Attached is the current lab setup for my chip testing. The green square represents the main PCB board, and little blue square represents the chip. The chip needs separate VDD voltage for its analog and digital circuits, but their ground is tied on the green PCB. From here, I am seeking advice regarding the possible concerns about ground loop if '-' terminal of PSU is connected to the earth ground in the given situation. I did some research on this matter and discovered that there are pros and cons to connecting the negative terminal of PSU to earth GND. On the one hand, shorting the '-' terminal of the PSU to earth ground can reduce common-mode noise caused by the parasitic cap b/w local GND and earth GND, but on the other hand, it may create a ground loop, which can possibly pick up 60Hz interferences. Initially, I was of the opinion that connecting the '-' terminal to earth GND in my situation would not be advisable since the neutral pin for the PC power adapter is connected to earth GND, and this would create a GND loop if the PSU '-' terminal is shorted to the earth ground. However, other senior students in my lab have suggested that the PSU '-' terminal should always be connected to the earth GND unless a negative supply voltage is required. any feedback would be greatly appreciated.