Issue Details

• Are the grounds on my X Series, M Series, E Series and S Series DAQ devices all tied together?
• Do it matter which ground I connect to on my X, M E or S Series card?

Solution

Yes, all the grounds including analog input, analog output, and digital I/O are tied together to the common ground.

This connection occurs after the ADC references the appropriate ground for each respective task type, so the ground line for your incoming signal connections should still be tied to the related ground (AI GND, AO GND, or DGND) or you may experience increased noise.

Additional Information

The AI GND, AO GND and DGND are signal grounds. When multiple signal signal grounds are present, each has it's own current return path. Interference currents can be picked up from adjacent ground paths. Interference is transformed into voltage fluctuations, causing an increase in noise. If the signal is not connected to it's respective ground, there is a chance that the return current will flow with other return currents, introducing undesired noise. Ensure that the connected signal ground matches the signal type.

The ground lines are still tied together before being routed to the PCI or PXI ground, and thus can be damaged if there is too great a potential difference between each ground.  Before connecting multiple ground lines, take steps to ensure that the potential is the same at each ground terminal.  If this is not possible, consider taking your readings using Differential mode.  If readings are different from one ground to another on the same card, the cable or card may be damaged or the pins bent.