Simulating ni 9263 for mass flow controll application

[vashista]

Dear all,

I am building a VI to control flow rates of four mass flow controllers (alicat 0-1000 slpm), using cdaq-9185 and NI-9263 which is an output module. Before connecting hardware i am simulating the same using nimax and labview. I am able to give signals to the NI-9263 using daqassist. But, i am unable to read the output from daqassist. I have attached my ni program. Please provide me some suggestions

[GerdW]

Hi vashista,

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@vashista wrote:

I am building a VI to control flow rates of four mass flow controllers (alicat 0-1000 slpm), using cdaq-9185 and NI-9263 which is an output module. Before connecting hardware i am simulating the same using nimax and labview. I am able to give signals to the NI-9263 using daqassist. But, i am unable to read the output from daqassist. I have attached my ni program. Please provide me some suggestions

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Why can't you read anything using DAQAssistent with a simulated device?

What exactly do you want to read? Do you really want to read the same output as you have written using a 2nd DAQAssistent??? Usually you write an output and read an input!

Your VI doesn't show nay attempt to read anything from DAQmx…

Why do you need ExpressVIs at all? Why do you need 3 MergeSignal functions to create a DDT containing 4 values? You can increase the size of the MergeSignal function - or use BuildArray before:

Why did you set your DAQAssistent to write continuous samples at 1kHz and 100 samples per write - but then you only supply 4 scalar values?

Please do the basic LabVIEW training as offered in the header of the LabVIEW forum! And please also read this basic DAQmx article!

[DavidBoyd]

As a longtime user of Alicat's excellent massflow and pressure devices, I'm also wondering why you think a DAQ device is a good way to control them (and read back their flow indication).  These devices have a highly functional serial interface that is relatively easy to implement in LabVIEW.  You can inspect and change the setpoint, gas type, PID control loop values, know the amount of valve drive, read the actual flow... and a lot more.  It's all fully documented and best of all, someone's already written the LabVIEW instrument driver for you!  (I was that someone, although Alicat has long since made that driver their own and extended it for new device capability).

I would never recommend using DAQ because of the added expense of DAQ hardware, the additional calibration uncertainty, the mess of wires and grounding issues, the loss of precision, etc.

Dave