LabVIEW

cancel
Showing results for 
Search instead for 
Did you mean: 

Problem reading one channel with two DAQ Assistant simultaneously

I am using tensile machine doing the fatigue test and each test could cost 10 hours, for saving the disk room in computer, the loop has to be developed to periodically collect the real-time data then write out, but any certain point when load reach a number, the periodic data collecting will need to switch to continuous collecting. Therefore, I used time loop with DAQ assistant to preform the periodic collecting, at the same time I need another loop with DAQ assistant to monitor the same load channel continuously so that the signal interface can be sent to time channel to control the time delay to switch from 1000ms to 0ms. However the problem is the one channel can not be share with two DAQ Assistant simultaneously, could any one give me a help on this problem? I listed my block diagram below.  

 

 

Download All
0 Kudos
Message 1 of 3
(2,093 Views)

first glance, your DAQ Asst loop have data dependency from DAQ Asst2 loop, meaning your timed loop will not execute unless the DAQ Asst2 loop terminates. if you want to switch the save interval upon meeting a certain criteria from the measured channel, instead of having 2 while loops inside a while loop, can consider using only the DAQ Asst2 while loop; but instead of terminating the loop, wire it to a case structure that will start a counter that will count every 10secs and resets; where the reset case would be saving the measurement as well. 

 

you may want to consider sequencing the DAQ Asst, time elapsed and wait functions to get proper timing

CY (expired CLAD)
0 Kudos
Message 2 of 3
(2,071 Views)

You are using the Dreaded DAQ Assistant, meant for Newbies to convince them that they don't need to learn LabVIEW in order to collect lots of data.  You are also using the awful Dynamic Data Wire, also deceptive.  And who, with any experience in programming, names a program "final final final FINAL"?

 

Please, spend a day or two or 10 and learn some LabVIEW.  You do not want a Timed Loop -- these are high-precision structures designed for LabVIEW RT (I know, they're in the Structures Palette, but they are not doing what you think they are).

 

As far as I know, you cannot read a channel simultaneously with two DAQ Assistants.  What you can do is to set up DAQmx (it only takes 3-4 DAQmx functions and a little more LabVIEW experience than you currently have) to acquire data continuously, then take the continuous data stream and send it to one or more files simultaneously.

 

You have not given a good description of WHAT you are trying to do.  I think you are acquiring one channel of data from a device, but at what sampling rate?  Do you need continuous records?  Does the machine run continuously?  Do you want data to be saved for the entire Test, or do you want to start and stop data acquisition (and saving) while the machine continues to run?

 

All of these things are possible, and fairly simple to do in LabVIEW.  Take the several-hour Tutorials (it's OK to take more than one -- you'll learn more) and then come back and design your program.

 

Bob Schor

0 Kudos
Message 3 of 3
(2,059 Views)