Reading in data from DAQ card.

[TeamA]

What is the easiest method of displaying the same data into different sub VI's at the same time either usibng global variables or other methods?

[Dev_777]

The easiest method can be global variable but the better method will be to use notifiers as it takes care of any phase differance or frequency differance issues.

[TeamA]

We do need the data to be instantaneous throughout our project, as the data thats coming in is constantly changing and we would be also changing parameters going back out.

How do we use these notifiers, we heve spent 2 weeks on labview and during that they changed from version 7.1 to 8.2 which confused us. We know very little, just enough to do simple programs.

Many Thanks.

Team A

[RJay]

Do a search on Functional Global.  You set the value which can be read by any other vi (or sub-vi).

Message Edited by RJay on 06-25-2007 07:18 AM

[TeamA]

Is it possible to store plant data into an array and then have other VI's take specific data from that array and use it,  'something like a global array perhaps'?

[JonBowers]

You can use a string array as global variable but i would advise against this. I can be difficult to sequence read/writes with global variables and so you don't always know the data you are reading is the latest. A better approach might be to use a functional global. This is a sub vi that stores data in an uninitialised shift register. Each time you call the vi you pass it a parameter to tell it what to do. These would inlcude, initialising the value, reading and writing. I have attached an example of implementing a string array as a functional global.
If you are worried about passing data around you whole application then you need to consider the architecture you are using. Try searching the example programs and web site for Producer Consumer and State machine for more information on architectures.
The function global method I mention is a very powerfull tool when developing within LabVIEW. it means sub-vis can maintain there own data instead of you have to pass it around the whole diagram.

Regards

Jon B
Applications Engineer
NI UK & Ireland