Separate primary/secondary ground in PXI Chassis

[Wikinger]

Hallo,
I'm using a PXI 1006 chassis with a sample of Digital and Analog I/O cards.
It looks as if the PXI power supply does not separate primary and secondary grounds.
In my system it would be nice to have the secondary ground of the PXI system separated from chassis ground.
Is there a way to do so. I could not find any information about the grounding concept inside the PXI chassis.

[AVR]

I guess that my first question would be why you would want this capability? Different ground references within the same electrical circuit is a guarenteed way to introduce ground loops. I am not an EE (just an AeroEng - rocket scientist), but the better part of my career has been working in aerospace test facilities. The number one source of data quality problems comes from ground loops and improper grounding. Altering the ground reference path could lead to ground loops with potentials in excess of what the chassis (and IO cards) could withstand. While your application may require the capability for separate grounds, NI probably would not provide (document) the capability to separate the grounds to protect those users from inadvertantly setting a jumper that could d
estroy the DAQ system.

[Wikinger]

Thank you for your answer.
I surely agree with your opinion about keeping one common ground. But this must not automatically be the Chassis Ground of the System. It would be easy to have one common ground inside the system without fixing it to chassis by using a system power supply with separated primary and secondary side. To ensure that potentials do not excess to much a 1 MOHms grounding resistor is standard.
Anyhow my application grounding defined by the customer requires to be separated from Chassis.
Any further ideas?