What is difference between AI GND, AO GND, D GND, COM and AI SENSE?

Updated Jun 12, 2020

Reported In

Hardware

  • C Series Multifunction I/O Module

Issue Details

  • Can I connect between DI and AI ground for use?
  • Why these ground reference names are differernt? 

Solution

NI DAQ boards have different grounds that are used depending on the application: Analog Input Ground (AI GND), Analog Output Ground (AO GND), and Digital Ground (D GND). They are all referenced to a single point on the module itself. But they have different ground pins on the module to minimize noise and cross-talk. Especially, digital ground is particularly noisy because of the high frequency content of digital signals. Most of 

In case of COM, It is the ground reference used in dedicated modules, such as Analog Input module (ex. NI 9205). This is same as the pin for DAQ AI GND. 

But, case of AI SENSE is different. It is not connected to any ground anywhere else and floating with respect to AIGND, AOGND, and DGND. AI SENSE is a line that makes the reference of all single-ended AI channels common to each other; they all share a common reference



 

Additional Information

Typhically, there are 3 different types of ground reference, Earth Ground, Chassis Ground(in general, System Ground) and Signal Ground as mentioned above. More detail, refer this. The chassis ground refers to a system ground to the frame enclosing the internal circuit to secure the operation of the electrical hardware and to release residual charges. The signal ground is within the circuit, usually a separate reference that is not in contact with the chassis.