Solution
NI DAQ modules specify absolute maximum ratings for input pins. If the applied signal remains within these limits, the hardware should not be damaged even when the chassis is powered off.
However, NI strongly recommends avoiding continuous signal application when the module is unpowered because:
- Internal protection circuits are designed for powered operation. When the module is off, these circuits may not function as intended.
- Prolonged exposure can cause leakage currents or stress components over time.
Best Practice:
- Disconnect external signals when the PXI system is powered off.
- Use signal conditioning or isolation to protect the module.
- Ensure applied signals do not exceed the absolute maximum ratings specified in the module’s datasheet.