is significant flow and no back-wash or diffusion, then put one of those e-bay humidity/temperature probes in there (usually meant for HVAC use), then measure the dew point, you can see what standard your air falls into based on the dew point using industrial guides.

You will probably be disappointed by most compressors, so I recommend getting a small nitrogen tank from the welding store. They are used for filling pipes or fuel tanks etc with nitrogen when you are doing brazing or soldering, so you don't get red-hot metal exposed to air making corrosion on the inside. They also sell special adapters for routing the gas into pipe networks. 

The manual says 'nitrogen gas' because they KNOW facilities air is typically garbage. You can also buy clean dry air in a cylinder but the problem is, for nitrogen you can get the small sized tank, some welding suppliers will only sell you the air if you RENT a tank that is as tall as you, because no one wants to buy small tanks of air typically. But plenty of people buy small nitrogen tanks.

Small air tank is still kind of useful though if you have compressed air tools and you need to do a quick job like use a small nail gun inside of the house to fix something etc. Eventually I will buy one.

Big one is even more useful though, because you can properly run a plasma cutter on it. I ran my plasma cutter on nitrogen but without the oxygen content it does not do as good a job cutting regular steel (good for stainless or some shit tho). The little electrodes wear less when you use proper air, rather then the humid compressor shit. It's also fairly quiet compared to a compressor fucking off on you and going BRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR enough to wake the local dead.
« Last Edit: October 28, 2018, 07:22:14 am by coppercone2 »
 

Offline HighVoltageTopic starter

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #92 on: October 29, 2018, 08:19:14 am »
I totally agree,

For anything metrology gear pressure cleaning, I always use compressed nitrogen from a bottle.

Even if you have an oil and water filter in line with compressed air from an air compressor, it is never clean enough.
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Offline Brad O

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #93 on: October 29, 2018, 05:22:26 pm »
Compare Keysight B2985A VS Keithley 2450 with a tons of low noise triax'es (low current IV plots 50-140 pA)
...
2450 - with artefacts at 21V and 35.8V.
The artifact at 21V is almost certainly due to autoranging, I see another small blip at 2V that would be the same thing.  The blip at ~36V is a little more strange, but it could be something with the interlock.  You may want to check your protection circuit to see if there's any room for a bad connection (especially if the protection circuit is just a wire).

PS. Keithley KickStart 2 looks very simple and useful, i already purchased license. But export from KickStart to csv is little terrible.
Thanks for the feedback, I'll pass this along to the engineers! Could you elaborate a little more on how you want CSV export to work though?  Like is the process to complicated or something else?  You can also reach the desginers directly by emailing kickstart at keithley.com, that address is also listed in the settings window.
 

Online Echo88

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #94 on: November 07, 2018, 10:24:06 am »
I want to test and use a few foil caps (KEMET C4AEhttps://www.mouser.com/ds/2/212/KEM_F3046_C4AE_RADIAL-1107630.pdf, WIMA MKS4 https://www.wima.de/wp-content/uploads/media/d_WIMA_MKS_4.pdf ).
What are the recommended alcohols/solvents to clean the foil-caps to get rid of debris/skin-oil, without affecting the plastic-casing?
 

Offline HighVoltageTopic starter

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #95 on: June 26, 2019, 09:06:36 am »

* If you do not use a power source in B2980 series Electrometer - set 0V output voltage and turn-on output, or disconnect that cable from shielded box. Otherwise that wire emit noise into box.

Great suggestions.

I had noticed this as well and when I don't use the electrometer as a source, I disconnect the cables completely.
So far I had not tried to set the output to 0 and turn the output on.
Good point, I will try that.

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Offline TiN

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #96 on: April 14, 2020, 06:16:24 am »
Strange connection, I'd expect guard to be tied to the enclosure, so leakages and charge from enclusure are isolated from sensitive nodes inside. Guess you did that to avoid building more traditional box in a box construction?
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Offline HighVoltageTopic starter

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #97 on: April 14, 2020, 03:24:44 pm »
How stable are your resistor measurement results ?

I am working on a new shielded box with another shielded box in the box.
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Offline TiN

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #98 on: April 15, 2020, 01:05:06 am »
Reminds my previous failed project 2 years ago.  :D





While it worked somewhat decent up to 10 GOhm higher values (100G, 1T, 4T) were changing output just from thinking about it  :palm:
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Offline KeepItSimpleStupid

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Re: My TRIAX cable shielded box project for Keithley Instruments
« Reply #99 on: April 15, 2020, 11:31:34 am »
i don't see any guard plates.

The outside case should be ground.
Then you need guard.  This generally connects to the inner shield.  It should be driven with the same voltage as the inner conductor.
Now something insulating that doesn't have a lot of capacitance.
Device goes on top of that insulated and guarded plate.

Keithley Triax cables have  layer of graphite to reduce the triboelectric effect.
You have to somewhat watch out for the piezoelectric effect.  i.e. Squishing the Teflon/PTFE.
System should not be subject to vibration.

 


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