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Difference between NI myDAQ and NI 9184 chassis


Hello, i have used a platform to acquire current and voltage of a PV cell and vary gate-source  voltage to sweep across the I-V curve  using a NI myDAQ. Now i am using the same platform but this time i have a NI 9184 chassis with modules NI 9205 and NI 9923 to acquire the current and voltage and NI 9263 to vary the gate-source voltage. Is there anything additional that i should do with the chassis because i am not getting the values as in the first one and i am not able to sweep?

Please help.
Thank you

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Message 1 of 5

With different Hardware, you need different Software.  The NI myDAQ is a USB-connected device with a DSP chip that handles many of the DAQ timing for you.  The cDAQ has its own processor, and is generally configured to run LabVIEW code itself, communicating with the Host using TCP/IP, with the Project generally configured as a LabVIEW RT Project.


Without seeing the Software for either the myDAQ code you wish to port nor the "evolution" of this code to support a cDAQ, I would only "guess" that you may be trying to use myDAQ/USB code for a cDAQ/TCP device (I wouldn't expect it to work at all ...).


Bob Schor

Message 2 of 5

Hello Bob,

Is there a way that I can convert the code used for the NI myDAQ and used it for the cDAQ?

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Message 3 of 5

Ever since coming back from NIWeek 2018 (which I thoroughly enjoyed, by the way), I've noticed that my ability to view code that Forum users fail to post has deteriorated so that I cannot view the code that you haven't posted, so I don't know What you are trying to do (which is far more important than How you are trying to do it).


So here's what you need to do:

  1. Make sure you know What the myDAQ program is doing (i.e. such things as Inputs and Outputs, Sampling Rates, I/O Channels being used, etc.).
  2. Be sure you understand how the myDAQ is "wired" to your Test system, including the various voltage levels involved.
  3. Be sure you understand what the myDAQ is doing, i.e. have some idea of what Analog and Digital Input and Output mean.
  4. Look at the code that (I assume) works using the myDAQ.  Be sure you understand all of its functionality, know what all of the LabVIEW functions are doing, and know how all of the Express VIs are configured.  Note -- if there are Express VIs, especially if you are using the Dreaded DAQ Assistant and its Evil Twin, the Dynamic Data Wire, this might be a good time to replace both with DAQmx functions and Waveforms (or Arrays of Dbl) before continuing.
  5. Now repeat these steps for the cDAQ configuration.  I've not done very much with cDAQs, but I think of them as LabVIEW Real-Time devices (I might be wrong, they might be able to function as pure "DAQ" devices). 
  6. Once you understand the cDAQ Hardware, you can use the knowledge you gained in Step 4 to begin to design similar software for the cDAQ system.  If you are, indeed, working in a LabVIEW RT configuration, I would first spend some time learning how LabVIEW Real-Time works, and how responsibilities are divided between the Host PC (which mainly is concerned with User Interface, over-all control of Program Execution, Data Display and Data Storage) and the Remote Target (i.e. the cDAQ), mainly concerned with Timing and DAQ functions, with the two systems communicating using TCP/IP (I'm partial to Network Streams, myself).

Note that this is definitely "more advanced" than working with a myDAQ.  You may want to seek out a local LabVIEW Guru who has experience with cDAQs and apprentice yourself for a week or two (or maybe a month ...).


Bob Schor

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Message 4 of 5

Bob has given you some good advice that you should follow.


In addition to his comments I am curious about what voltage you are trying to read?  I took a quick look at the myDAQ and noticed that it has multimeter mode inputs that can read 60 volts.  The 9205 is limited to +/- 10 VDC, so I hope you voltage is in that range.


The 9184 is just an Ethernet chassis that needs to be setup in MAX under networked devices.  (I use some 9188 chassis)  Once it is setup you can use the test panels to check inputs and outputs.  For the 9205 use a 9 volt battery and see if the voltage reads correctly.


You probably already noticed that in order to use the chassis you need to reserve it before you can do anything else.



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Message 5 of 5