S7-1500 AI 8xU/I HF (6ES7531-7NF00-0AB0) Proper wiring

Dear all,

In the wiring Manual is the I0-....I7- also wired to the ground, is this necessary for a good reading?

Because i also need to place a 4-20mA galvanic isolator for the inputs (requirement of the customer).

Is doing this on the output of the isolator a good idea? (see attachment) Thanks in advance.

Note: The arrow M is wired to ground

Yes this input is connected to a 4 wire ultrasonic level sensor (HydroRanger 200).

But what i dont understand is do i connect the M-connector of the input before (IN) the galvanic isolator to ground or after the isolator (OUT)?

Thank you for the answers always happy to hear from experts. Can doing this also be dangerous?

for example in case of a ligthning strike, the surge arrester in the system is going to lead the overvoltage to ground. Is it possible that this spike in voltage damages the analog inputs because its wired to ground for eliminating voltage differences.