Producing a voltage that coresponds to a setpoint for a mass flow controller.

[dds1084]

Hello,

I have a mass flow controller that requires a voltage output signal from my DAQmx board (SCB-68) to maintain a setpoint.  This set point is a voltage that corresponds to the desired flow rate.  I have produced a scale for this linear controller but I do not know how to use it.

I know how to create a vi that reads a voltage input, I can also write one that sends the same voltage input back throught the output.  I can not write one that sends a constant voltage output corresponding to a flow rate.

Could somebody help me out with this?

Dan

[TiTou]

    Hello Dan,

Try this, every time you modify the slide "voltage output" that will "create" an event and the corresponding case of the event structure will be executed and then the output voltage updated.

Hope this help you.

BTW, if you need to program more, I suggest you have a look at LabVIEW examples "Help" >> "Find Example...", there are very good sources of inspirations 😉

[dds1084]

Thanks for your reply, I have been using some of the examples including the one you suggested.  The problem I have now is that this voltage ouput never ends until I stop the vi, place another required voltage in place then start the vi again.  How do I get this voltage output to stop when I press stop?

[TiTou]

Well, the event structure makes that easy, no ?

In the even case driven by the stop button, place the "stop DAQmx task" if you want the output voltage to equal 0 or another DAQmx write if you want your "power off" value to be different.

See VI attached.

[dds1084]

Your last post was very helpful.  Recently I am having trouble creating this vi to run two channels simultaneously.  I tried to simply copy everything and paste it above the rest.  Then I wired it into the while loop.  Unfortunately, I am having trouble completing the wiring for the second channel.  I get a pop-up box that says, "do not wire to a floating object, put the object where it belongs and rewire".

I would include the vi to show you but I don't know how to attach it.

Thanks again,

[TiTou]

Hello,

First, tp upload code (or any document) it is quite easy, just select the file, by clicking the "browse" button... see image below (I'm sorry it's all in french... 'cause I am french ! "Parcourir" means more or less "Browse" ;)) :



About your app, well adding a channel doesn't require to duplicate the whole code... Developper are always trying to do things with the less code possible ;). Check VI attached and tell me if it matches your needs.

Message Edité par TiTou le 03-23-200601:26 PM