Why is AI Continuous Scan.vi causing LabView 6.0 to run at such a slow rate?

Question

I am working on a 6 degree-of-freedom load application system.  It is forced controlled by pneumatic actuators operated using servovalves in a closed loop force controlled feedback system. The machine is instrumented with displacement (LVDTs and RVDTs) and force transducers (load cells and strain gage torque cells) so I can obtain measurements of all degrees-of-freedom (3 rotations and 3 translations).
The user interface to operate the machine has been designed on LabView 6i.  I know this is an outdated version - but half of the code was written previously, so I wanted to simply update and add to its functionality.  It runs on a Dell Optiplex GX260 Computer running Windows 2000.
What I do with LabView is input a control file that contains a series of clutch activations, loading parameters, and data collect on/off options to manipulate the machine.  This seems to run very well and FAST (about 25 seconds for 15 lines of code).  However, when I choose to acquire the data from our load and displacement sensors - this becomes VERY slow (about 12 minutes for the same 15 lines of code).  I have been trying different things out with the code to no avail.  First, everything that can be is running in parallel loops.  Second, I disabled loops that aren't required when we are running the control file.  Third, I omitted all signal processing that occurs (this is where we convert the voltages from the load and displacement transducers to actual force and distances using calibration coefficients).  However, nothing is speeding up the data acquisition.   
Currently we have two DAQs (a PCI-6023E and PCI-6040) for data acquisition.  I am only currently using the PCI-6023E board. I am using the NI provided .vi AI Continuous Scan (waveform).vi.  I would like to sample at 100 Hz (scan rate) and have a buffer size of 1000 and a number of scans to read at 10.  Prior to the data acquisition the user  chooses what load and displacement channels he/she would like to acquire data from.  It is rare that more than 2 channels are being acquired from at a single time (usually a single load and single displacement channel).  Only the user selected channels are passed to AI Continous Scan (waveform).  I have the iteration input variable wired to the iteration terminal of my while loop, so AIConfig and AIStart only configure the first time. 
So how this works is the control file looks for a "data_collect" phrase set to "on" and then the parallel data acqusition loop is activated.  The file control loop is matched to the data acquisition loop using a "Wait on Occurrance." 
I am attaching several VIs.  The main executable I run is called KBiii_Esther.vi.  This runs many subVIs to configure the experiment, etc.  The file control is activated in the file control loop and runs using the do_file_control.vi.  Finally, the data acquisition is activated in a seperate parallel loop and runs the do_acq_wave.vi.  This is where I believe the problem lies.
Questions:
1) Does anyone have any ideas why the data acquisition is slowing everything down?  AND do you have any ideas or suggestions as to how to fix this problem?  Is it the reading of the data or the writing to a spreadsheet that slows everything down? 
2) Does anyone have any suggestions for better buffer size and  number of scans to read values to optimize performance?
Thanks in advance.
Solved!
Go to Solution.
Attachments:
KBiii_Esther.vi ‏488 KB
do_file_control.vi ‏324 KB
do_acq_wave.vi ‏249 KB

Answer 1

To many sub VIs could not be found so I can not give you more than some advises. But I see that you run all your loops at full speed. I do not think it is very wise. Insert the "wait (ms)" functions in all while loops, but not the loops handling the daq functions. Since they are controlled by a occurrence. In Loops handling user input only you may set the wait time as high as 500ms. In more important loops use shorter time.
Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)