Does anyone have any good solution for signal conditioning upper signal to standard NI equipment levels ( - 10V >< + 10 V ) and other. Any solution is welcome.
One solution is to use an isolation amplifier. I usually use the low cost ISO124P from Burr Brown (now TI). In front of the ISO124, you can built a voltage divider that will reduce the voltage at the required level for NI board. The ground loop is interrupted by the ISO so you don't have to worry about voltage differences between the NI board and the signal source.