PXI-6259 wiring

[Jmc006]

Putting together another data acq. system that has PXI-6259 cards.  Attached is how I have typically wired in the past with TBX-68 terminal boards, however when I go to ni.com and look and the manual it does not agree with my typical witing scheme.  Any idea why they dont agree?

[Tim_W.]

It looks like your wiring set-up should work. Correct me if I'm wrong, but it looks like you're trying to wire several differential channels on each of your PXI-6259 + TBX-68 rigs. PT1 corresponds to channel 1 on card 1, PT8 goes to channel 1 on card 2, and DP1 goes to channel 1 on card 3, etc. Where specifically are you finding a disagreement?

Tim W.

Applications Engineering

National Instruments

http://www.ni.com/support 

[Jmc006]

Yes, that's exactly how i am wiring it.....and how i always have.   But from looking at the NI wiring sheet those terminals don't line up, unless I'm missing something?

for example I would typically use 33+, and 66- for my first channel

On the NI diagram 33 is AI #1, but 66 is AI #9 (not AI GND like I would expect)

Am I missing something?

[Tim_W.]

It depends on what you want to do. If you are doing differential termination then you've got it correct. If you're doing reference single-ended termination then you do need to wire to AI GND ground channels (pins 32, 29, 27, 24, 59, 64, 67). 

Tim W.

Applications Engineering

National Instruments

http://www.ni.com/support 

[Tim_W.]

Another question is what hardware have you used in the past?

Tim W.

Applications Engineering

National Instruments

http://www.ni.com/support 

[Jmc006]

I have always used this hardware setup, and always have done the differential termination.    So where is the NI wiring diagram for diff terminations?

[Tim_W.]

You have it correct. For channel 1 (technically channel 0, because we like to 0-index everything) in differential mode the DAQ card takes inputs on AI1 and AI9 and compares the two values. It doesn't reference directly to ground, but instead references one to the other. This document might do a better job of explaining it: Field Wiring and Noise Considerations for Analog Signals. The scheme we have for differential inputs is to typically have the inputs be 8 AI channels apart (AI2 goes to AI10, AI3 goes to AI11, etc.)

Edit: Consider reviewing this resource for double-checking wiring connections using DAQmx Tasks in MAX:

Using Connection Diagrams for NI-DAQmx Tasks

Tim W.

Applications Engineering

National Instruments

http://www.ni.com/support 

[Tim_W.]

Actually, channel 0 would be pins AI0 and AI8, not AI1 and AI9 (those would be channel 1)

Tim W.

Applications Engineering

National Instruments

http://www.ni.com/support 

[Jmc006]

Ok, I got it.  But where is the documentation from NI detailing the terminations for differential configurations?   The only reason I knew about where to land these connections was from following past setups other coworkers have done here.  NI must show the diff pinouts somewhere right?

[Tim_W.]

The M Series User Manual has a chapter on connecting analog inputs (Chapter 4). Specifically, I would check pages 4-5 and 4-12 to determine the proper method for connecting your signal. 

Tim W.

Applications Engineering

National Instruments

http://www.ni.com/support