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I am working on a new experimental set up for my thesis and I want to
control the whole process using LabView 8.

The set up has two chambers each one connected to a capacitance manometer and, 4
solenoid valves (not proportional, only ON/OFF) to control the flow.

My goal is to open the valves when the pressure reaches a certain value
in each chamber using LabView. For this task I purchased the cRIO-9481 with USB-9162

For the capacitance manometers I have ordered a Power Supply with an Rs-232
interface. I have not received yet the manometers but I am trying to build VI by
comparing two numbers (one set-up by me through a numeric control and the other is the
iteration count in a while loop). When the two numbers match I want to trigger one relay
on the NI-9481.

I don't know how ot integrate the NI-9481 in the VI. Any Suggestions ?

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Message 1 of 8

Re: NI-9481

Hello George,

Your application sounds very interesting!  I actually worked on a project a few years back developing a vacuum chamber control system using LabVIEW and SCXI, so I know where you're coming from.

The DAQmx driver makes controlling the relays on the USB-9481 very easy.  You can use the DAQmx shipping examples for digital I/O in LabVIEW as a guide for how to do this.  I would suggest looking at either of the examples Write Dig Port or Write Dig Chan.  These can be found by going to Help >> Find Examples and then navigating to Hardware Input and Output >> DAQmx >> Digital Generation.  This will provide the basic functionality for switching the relays. 

In terms of your control algorithm, you can use the functions in the Programming >> Comparison palette to implement the logic for decision-making. 

Hopefully this information will help you to get started with your application.

Best regards, 
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Message 2 of 8

Re: NI-9481

Thanks Jarrod,

It is an interesting and ... challenging project for me, as I am a mechanical engineer not an electrical one. I'll try what you have suggested and I'll keep you posted.

All the best,
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Message 3 of 8

Re : NI-9481

I must make a similar thing with LabView 8.2 !

Open 2 valves, make a vacuum in a chambers, recieve the data vacuum with manometer close one valve when I have the vacuum I want and open/close others valves to inject a drug.

The only difference is that I will use a NI cDAQ-9174. 


gcf, I know it was a long time ago now but was the informations from Jarrod B. enough for you to making something like that ?

Even for a beginer like me ? (I am probably better in biochemistry than programmation as an Engineer in Biochemistry)


Could I have a look at your work if you still have it ? It could help me to understand quickly.



Thanks for your answer.

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Message 4 of 8

Re: Re : NI-9481

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Message 5 of 8

Re : NI-9481

Not really, I just found someone who made a similar thing with more research because I did not have any answers to my question for the moment (and it is not a problem, I can wait, I just do not like waiting without doing something)

As I cannot send a message to gcf, I try to let a comment here with the hope that he will see it easly.


I continue my research so if I ask another question, be ready to say "duplicate" Smiley Wink





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Message 6 of 8

Re: Re : NI-9481

Of course it's a duplicate of your original post and you just have to show a little patience. This is not only a duplcate, but a very old thread and you are un likely to get a response from someone that has not posted in over 4 years - or did you not check that?
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Message 7 of 8

Re : NI-9481

Of course I check that, "I know it was a long time ago" - or did you not read that ? 

But as we say "Which tries nothing, has nothing"

He could have the same e-mail address and receive e-mails if a response is posted.

But anyway, our discussion is meaningless. Bye

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Message 8 of 8