Solution
We need to take into account electromagnetic compatibility (EMC) guidelines for NI PXIe-4138/4139.
This products were tested and complies with the regulatory requirements and limits for EMC stated in the
product specifications. These requirements and limits provide reasonable protection against harmful interference when the product is operated in the intended operational electromagnetic environment.
Referring to
GETTING STARTED GUIDE document of NI PXIe-4138/4139, on page 2, the maximum allowable cable length is 3 m (10 ft).