Relay drive limit and PXI-2584

[Enrique]

While using a PXI-2584 I got an error message saying that I exceeded the relay drive limit for the device. Testing the PXI-2584 in MAX it seems I am limited to actuate up to two relays simultaneously on independent mode.

- In the documentation, where do I need to look to read about these limitations? Specifically for the PXI-2584 I am not finding it (I bet is in plain sight 😉 )

- Can I override that limitation? If so, how can I do that in LabVIEW?

Regards.

[Frank-L · Accepted solution]

Enrique,

In the documentation, where do I need to look to read about these limitations? Specifically for the PXI-2584 I am not finding it (I bet is in plain sight  )

Great question! Normally the relay drive limit is listed in the specifications. (For Example "Simultaneous Drive Limit" on 2532 http://www.ni.com/pdf/manuals/373723h.pdf) Unfortunately, This is not listed in the specifications for the 2584. I plan to file a bug report on this issue.

Can I override that limitation? If so, how can I do that in LabVIEW?

Unfortunately this device's simultaneous drive limit is limited by the hardware and cannot be overridden. 

[Enrique]

Thanks Frank. Then, I also want to suggest NI to manufacture a similar card that do not limit the number of relays (or at least up to 4). I recommended this card against a card of another brand known to work to make the new system as homogeneous as possible. I just ended up making everything more complicated.

[ChristophersonJ]

Hi @Enrique, 

To add a little more information: The relay drive limit is based on the power limit of the card. 

For such a high voltage card, we're limited in the amount of power we can push across the isolation barrier. 

Application-wise for this module as well, it's not expected that you'd ever need more than 2 relays closed at a time for the 2-wire and 1-wire Dual topologies respectively.  

What kind of voltages, and what sort of topologies are you needing for your application? 

We can take that into account along with your feedback for possible future product offerings. 

[Enrique]

Thanks for your reply. The DUT is a three-terminal medical device that I need to test by applying 100VDC to all terminals at once for a HIPOT. The system is for a production line and must perform other test without having to remove the DUT. I am basically updating an old test system that already do all the required test.

Fortunately, because the system must test several DUTs at a time, it needed several PXI-2584. I was able to do a slight modification to take into account the relay count limitation by mixing relays from each cards, and saved the day 😉

[Enrique]

My original design was like in this image: