Chassis ground

[Chengjun Li]

Hi all,

I saw many equipments have the grounding symbol on their chassis,like shown below





I was wondering why we need to ground these chassis?
I think the ground line coming out of the outlet has already grounded the equipment chassis, why we need to do that again?

 

[Gryd3]

There is a great article here to read over:

http://web.mit.edu/~jhawk/tmp/p/EST016_Ground_Loops_handout.pdf
(Check Page 8)

Relying on the outlet 'ground' may not always provide the best results... so using a chassis ground and ensuring they are grounded to the same location can help decrease inadvertant current flow between devices.