Use of more than one PXI6025E DAQ cards in one computer

[jyg1234]

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

[Tom_W_[DE]]

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-

[jyg1234]

Hi Tom,

Thanks for your reply. I think we may have found the problem and it seems that it was a software one in the setup of our VI in LabVIEW. It seems that the counter reset box in the counter demo which we thought was useless and could be removed is useful and can't be removed.

Just to clarify the problem though, there is apparently no problems with the card as we had tested each card by itself in both slots of the computer that we are using and the cards individually had no problems at all in either slot. However, when both were plugged into the computer and used, the second card (which one is second and which one is first probebly doesn't matter that much) had a low impedance input into the DIO pins. Only on the card that doesn't work, the pins would still take inputs but would have needed to sink about 1mA of current which we decided was not safe to do. The same card does work properly even after sinking 1mA of current, when the other card is removed.

The problem seems to be fixed now by the replacement of the counter reset box in LabVIEW (not sure why though) and I will keep this forum updated if any further problems arise.

Cheers,

John Gao

[Tom_W_[DE]]

Hi John-

I'm glad to hear you were able to find the problem in software and that the hardware seems to be working well now.  If the problem returns please let us know.

Thanks-