Use of more than one PXI6025E DAQ cards in one computer

Question

Hi,
I have connected two PXI6025E cards into one computer on the same PCI bus. However, the DIO ports on the second card do not work. We are using the DIO ports as up/down control for the counters.
It works fine on the first card but not on the second. When we remove the first card, the second one works fine even in the same slot.
The problem is that the input impedance of the port is too low. Unless we put a high current input into the card, the signal being inputted is lost. On the card that works, the card sources about 60uA of current but on the card that doesn't work, it sinks up to 1mA.
Is this is a conflict issue and can it be fixed?
We need at least 4 counters and 4 analog outputs for our application and there are two of each on each card. Are there alternative methods of doing this?
Cheers,
John Gao

Answer 1

Hi John-
To clarify, are you saying the the card that works improperly sinks as much as 1mA even when it is the only card running and when it seems to be working properly?  Does the problem always exist on the second card to be started (i.e. one card is running fine but a second card fails when accessed) or is it isolated only to the single problematic card.
The NI 6023E/6024E/6025E Family Specifications indicate the maximum current sink for a logic "high" input should be 10uA.  The 60uA you are sourcing from the "good" card also seems to be within the 75uA maximum source current rating. 
If the problem seems to be isolated only to a specific card then it is likely that your input may be damaged.  I would suggest testing other digital lines in the port to see if the signal is still degraded by the apparent low input impedence.  If this is not successful please contact NI Technical Support for further troubleshooting help.
Good luck-
Tom W
National Instruments