Author Topic: Triaxial test cables for HP 4140B pA meter?  (Read 382 times)

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Online TERRA Operative

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Triaxial test cables for HP 4140B pA meter?
« on: May 07, 2019, 07:46:58 am »
I recently got my hands on a HP 4140B pA (pico amp) meter and DC voltage source for a good price. I figured it'd be something fun to play with. :)

It looks like the pA input uses a triaxial connector, of which I have nothing in my stock of parts.
I found this on Digikey, but it's not the cheapest test lead out there (I know triax is expensive...)
https://www.digikey.com/product-detail/en/pomona-electronics/5342/501-1407-ND/737265

Does anyone have any suggestions on what sort of test lead I should even be looking at? Also, does 50ohm/75ohm matter here?
« Last Edit: May 07, 2019, 12:51:08 pm by TERRA Operative »
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Offline HighVoltage

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Re: Triaxial test cables for HP 4140B pA meter?
« Reply #1 on: May 08, 2019, 07:34:56 am »
The keyword to search on the used market is "trompeter" and "triax".
Sometimes you can get lucky to find good cables and connectors for a good price.

The price on Digikey is not too bad.
I have seen much higher prices for name branded cables.
There are 3 kinds of people in this world, those who can count and those who can not.
 
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Online VK5RC

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Re: Triaxial test cables for HP 4140B pA meter?
« Reply #2 on: May 08, 2019, 09:39:11 am »
+ search for the term TRB connector, the cable is relatively cheap but the connectors crazy, watch out for 2 (older) and 3 lug versions. If you make your own - remember the impedance needs to be in terraohms - no touch!
Whoah! Watch where that landed we might need it later.
 
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Online TERRA Operative

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Re: Triaxial test cables for HP 4140B pA meter?
« Reply #3 on: May 08, 2019, 10:23:50 am »
Cool, thanks for the info, I'll keep having a look around here and there.

I have the 3 lug type on my machine, they seem common enough.
I'll also be sure to not touch stuff, maybe I'll wear gloves if I assemble my own cable. Would a wipe down in 99.9% Isopropyl alcohol be alright if needed?
Any circuit design must contain at least one part which is obsolete, two parts which are unobtainable, and three parts which are still under development.

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Online VK5RC

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Re: Triaxial test cables for HP 4140B pA meter?
« Reply #4 on: May 13, 2019, 12:05:42 pm »
I made two  2 to 3 lug adapter cables - to join my Keithley Electrometers  (617 619)  to a HP Test Fixture Set  (16058A).
I used the no touch technique - but had washed my hands in IPA first - and the resistance between the layers of triax was not measurable - so I was happy.
Those are expensive connectors!
Hope it goes well.
Rob
Whoah! Watch where that landed we might need it later.
 


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