USB 9234 coupling settings in Mac OS X Labview?

[kornack]

Hi folks, 

I have Labview on OS X here connected to a USB-9234. I'm just thrilled to see this hardware supported on OS X; NiDAQmx Base works great with it. However, I can't for the life of me figure out how to set the AC/DC and IEPE settings. I noted that the readme file references these coupling parameters as "properties". How do I set properties for this device? Any general pointers would be deeply appreciated. 

Regards, 

Tom 

[Tom_W_[DE] · Accepted solution]

Hi Tom-

I'm glad to hear you're seeing good results with your USB-9234 and NI-DAQmx Base.

In order to adjust the coupling and excitation settings, you will have to use the new (as of NI-DAQmx Base 3.2) NI-DAQmx Base Properties feature for LabVIEW.  The properties interface was one of the last features we implemented for the NI-DAQmx Base 3.2 release that we are planning to potentially add more properties to and fully document in a future release.  However, I made sure to add the excitation and coupling properties for the USB-9234 since those are such differentiating hardware features.

You can't find the properties VIs on the NI-DAQmx Base palettes in LabVIEW, so you will have to browse to them.  They can be found in Applications::National Instruments::<LabVIEW dir>::vi.lib/_DAQmxBase/Internals/Properties.  You will want to use the DAQmxBase Get/Set Property VIs found there.

For the USB-9234, you can either specify settings for all channels (by leaving ActiveChannel unwired),  or you can specify settings on a per-channel basis by wiring a string to ActiveChannel that descibes the channel you want to use.  Note that you can only specify ActiveChannel in the form "DevX/aiY", so you might need to call the VI multiple times to set properties for various channels.

One other catch with the USB-9234: you can not use IEPE excitation when DC coupling is enabled.  Because of the way we implemented the properties interface, settings are immediately validated when they are adjusted.  So, if you want to disable IEPE excitation for a channel you will have to first switch that channel to DC coupling.  The order of operations is important, and you will be presented with a descriptive error if things are done out of order.  

One other caution- the coupling and excitation settings do not take effect immediately when they are set with the properties interface.  Instead, they take effect when DAQmx Base Start Task is called.  You also can not update coupling or excitation while a task is running, so you would need to call DAQmx Base Stop Task, adjust properties, and then re-start the task.

I added property settings to the ContAcq&GraphVoltage example (attached here, in LabVIEW 8.5) and also took a couple of screenshots in case you are using a different LabVIEW version.

 

Please let me know if you have any other questions.

Message Edited by Tom W [DE] on 01-20-2009 10:09 AM

[kornack]

Wow, perfect! Thank you!

Tom

[jojojojojo]

Tom, thanks for your help on this topic. I am trying to do the same thing via standard DAQmx on a Windows machine with LV 8.2. I can't seem to find the directory and VIs you are referencing. How do I accomplish the 9234 coupling/IEPE configuration?

Thanks 

[Tom_W_[DE]]

Hi jojojojojo-

In NI-DAQmx you have access to LabVIEW property nodes that will give you the same configuration options.

Find the DAQmx Channel Property Node on the DAQmx Advanced palette in LabVIEW under I/O Constants and Property nodes (or or something similar...I don't have DAQmx installed on my machine currently).

You can navigate to Analog Input:General Properties:Input Configuration:Coupling and Analog Input:General Properties:Signal Conditioning:Excitation:Source to set the same properties in DAQmx

[jojojojojo]

Tom,

Thanks for your help and sorry for hijacking this thread. Adding that property node does allow me to select AC or DC coupling for the 9234. However, it does not seem to work for IEPE excitation. Setting the "AI.Excit.Src" property to "internal" does not seem to activate IEPE. Also, when trying to create a VI with DAQ assist, the exictation is not an option for the 9234. I am running LV 8.2. Any ideas?

Thanks!

Josh 

[jojojojojo]

Figured it out! Had to change DAQ MX Create Channel from AI Voltage to AI Acceleromteter.  Thanks.