PCI-6224 Termination Problem

[rpursley8]

I am using most of the analog input channels on a PCI-6224 M-Series board (26 of 32 lines).

I use MAX to configure all of the channels. They are all configured as RSE, but when using them I noticed that one of the two that are usually paired together in differential mode was mirroring the voltage changes of the other, but not the other way around. I double checked in MAX and all channels are configured as RSE.

So I then built up a vi to read the two channels and also read the termination type. When I do that, one of the two channels say RSE but the other says it is Differential.

Has anyone else seen this type of behavior or have any suggestions on how to resolve this problem?

[LYu]

Hi Randall,

I just want to verify if you are configuring the termination in the global channel set up in MAX. When you set up the problematic channel as RSE in LabVIEW, do you notice the same behaviour? If so, do you mind posting the test program you're running so I can further look into the issue?

Thanks,
Lesley Y.

[rpursley8]

I configured them all as global channels in MAX and all of them are configured as RSE. The test program won't help since all of the configuration is in MAX.

[LYu]

Hi Randall,

I tried to simulate your scenario using a PCI-6251 board by:

1. Creating 16 RSE voltage channels in MAX (lines 0-15)
2. Used the program attached to read the terminal configuration of each global channel

I did not encounter the same situation. Please let me know if I'm doing anything differently (even small details such as measurement type, the order of your set up, and the LabVIEW program you ran to read back the termination), and the drvier version used. I will try to obtain a PCI-6224 to replicate your situation. Also, I'm wondering if you set the global channel up in LabVIEW (instead of MAX), whether you encounter the same problem with the specified lines?

Thanks,
Lesley

[LYu]

Here's the test program I used

[rpursley8]

That is what I did. I'm not surprised you didn't see the problem, it seems more of an anomaly than a bug. I am going to try to write to the termination property and then see if they change. If that doesn't work, then I will delete and recreate all of the channels. I will be able to try that tomorrow and see how it goes.

Thanks for checking.

[rpursley8]

I seem to have narrowed it down somewhat. When I check out each individual global channel, each seems to work in RSE mode as expected, but when I run a task that contains my global channels, that is when one of each pair runs in differential.

I also found out that if I run DAQ Assistant and do not use my global channel definitions, it runs correctly, but if I add my global channels in to replace each corresponding physical channel then it doesn't work correctly again. So it appears to be something to do with how the global channels are interpreted.

At this point I am deleting all of my global channels and will reference each as its physical channel.

[LYu]

Hi Randall,

I tried the scenarios mentioned using a PCI-6221 device and DAQmx 7.4, but didn't encounter the situation mentioned. I'm wondering if the situation you're seeing occurs consistently with a particular channel? A few things I came across which could be related:

i) Adding global channel to a task
- Either a global channel, or a copy of it can be added. If the actual channel is added (as supposed to a copy of it), the channel will appear with a globe icon next to it, and all the settings are greyed out. If a copy of the global channel is added, there's no globe icon, and the settings can be changed. In this case, this can be reconfigured and hence end up with configurations different from those seen in MAX.

ii) Adding global channel to DAQ Assistant
- Only a copy of the global channels can be added. In this case, the settings can be reconfigured and although the names of the channel may be the as channels in MAX, the settings can be different. These channels will be project based only (only exist when this VI runs).

At one point, I had configured the global DAQ Assistant/task channel differently from MAX (without realizing it), and was confused by the different setting I read back from the property node in LabVIEW and what I saw in MAX. I'm wondering if this could be an explanation for what you saw?

Thanks,
Lesley

[rpursley8]

I was very careful to verify everything I tried to make sure it behaved the way it seemed to. My next step may be to try to install NI-DAQ 7.4.1 and see if the problem goes away.