AO Grounds on a PXIe-6739

[jdroleskey]

I'm currently working on interfacing some custom hardware to an NI PXIe-6739, and I was hoping to develop a better understanding of how the grounds on the card are referenced to each other. From what I can tell, the grounds are all connected, as there is a common AO GND pin, as well as the dedicated ground pins for each AO bank. My question is whether the dedicated ground pins are connected via a plane, or if they are connected via traces? I've done some research on both the 6739 datasheet and the user manual and I haven't found anything, however I could have missed something as the user manual is a pretty large document. Thanks in advance. 

[Brian__P]

Hi jdroleskey,

All of the AO GND's and D GND's are connected via traces. Is this what you are referring to? This information can be found on the bottom of page 3-4 in the manual linked below.

NI PXIe-6738/6739 User Manual

http://www.ni.com/pdf/manuals/375140a.pdf

If this does not answer your question, don't hesitate to let me know.

Thanks,

Brian Poteet
Applications Engineer  
National Instruments  
http://www.ni.com/support

[nuflare]

I have a question on  the PXIe-6739 ground isolation. I was told by a NI rep the grounds of the 32 banks each containing two outputs were isolated from each other.

Apparently this is not the case.

From PXIe-6738/6739 User Manual

Analog Output Ground—AO GND is the reference for
AO <0..63>. When AO GND is listed next to an analog
signal name, it is the dedicated ground reference for those
signals (e.g. AO GND 2/3 is the ground reference for AO 2
and AO 3).Both ground references—AO GND and
D GND—are connected on the device.*

My question:

 Is AO GND connected to AO GND dedicated ground reference.

(e.g. AO GND 2/3 is connected to AO GND)

I need isolated ground between channels for my project.

This leaves only the PXIe-4322 for isolated grounds.

JK

[santo_13]

As far as I know, none of the 6739 GND signals is isolated from each other (All GND are connected internally through some path) and hence the instrument never calls itself an isolated signal generation device.

PXIe4322 has isolated channels and hence calls itself an isolated channel device

[nuflare]

santo_13

Thank you for your reply.

Bank isolation would be ok for my project but is seems there are no PXI bank isolated boards.

Do you know if the PXIe-6739 has isolation of bus and chassis to AO ground?

JK

[santo_13]

Typically if there is any sort of special isolation that will be explicitly stated in the datasheet and user manual with the rating for the isolation. If no such information is published, it automatically means that there is no isolation.

6739 has no form of electrical isolation between channels and chassis ground or earth.