Electronics > Metrology

My TRIAX cable shielded box project for Keithley Instruments

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HighVoltage:
Project 1
This is my first attempt to build a shielded box with a TRIAX Cable to measure very high resistance values with my Keithley 614 Electrometer. This meter has the dual pin TRIAX connector and I found a fitting cable.

These are the highlights of the materials used:

- Metal box with metal lid
- Bottom and side of the box covered with 5 mm thick PTFE (Teflon) plates
- Original Keithley TRIAX cable
- Outside shielding connected to the metal box (blue cable)
- Inside shielding extended with copper/silver-plated cable and Teflon insulation (orange cable),  (crimped)
- Inner core extended with copper/silver-plated cable and Teflon insulation (orange cable),  (crimped)
- Crocodile clips pure copper (crimped)

This Russian military glass resistor inside the box is marked with 100 GOhm and reads very stable 95.5 GOhm after a few minutes of not touching anything. So far I am happy with this box for this older Keithley 614 Electrometer.

OK, I am looking for improvements and hints of what to change or do differently for the next project.

My next box will be for the DMM7510 and 2450 SMU (3 pin TRIAX)
One improvement I would probably use are Triax Panel Mount Connectors.
But they are sooo expensive, same as withe the TRIAX cables.
 
Thanks for any suggestions.

VintageNut:
Remove the resistor from the box. Leave the alligator clips where they were. Close the box. Force maximum voltage and measure current. This will tell you if you have any leakage.

plesa:
Fisher make triax which are cheaper than BNC ones. Or SHV or MHV ( high voltage BNC) are another option.
White panels are from PTFE?
If you want to make experiments with photodiodes I propose to put some black paper to panels.
And add temperature and humidity measurement.
If you are going to make some HV experiments add protection to your electrometer (GDT, 1M-100k resistors and two antiparalell diodes 1N3595 or DPAD1 are good).

manganin:

--- Quote from: HighVoltage on December 03, 2016, 04:23:32 pm ---OK, I am looking for improvements and hints of what to change or do differently for the next project.

--- End quote ---

I did something similar last year.

A cheap cash box (from Lidl) with a row of BNC feedthroughs (one triax) and a flexible copper strap connecting the top and the bottom.

Two of the connectors with fixed crocodile clips for measuring resistors. No wires or components touching the box = no leakage path.

quarks:
very interesting, thanks for sharing

I just saw this Video

in there I saw Agilent box (around 4:06min it is large in the frame)

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