cDAQ-9174 Duty Cycle

[brethigh]

I have an upcoming test that I'd like to use my cDAQ-9174 with.  We're testing an electric motor and the controller for it, and have electric brakes coupled to the motor shaft to apply torque.  We have a duty cycle where we need to apply X torque for Y duration, with the torque and time variables changing for each step in the duty cycle.  I'd like the option to have an automatic test where it goes through the programmed steps of the duty cycle then repeat for however many cycles are needed, or until it's manually stopped.  I'd also like to be able to manually enter a torque amount, whether it be a digital input or on an analog dial, and the input to the brakes change with what I'm selecting.  Is this possible with the cDAQ-9174?

Side note: I currently only have FlexLogger and am assuming I'll need to do this in LabVIEW (just another justification to help convince management).

[_Bryan]

Maybe?

Can you work within the specs of the 9174?  How many channels/modules do you need?  You say "changing for each step in the duty cycle", what is the duty cycle?  You could have issues depending on how fast the duty cycle is.

If you want to automate the test you will need LabVIEW and know how to program in LabVIEW.  Flexlogger looks like it is just for quick manual testing with data logging.

You also have to think about safety.  Are you going to run LabVIEW on a windows machine for control of the test?  Windows is not deterministic, so how important is timing for the test?  https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000P9QiSAK&l=en-US Take the +/- 1 ms timing with a grain of salt, that would be in a perfect world. 

"If you are using the LabVIEW/LabWindows timer functions to control a loop, then you can expect differences in the time interval between each iteration of the loop, depending on what other processes are running on the computer at that instant. For example, if you have several windows open at the same time and you are switching between different windows during your data acquisition, then you can expect a lot of overhead on the Central Processing Unit (CPU), which might slow down the loop that is performing the data acquisition."

Also what happens to the test if Windows decides to crash, lock up, restart or just hang for 1 second?  It can be done, but you need to realize what could happen.

Once you have all the specs call NI and talk to a product engineer and see what they recommend.

Bryan

[brethigh]

Bryan,

Thank you for the response.  I'm not needing anything specific down to the milliseconds.  It's simply applying a torque (current controlled brakes) to a motor shaft for X duration (in full seconds) and adjusting the torque for each step in the test.  I've decided that it's not something I can do solely with FlexLogger due to needing to loop the test cycle over 1,500 times.  I'm currently researching and studying how I can get to my end goal.  I have all of the hardware I need, now it's just a matter of the software.