acquiring multiple channels programatically

[Angelantoni]

Hi Am using SCXI 1125 with 1328 terminal blocks to acquire temperature values from thermocouple's. My problem is that i need to select the channels to acquire programatically, and create a task dynamically with the channels to acquire the data. the virtual channels should include data such as noise filtering, if i pass a string to create task function with all the channels i want to acquire, i cannot set the noise filtering in the task i created. but if i create a task previously then unnessesary channels will be scanned, which is not fisieble. should i create global channel for each physical channel with information regarding filtering in it and then create task with these global channels, or is there any better way?.

[Otis]

Which version of LabVIEW are you using? It will be a lot easier to do this if you are using LabVIEW 7.0 or 7.1 with DAQmx.

If you have one of these versions look at the shipping example Cont Acq Thermocouple-Int Clk.vi by going to the NI Example Find (Help > Find Examples), go to the Search Tab and search for "Thermocouples" and you'll find it there.

[Angelantoni]

Hi Otis

Thanx for the reply, the example really helped. I wanted one more clarification, do you think it is better to create global channel with all the properties set prior, and then using it in the application, or should i change the property in the application. actually i am not going to change the properties of channels often, may be not at all. so may be it is better to create global channel with all property set? and then acquire the data from the global channels, also does the system load increases if i have more global variables? kindly suggest.

Thanx
Arun

[Otis]

It's really more a matter of preference. I prefer to set things in my program just because I can see what's going on and change it. If you want to create a global channel with the properties already set that shouldn't be a problem either.

If I was making it, everything would be set programmatically. But either method will work, and you should do whichever you think would be best for your overall application and future users.