Kai said:
"Symmetrical and ground referenced signal routing in combination with use of shielded cable with shield connected to ground at both ends, "

It is wrong to ground(earth) a cable at more than one point !because ground loop currents may generate hundreds amps of current in the sheild,because that there is a capacitance between the sheild and wire cores of cable a large noise will be induced on the sensors and weak signals .

Thus the ground loop must be avoided and for solving this problem using data/power isolation is a right way.
I saw many DCS cards from USA,Germany vendors that use isolation in their cards ,They used three way isolation! and specified this on thier catalog also.

I wait for your notes!

bye