Model 6517B Electrometer Reference Manual
Section 5: Measurement options
6517B-901-01 Rev. C / August 2015
5-13
Shielded fixture construction
Since shielding is so critical for proper operation of external feedback, it is recommended that a
shielded fixture similar to the one shown in the figure below be used to house the feedback element.
The fixture is constructed of a commercially available shielded fixture modified with the standard BNC
connectors replaced with triaxial female connectors. For convenience, a banana jack can be mounted
on the box to make the necessary PREAMP OUT connection.
Alternately, a wire could be run through a rubber grommet mounted in a hole in the side of the box.
Note that input low is connected to chassis ground within the shielded box. This connection can be
made by using a small solder lug secured with a screw.
Figure 62: Shielded fixture construction
Figure 63: Shielded fixture construction - equivalent circuit
Parts list
Item
Description
MFR part number
1
Shielded fixture
Pomona #2390
2 Female
triaxial
Keithley
7078-TRX-TBC
3
Banana jack
Keithley BI-9-2
4 Triaxial
cable
Keithley
237-ALG-2
5 Triaxial
cable
Keithley
7078-TRX-3