Electronic – Properly earth grounding benchtop supply

groundinggroundloopspower supply

A DC benchtop supply is usually ground free, i.e. the negative output is floating wrt earth ground. I used to use HP E3630A which has an additional "Earth Ground" pin and to which I shorted the "-" pin.

Now I have a power supply (Keysight E3648A) that has only four outlets: "+", "-" for each "Output 1" and "Output 2". I need +/-5V for testing a PCB so I put them into track mode and short "Output 1 -" with "Output 2 +", calling this "ground".

This "ground" and the supply voltages go to my test PCB which has its grounds (indirectly) connected to other devices over SMA cable shields (signal generators, signal analyzers).

Now I am not sure how to best connect "ground" to earth ground or if I should keep it floating in the first place?

Interestingly the manual does not discuss earth ground at all and how to properly connect it. Any recommendations?

Best Answer

"Ground" is defined as 0V reference and used for measurement purposes.

"Earth ground" is used primarily for safety and bypassing common mode noise currents.

When you want to connect "Earth ground" to your local "ground" then this point becomes your 0V reference. Generally this done at the point of power entry on the board but it may also become connected to coaxial chassis mounted connectors etc.

Just keep in mind any power line filter Y cap to earth ground and/or shield currents to earth ground may influence your local ground.

It is usually OK to connect earth ground at the PS Return by a jumper except when RF is involved. This external low impedance "earth ground" connection may serve to attenuate high impedance stray coupling from sources of EMI.