using a NI 9265 to open a valve

[Vergilius]

Hello everyone.

I've just been given a project to make a 'student testrig' that used to run on software called 'Generix' to work on 'Labview'. They have given me Labview 7.1 to do it. The end goal will be to create a VI that will allow students to create and test teh differences between a P, PI and PID system. Since I have no experience yet using Labview I'll probably need your help in the upcomming weeks But first things first, at the moment I'm still getting familiar with the testrig, its components and Labview 7.1.

The testrig consist of a pump, pneumatic valve, flowmeter and a levelmeter. Using a NI 9203 I've gotten both meters to display correctly in a VI. But when I try to open the valve using a NI 9265 I get no satisfying results. In 'Measurement&Automation Explorer' (M&AE) I can control and open the valve by entering a value between 4mA and 20mA. But I'm doing something wrong when I try to do this by pointer or dial using Labview. In VI when i just use DAQ i go the the M&AE. I've attached my latest attempt.

Perhaps one of you guru's can give me a pointer on how to operate the valve using Labview?

Kind regards,

Ivo

[Vergilius]

Ow I've tried to use the example finder but for some reason it isn't working on that pc.

[Fixxer]

Hello Vergilius,

Try the attached snippet.It should work, if there are no compatibility issues (I am using LV 2009).

[Vergilius]

Thanks, I'll try it as soon as I get back there. That won't be till thursday however.

[Vergilius]

At the moment my problem is more basic it seems. I can't get the VI to change the mA sent to the valve. I can't get the VI to sent a signal to the valve. But I can change the signal in Measurement and Automation Explorer directly to change the valve setting. So I think my problem is that I do not know how to connect a dial to the DAQ signal or the DAQ to the Measurement and Automation Explorer.

Any help would be appreciated.

[ninlmartijn]

Dear Vergilius,

is the previous example working? Please try that one and let us know what the results are,

Best regards,

[Wayne.C]

Vergilius,

1. Knob on front panel inputs a value of 0-100 into the express vi.  Express vi is expecting inputs in the range of 0.004 - 0.020 (Amps).  You need to scale this.  See attached snippet.
2. You need to modify settings inside the express vi so that the Generation Mode is set to 1 Sample (On Demand) and set the Signal Output Range Min to be 4m ( .004 Amps ).
3. Consider not using the DAQ Assistant and instead use the DAQmx vi's.

Martijn S,

Vergilius has already stated that he is using LV7.1  Suggest that you post your vi as a snippet that he can view.

[Vergilius]

Hi guys,

It worked, the valve is opening. However I have some hardware problems now. The computer that has been hooked to the system is breaking down. So since I have to get a new one anyway I'm trying to convince the departmenthead here to upgrade the software aswell.

I only work here on thursdays and fridays, and since it's spring break this week...............