My TRIAX cable shielded box project for Keithley Instruments

[4CX35000]

It will be slight thermal variations that you are noticing, but probably within the specification of the resistor. Look at the datasheet for thermal characteristics.
I have seen similar variation on my old Keithley 617. In my case it variation was within the limits of the resistor I'm using.

What resistor are you using ?

[HighVoltage]

What resistor are you using ?

I am using a Russian military resistor, like in the following picture.

[HighVoltage]

My Keysight B2987A Electrometer arrived today.
I thought I will do a quick measurement, but it seems the learning curve is a little steeper then expected.
So, I guess it will be a while before I will open the instrument up.

[plesa]

I do not want to bias you. I have same experience. Menu is not too intuitive.

[HighVoltage]

shodan@micron

Nice shielded box you have built.
I got the very same E+E sensor as well, just have not mounted it.

And yes, even after a while of usage, the Keysight B2987A is horrible.
But it can be easily controlled by remote software.

What is it that you want to measure, when you are done?

[Berni]

I just came across this thread and does it sure have some electrometer porn in it.

I had a plan to build a box of my own but never finished it. However i resorted to using XLR on the other end due to triax being so ridiculously expensive. The cables i ended up using for my HP 4041B SMU are actually twinax rather than triax as i could get a bunch of them on the cheap to fill out the 5 channels on that instrument. But that works just as well since the pinout goes: center sense, middle force, outer guard. And yes this means grabbing the outer metal body of the triax can give you a 100V shock.

My Keithley 617 Electrometers had the additional challenge of having the 2 lug triax plug. Has taken me quite a while to find one on ebay for a reasonable price.

But im doing all this on the cheap. You guys probably have cables that cost more than my whole setup.

[plesa]

And yes, even after a while of usage, the Keysight B2987A is horrible.
But it can be easily controlled by remote software.

Unfortunately, I can confirm it

[HighVoltage]

Typically, i want check: leakage HV diodes, capacitors, resistance of PCB, quality of coating for HV circuits. It very important for me, because i make many different HV converters powered by small battery.

In future i have plans for low voltage and low current circuits.

Nice, keep us posted with some pictures, of how it works out.

But im doing all this on the cheap. You guys probably have cables that cost more than my whole setup.

If you look long enough on ebay and other places, good deals can be found.
But in general, these parts are ultra expensive.

Buying full length cables and cut them in half to make some adapters
also safes some money.

And yes, even after a while of usage, the Keysight B2987A is horrible.
But it can be easily controlled by remote software.

Unfortunately, I can confirm it

I think the day will come that I will sell the Keysight B2987A and get a new Keithley 6517B instead.

[plesa]

And yes, even after a while of usage, the Keysight B2987A is horrible.
But it can be easily controlled by remote software.

Unfortunately, I can confirm it

I think the day will come that I will sell the Keysight B2987A and get a new Keithley 6517B instead.
[/quote]

I have on my bench Keysight for 2 weeks or so and it was nightmare and purchased Keithley 6517B for same price. Before selling B2987A you can make teardown

[HighVoltage]

I have on my bench Keysight for 2 weeks or so and it was nightmare and purchased Keithley 6517B for same price. Before selling B2987A you can make teardown

OK, so at least I am not alone, thanks for your confirmation.

The Keysight B2987A on paper specs looks so great but in real life it is so different.
I should have borrowed one before I bought it.
Ok, I will make a teardown of the B2987A before I sell it.

[Zucca]

I had a plan to build a box of my own but never finished it. However i resorted to using XLR on the other end due to triax being so ridiculously expensive. The cables i ended up using for my HP 4041B SMU are actually twinax rather than triax as i could get a bunch of them on the cheap to fill out the 5 channels on that instrument. But that works just as well since the pinout goes: center sense, middle force, outer guard. And yes this means grabbing the outer metal body of the triax can give you a 100V shock.

Sorry for bombing in the thread,
FYI I am selling some decent triax cocaine with a K220:

https://www.eevblog.com/forum/buysellwanted/zucca-sales-(d)-keithley-220/

- Triax Cable Keithley 237-ALG-2
- POMONA 5299 adapter Triax F zu BNC M,
- Triax Cable Keithley 7078-TRX-10.
- Triax Cable grey, I think it is Agilent
- Calibration Fixture as described in the 220 Service Manual page 5-2.

 

[Berni]

Nice collection of stuff you are selling there and even close to me, tho the price is still a bit steep for me given how much I use this stuff.

And yes I did cut triax cables in half to save cost. 5 triax to triax cables and 5 panel mount triax connectors I don't even want to know how much it would cost. Even nice XLRs are cheaper and they work well enough in my experience.

[Zucca]

First rule buy only what you need, don't do like me 

[Echo88]

If we would only buy what we need this forum-section wouldnt exist.   

[HighVoltage]

I am glad to buy more than I need, because eventually I will need it.


Zucca
That is a nice collection of TRIAX cables.
I am surprised it is not sold!

[Berni]

First rule buy only what you need, don't do like me 

Looking at the U42 rack and bench shelve full to the brim with equipment...yeah that's exactly what I was doing 

I would ask for the triax bits seperately if my electrometer didn't have the dreaded 2 lug Triax connector on it.

[plesa]

WOW! I found cheap Triax cable from Pomona:
5223-60 (3 Lug, 1.5m, Belden 9222) - 122$ per pcs.
5223-36 (3 Lug, 0.9m, Belden 9222) - 116$ per pcs.

I will try buy it.

For this price you can have real low noise triax. Belden ones are not low noise.
The used connectors are also not suitable for low current measurements
Check this
https://www.ebay.com/itm/KEITHLEY-7078-TRX-3-3-SLOT-TRIAX-CABLE/273100148716?
https://www.ebay.com/itm/LOW-NOISE-TRIAX-CABLE-7078-TRX-5-for-Keithley-236-237-238/331810119121?

[ch_scr]

shodan@micron, the Keithley Triax is indeed different. I got some surplus Triax connectors from ebay that fit the more conventional "Keysight" Style with ease (i have an old HP Test fixture) - but on my Keithley 2636, they are very hard to push in. Hard enough that it almost feels like damaging it, definitely increased wear. I would really like to know where to get those Keithley-Style connectors to make my own Cables. The connectors that came on my Keithley cable have no part number on it.

[TiN]

These are high-voltage triaxes, common for parametric analyzers (can go up to 2kV).

[HighVoltage]

And the high voltage triax connectors are NOT compatible to the "normal" triax connectors.
And usually they are much more expensive.

[HighVoltage]

PS.I did not expect that Keithley and Keysight are different 3 lug triax's 

The Triax connectors on my Keysight B2987A and my Keithley 2450 are the same.

I finally bought a Keithley 6517B, it should arrive soon.
Then I can do a real comparison between the 6517B and the B2987A and the source meter 2450

[HighVoltage]

I will take some pictures and measurements tomorrow on the instruments I have at hand.

[HighVoltage]

OK, I made some measurements

Keithley 2450 SMU
- Outside: 9.63 mm
- Inside: 8.16 mm
- Inside inner shield: 4.39 mm
- Depth to inner shield: 3.38 mm
- Depth to inner insulator: 4.65 mm

Keysight B2987A
- Outside: 9.50 mm
- Inside: 8.28 mm
- Inside inner shield: 4.28 mm
- Depth to inner shield: 3.46 mm
- Depth to inner insulator: 3.57 mm

CHINCH Trompeter BJ770
- Outside: 9.68 mm
- Inside: 8.25 mm
- Inside inner shield: 4.50 mm
- Depth to inner shield: 3.31 mm
- Depth to inner insulator: 3.24 mm

Keithley T-Connector
- Outside: 9.68 mm
- Inside: 8.30 mm
- Inside inner shield: 4.37 mm
- Depth to inner shield: 3.17 mm
- Depth to inner insulator: 3.37 mm

Y-Adapter TN2A (metrology grade)
- Outside: 9.70 mm
- Inside: 8.22 mm
- Inside inner shield: 4.39 mm
- Depth to inner shield: 2.94 mm
- Depth to inner insulator: 2.91 mm

[HighVoltage]

Of the many original Keithley cables I have,
most of them are marked 7078-TRX-3 but two cables are marked 7072-D

I can not detect a difference in these Keithley cables.
They fit all my Triax connectors well.

[TiN]

marked 7072-D

D stands for dirty.