Problems with BNC and chassis termination

[qwerty257]

Hi All,

forgive me if this is the wrong forum but i assume someone here from a test and measurement background will be able to help.

I am trying to measure leakage current using a source meter and electrometer. The problem i have is that the termination method of my instruments is BNC. The DUT i am measuring is inside a shielded diecast box. In order to make my measurement i am using the chassis and the outer core of the coax cable as the reutn path. However i do not know if this will increase noise within the measurement. I am measuring currents in the Nanoamp region.

Also from a safety point of view i am using high voltage and having the return path going through the diecast box does not sit well with me.

Does anyone have any opinions on this or can advise on a better solution?

Thank You

Andy

Here is a diagram of what i am doing

https://forums.tm.agilent.com/community/download/file.php?id=8518&mode=view: https://forums.tm.agilent.com/community/download/file.php?id=8518&mode=view

[Jason_D]

qwerty257,

Are you using any National Instruments hardware that you think might be causing some problems here?

Have you tried the setup you described?  Does it give you the desired results?

[qwerty257]

Yes i have tried this setup and i do get measurments in approximate range. The trouble is its a leakage current test in the Nanoamp range, ideally the leakage should be as small as possible but i am concerned that the config/setup is causing or adding an error to the  reading.

Also i have concerns over the safet of the setup. The only NI product i am using is labview 8.5 to control the instruments but this post is not really a software issue.

Thanks