Solution:

As you know our ADAM-5000 series provides isolation for I/O modules (3000V), power (3000V) and communication (2500V). The 3-way isolation design prevents ground loops and reduces the effect of electric noise in the system. However, ADAM-5051/5051D and ADAM-5056/5056D are not the ISOLATED modules, and should reference to power module (at least the same power supply as power module). So, when you plug ADAM-5051/5051D or ADAM-5056/5056D into ADAM-5000/485 or ADAM-5000/CAN, the I/O module and power module are not ISOLATED.