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Recently, I made a small measurement system with three boards. Below is the block diagram:

enter image description here

The power ground cord is connected to the chassis at power entry. I think I need to connect the GND to chassis. Physically, the front board and power board is near to the power entry. At first, I only considered the point where the power ground cord connected to chassis. But, imagine that if my input signals are with great common mode voltage regards to my 'GND', then the common mode current need flow along the relative long power supply paths to the chassis, so I think I can ground the 'GND' at the front board too. Then the current can flow to chassis more easily.

Which is better?

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  • \$\begingroup\$ Could you be more clear about the cases you're comparing? I think you're comparing "only connect the chassis to the mains earth" to "connect the chassis to mains earth and to the common-mode reference for the differential inputs", but I'm not 100% sure... \$\endgroup\$ – ThreePhaseEel Nov 27 '16 at 4:45
  • \$\begingroup\$ Also, why have the ADC on the same board as the processor instead of on the same board as the AFE? \$\endgroup\$ – ThreePhaseEel Nov 27 '16 at 4:45
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    \$\begingroup\$ I mean, I want to connect the regulated power GND to chassis, and where should I connect them? \$\endgroup\$ – diverger Nov 27 '16 at 4:57
  • \$\begingroup\$ Curiously, how many articles about grounding in mixed-signal systems did you acquire and read? My Google search on "grounding in mixed-signal systems" (whole phrase) revealed 1830 engineering articles, from TI, Analog devices, Maxim, etc. \$\endgroup\$ – Ale..chenski Nov 27 '16 at 5:41

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