Scan Engine and Ethercat DAQ DIO Rate

[wegunterjrASI]

I am running a cRio 9204 and trying to read the RMS PWM Voltage (like reading with a multimeter). I am only getting the max and min voltage.  Is there anything I can do to speed up my Custom Device or controller to get this to work?   I have set my DAQ DIO Rate to 1000Hz, and the Target Rate is 800Hz with teh Primary control loop timing source set to Custom Device Timing.

Thoughts?

[Sarci1]

Hello wegunterjrASI,

I'm going to assume that you are using an NI 9225 module in the scan engine (hardware-timed single-point acquisition) which means that you will acquire a new data point ever 800 Hz. If this is the case, then what you are seeing is expected. You will see a single voltage reading (not Vrms) every 1.25 ms. This module returns DC voltage that needs to be processed into Vrms. This can be done using a model. If you are familiar with LabVIEW you can use the Basic Averaged DC-RMS VI to create a LabVIEW model for VeriStand. You can do a similar process with any other supported modeling environment.

Changing the DAQ DIO Rate will have no impact on FPGA based acquisition.

If you need further assistance I recommend that you post to the NI VeriStand Discussion Forum or speak to an Applications Engineer directly via support@ni.com or 1-866-ASK-MYNI. This forum is not meant for support. If you have questions specific to the Scan Engine and EtherCAT custom device it is recommended that you post to it's specific feedback forum.

Best Regards,

Lynn

[wegunterjrASI]

Aha...that makes sense. I am actually using a 9205 (with single ended - but a similar card) running in a cRio 9024 (VxWorks). Do you have any secrets on building a model with LabVIEW that will run in VxWorks?

[Sarci1]

Ah sorry. VxWorks does not support LabVIEW models. If your only options is LabVIEW, you could consider using the Easy Custom Device Tool.

[wegunterjrASI]

HA!   I like the word Easy in the name.  I am looking into that option now.   Thanks for the help.

[wegunterjrASI]

Also, i thought i was posting this in the Veristand discussion forum. How do i fix that?

[wegunterjrASI]

I do have access to Matlab, Simulink and Code Generator...will that work for this scenario?

[Sarci1]

Next time just submit your questions to the NI VeriStand Discussion Forum. You are currently on the Add-Ons page.

[Sarci1]

Yes you can use this, you will just need to write the Vrms computation code yourself.