NI DAQ Assistant

[roadrunner23]

Hi ,

I need to use DAQ Assistant for data aquisition from 3 different channels during 2 separate processes that happen one after the other in a while loop. i  did the daq programming and for the 2 processes i use 2 flat time sequences and i do not know how to enable the data aquisition during both of them. Can somebody help me?

Thanks in advance!

[Bob_Schor]

I'd strongly advise you to read this excellent DAQmx White Paper and then stop using DAQ Assistant.

Bob Schor

[roadrunner23]

I see, i will do that, however how can i have data aquisition during both processes if i use time sequence to separate them?

Thanks again

[Bob_Schor]

I don't really understand what you want to do.  Do you want, for example, to acquire 100 points from Channel 1 at 1KHz, and when that is done, collect 200 points from Channel 2 at 2 KHz, etc., or (almost simultaneously) collect 100 * (a point from Channel 1 and then a point from Channel 2) at 1KHz, or (almost simultaneously) 100 points from Channel 1 at 1KHz + 200 points from Channel 2 at 2 KHz?  Give a better description of what you want to do and we can better suggest if/how to do it.

Bob Schor

[roadrunner23]

Sorry, i will try to be more specific, so i need to aquire data from the 3 channels simultaneously, with the same rate and number of samples during discharging a battery (the dc load i use is also controlled in labview) and then during the rest period after discharging. So basically i want to discharge a battery for X minutes and then wait for Y minutes and so on up until a condition is verified and all this time i need to have data aquisition from the DAQ module.

Thanks again!

[Bob_Schor]

Have you ever used MAX?  Open MAX (also called NI MAX, or Measurement and Automation Explorer) on a computer that is connected to your DAQ Device.  Find the Device in MAX, open a Test Panel, and create a Task where you configure the three (I'm assuming) A/D channels that you intend to use.  Set them as Differential or Single Ended, change the Max/Min voltages, the sample rate, number of points/read, and request Continuous sampling.  Push "Start" to check out the behavior, then make a Task with all these parameters.

When you now configure a Start Task function in your code, you can click on the Task input and wire a constant.  If you click the little down arrow in the Constant, it should show you the Tasks that MAX has configured (I hope you named your task something other than "Task 1") -- select it, it will set the channels, sampling rate, etc. for you.  Now all you need to do is put a DAQmx Read function inside a While loop, and you are Off to the Races.  [There may be a few more details to handle, but that's most of what you need.  You'll want, of course, to configure N Samples/N Channels ...].

Bob Schor

[roadrunner23]

Ok, I did that, now how can i split the 2 processes, discharge and rest and still aquire during both cause using 2 time sequences in a while loop doesn t work?

Thanks!