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6430 + 6517B Differential 4Probe Measurement

Models 2400, 2401, 2410, 2420, 2425, 2430, 2440, 6430
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JCP2017
Posts: 2
Joined: May 30th, 2017, 3:15 pm
Country: United States

6430 + 6517B Differential 4Probe Measurement

Post by JCP2017 » November 2nd, 2017, 1:14 pm

Hi,

I am constructing a high resistance four-point probe measurement system using the 6430 + preamp as a current source and two 6517B's as guarded voltmeters. The DUT is inside a vacuum chamber with triaxial feedthroughs (see attached figure). According to Keithley application note number 2615 and best grounding practices, the 4th probe should be connected to the low of all 3 instruments and then only one instrument's LO terminal is connected to ground. However, the outer shield of the 6517B is chassis ground and the outer shield of the 6430 is IN/OUT LO. Therefore, LO is connected to two different chassis grounds at the vacuum chamber and the LOs of the 6517B would be connected to another chassis ground in the back of one of the instruments.
Differential 4probe.jpg
Differential 4probe.jpg (312.78 KiB) Viewed 4036 times
Will this create a ground loop problem? Should I use adapters that disconnect the triaxial chassis grounds of the 6517B's from the sample chamber?

Thanks in advance

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