Question: I am reaching out to clarify if the ground is necessary for the triaxial cable. It is easier to find adapters and vacuum feedthroughs for BNC cables.
Answer: We typically recommend maintaining ground when adapting from triax to BNC.
We offer a few options that provide this connection to mate to your BNC fixturing:
237-BNC-TRX: 3-Lug Female Triax to Male BNC Connector with guard disconnected
7078-TRX-GND: 3-slot Male Triax to female BNC Adapter (guard removed)
Guard will carry the same potential as the center pin (HI) of the cable. This is used to minimize leakage current through the cable insulation from center pin to ground, providing improved low current measurement accuracy.
This video provides additional information about cabling and guard: https://youtu.be/TBVeXlxNO-U?si=YrfPYo-PyjwW8f71
When adapting to a coaxial (BNC) connection and removing the ground, the guard voltage will be applied to the outer shield of the BNC connector and any associated shielding or grounding within the fixture.
This configuration can pose a safety risk to operators and is generally not recommended.
If you choose to proceed, ensure that the fixture maintains a dedicated safety ground, separate from the cable and instrument, and that the guard is properly connected.
This approach can allow safe implementation while preserving guard functionality through coaxial cabling.
However, I cannot provide assistance with fixture design and strongly recommend using an adapter that removes the guard while maintaining the safety ground.
If you opt for the guard-removed configuration, with ground maintained on the outer shield, adapt as close as possible to the device under test or shielded fixture.
Doing so will help preserve the accuracy benefits of the guard throughout the triaxial cable and minimize any negative impact from converting to BNC.