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