Triggered finite acquisition in a while loop - speed limit ? (newbi)

Hello,
I suppose the question already asked and answered but I didn't find exactly what I was looking for, so I'm sorry if it exists somewhere here.
Usil LV7 with NI 4474 (PCI) acquisition board, PCI-6601 as external trigger, I would like to perform a repeted finite acquisition, starting on external trigger.
Trigger is working fine (I need up to 20 impulses /s), but the finite acquisition in a while loop doesn't seem to follow the speed. I was thinking it was a CPU proble m and I removed everything which was not absolutely useful.
So I have a VI with
1) External trigger output. (express)
2) While loop with DAQmx Read Analogic Waveform 1 channel N sample, with a DAQmx task as an i
nput (specifying 50000Hz sample rate, 1000 samples, external trigger start)
I was able to climb up to 10 cycles/s but above, some ext. triggers are missed.
Question : where is the problem ? On continuous acquisiton, I can acquire up to 100.000 samples/s but on finite acquisition, I cannot perform 20x1000 samples/s ? What actually specifies the while loop itteration speed ?
Thank you for your ideas, I'm joining VI capture...
Attachments:
vi_ai_external_triggered.JPG ‏31 KB

I did not the test, but first of all, I think it is not the good way to call your task at each iteration. It is better to configure all elements concerning your aquisition outside the while loop. (external trigger, sampling rate, number of samples.... After you start the DAQmx read (only) in the while loop.
I think you'd better start from an example from the labview library (attached file)
Hope it will help you
Regards
Attachments:
Acq&Graph_Voltage-Int_Clk-Dig_Start.vi ‏71 KB

Similar Messages

Triggered finite acquisition and period measurement

Hello,
My problem is this: I'm not sure on how Labview accesses devices and how setting up multiple tasks affects loop iteration speed.
The vi I have attached uses a rotary encoder to generate a pulse triggering the acquisition. I have noticed that trying to also perform a period measurement on this pulse causes the iteration time to double. For that reason I have included the case structure so the program reads once every 50 iterations.
I am using the PCI 6250 (dev2) and PCI 6220 (dev1) which are connected by an RTSI cable. The 6220 and 6250 are connected to CB-68LP and TBX-68T terminal blocks respectively. The latter of which causes some problems due to incompatibility.
Any help on either te reasons for the slower iteration time and how to solve it would be most appreciated.
Thank you
Ingram
Solved!
Go to Solution.
Attachments:
new.vi ‏64 KB

Hi Ingram,
Thank you for your forum post and for including your VI. On reviewing your code I am aware of the following:
Acquiring 3 Analogue Voltages using a PCI-6220 (Temperature and Torque readings)
Acquiring 1 Analogue Voltage on the PCI-6250 which represents "Percentage Metallic Content", this task starts when a Trigger is recieved on PFI9
Acquiring 1 Counter Input on the PCI-6220 which represents the RPM of a motor
You are also logging test data to a ASCII text file, this data is only logged when the user presses the stop button on the Front Panel.
As the Counter and Analogue input tasks are seperate from one another it would be worth placing them in their own loops, I think with a bit of rearranging we should also be able to avoid the scenario where you have a while loop embedded inside another while loop. The initialisation of the DAQ tasks should only really be performed once, outside any loops. Another issue dependant on how long the application is executed is the dynamic arrays that are being created, these could become really large slowing down the application the longer it is run for.
An architecture I would recommend for your application is "Producer/Consumer" outlined in the community example available here.
The producer loop will be acquiring data and runs really fast (High Priority), the consumer loop logs data to file (Low Priority), data is shared between the loops using a Queue structure, no other wires should be shared between the 2 loops as these might cause a data dependancy.
Do you require all 3 input tasks to be perfectly syncronized with one another?
Many Thanks
Jamie S.
Applications Engineer
National Instruments

When I add a while loop to the vi "niScope EX Multi-Device Configured Acquisition (TClk)" to acquire data for multiple times, it works but it runs very slowly.

Because I want to acquire the similar data for multiple times and then take an average to increase SNR, I add a while loop to the vi "niScope EX Multi-Device Configured Acquisition (TClk)". It works but it runs very slowly (about 1 sec for each iteration). I think I had put the while loop at a wrong position, which makes the vi run from the very beginning in each iteration. So I really want to know where should I put the while loop to improve the speed? I have attached all the vi and subvi.
Thanks very much.
Attachments:
Multi-Device External Clocking (TClk).vi ‏1166 KB
avgWfm.vi ‏15 KB

Dear Zainykhas,
Thank you for posting this to the discussion forums and for uploading some sample code. I took a lok at the issue you have been having, and it is unclear to me as to why you have placed two for loops around the original while loop. My understanding is that you want to use the original Sample.vi and want to execute this N times where N is the Max Freq divided by Interval so that you can scan for a range of frequencies.
Why not just put Sample.vi around one for loop and use the increment counter scaled by the interval to count up towards Max Freq and insert the desired Frequency into the cluster using Bundle By Name?
Kind Regards,
Robert Ward
Applications Engineer, NI
Attachments:
Modified - RW.vi ‏48 KB

While loop and data acquisition timing worries

Hello everyone,
I apologize in advance if this is a silly question, but I could not find the answer around here.
I have made a VI to record continuously from 64 analog channels at a 5kHz sampling rate. I then stream this data to a tdms file. The data acquisition and write functions are in a while loop.
I the same loop, I have a bunch of other loops, that each run on their own wait timers to help limit the amount of memory they take up. I am now worried that this may somehow affect my data acquisition timing.
If I put a bunch of timed loops within another loop, does the outer loop run at the same pace as the slowest of the inner loops? And could that mess up my sampling rate?
I have attached my VI, in case what I just wrote makes no sense at all.
Thanks for any tips...
Attachments:
Record_M8viaDAQv3.vi ‏237 KB

Well, looking at your code you will only write to your TDMS file one time. You have multiple infinite loops within the main/outer loop. That means that the main loop will only run a single iteration because it cannot complete an iteration until all code within it completes. With at least two infinite loops inside the loop it will never complete. Not too mention the only way to stop your code is to hit the stop/abort button. NOt a very good way to stop your code. As someone once said using the abort to stop your code is like using a tree to stop your car. It will work but not advised.
As Ben mentioned try to understand data flow better. You have unnecessary sequence frames in your code where normal data flow will control the execution sequence.
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot

Iteration Speed issue when Indexing 3D array wried to a while-loop

Brief Description of my Program:
I am working on the real-time signal generation by using LabView and DAQmx (PCI-6110 card). My vi reads the big data file (typically 8MB txt file containing about 400,000 samples (complex double precision). Then, the signal is pre-processed and I end up with a huge 3D array to feed while-loop (typically 3D array dimension is N x 7 x M where N & M >> 7). Inside the loop, that 3D array is indexed and processed before the results are written to the DAQmx outputs. I have a speed issue when indexing the large 3D array (i.e, 3D array having a large sub-array size). My while-loop could not run fast enough to top-up the DAQmx AO buffer (at the output rate of 96kHz). It could run faster only if I use smaller 3D array (i.e, smaller-sized sub-arrays). I do not quite understand why the size of 3D sub-array affects the rate of looping although I am indexing same sub-array size at each iteration. I really appreciate your comments, advices and helps.
I include my 3D array format as a picture below.
Question on LabView:
How does indexing an 3D array which wires to the while-loop affect the speed of the loop iteration? I found that large dimension of sub-arrays in the 3D array slows down the iteration speed by comparing to indexing the same size of sub-array from smaller-sized sub-arrays of the 3D array to perform signal processing inside the while-loop. Why? Is there any other way of designing LabView Program to improve speed of iteration?
attachment:

Thank you all for your prompt replies and your interests. I am sorry about my attachment. But, I have now attached a jpg format image file as you suggested.
I had read the few papers on large data handling such as "LabVIEW Performance and Memory Management". Thus, I had already tried to avoid making unnecessary copies of data and growing arrays in my while-loop. I am not an expert on LabView, so I am not sure if the issues I have are just LabView fundamental limitations or there are any other ways to improve the iteration speed without reducing the input file size and DAQ output rate.
As you request, I also attach my top-level vi showing essential sections such as while-loop and its indexing. The attached file is as an image jpg format because the actual vi including Sub-VIs are as big as 3MB in total. I hope my attachment would be useful for anyone who would like to reply my question. If anyone would like to see my whole vi & llb files, I would be interesting to send it to you by an e-mail privately and thus please provide your e-mail address.
The dimension of my 3D array is N x 7 x M (Page x Row x Column), where N represents number of pages in 3D array, and M represents the size of 1D array. The file I am currently using forms 3D array of N = 28, & M = 10,731. Refering to the top-level vi picture I attached, my while-loop indexes each page per iteration and wrap-around. The sub-VI called "channel" inside the while-loop will further index its input (2D array) into seven of 1D arrays for other signal processsing. The output from that "channel" sub-VI is the superposition of those seven arrays. I hope my explaination is clear.
Attachement: 3Darray.jpg and MyVi.jpg
Kind Regards,
Shein
Attachments:
3Darray.jpg ‏30 KB
MyVI.jpg ‏87 KB

I am using a timed while loop and am unable to get the loop to run at a speed of less than 1ms (I am currently using the Wait(ms) function). How can I get a faster response?

I am trying to create a virtual engine within a timed while loop and am unable to get the loop to run at a speed of less than 1ms (I am currently using the Wait(ms) function). This does not however allow realistic engine speeds. How can I overcome this? I have access to a PCI-MIO-16E-4 board.

andyt writes:
> I am using a timed while loop and am unable to get the loop to run at
> a speed of less than 1ms (I am currently using the Wait(ms) function).
> How can I get a faster response?
>
> I am trying to create a virtual engine within a timed while loop and
> am unable to get the loop to run at a speed of less than 1ms (I am
> currently using the Wait(ms) function). This does not however allow
> realistic engine speeds. How can I overcome this? I have access to
> a PCI-MIO-16E-4 board.
Andy,
Unless you use a real time platform, getting extactly 1 ms loop rate
(or even less) is impossible. It starts getting troublesome at about
0.1 Hz for standard operating systems.
I'd tackle your problem with "if i mod 10 == 0 then sleep 1 ms".
Of
course this is jerky by design.
HTH,
Johannes Nie?

Random delay between WHILE loop during acquisition from DAQ

I am working with the NI DAQ USB 6259.
My purpose is to acquire data from an analog voltage input. My problem is showed in the attached image and consists in a RANDOM time delay between the execution of two consecutive while loop that contains the acquisition and the writing operations.
If you observe the image attached, you can notice that samples are taken at regular interval (which I can specify) only within one loop, then between the instant of the last sample of one cycle and the one of the first sample of the next cycle, a random delay occurrs.
I attach also my block diagram which is very simple.
I am forced to use the option "N samples" in the daq assistant because if I use continuous acquisition an error is returned, I guess because my acquisition can last minutes.
It's like I were blind for a random duration between consecutive iterations of the while!
Do you know an alternative solution to avoid this problem or its solution?
Best regard,
Roberto Rodio
Attachments:
while loop delay.jpg ‏52 KB
block diagram.jpg ‏42 KB

Have you tried to execute this without the writing to the TDM file? I suspect that is where your delay is happening... So I propose you delete that from your block diagram... and execute your loop... if that works, you will need to move your file write to somewhere else in the process... possibly a parrallel loop... If not, consider stripping down the express VI you use for your data acquisition... The delay could be in that express... setting up, starting, acquiring and stopping the daq task... In which case, you can right click on it, say open diagram... or open vi or something similiar... LabVIEW will tell you that it must convert the VI, so OK (you can alway undo)... I am not sure what else you have going on... so you may already be doing that... but that is the first two places I would look.
Paul <--Always Learning!!!
sense and simplicity.
Browse my sample VIs?

Writing a file for prescribed amount of time in a while loop after the triggering condition is met

Hello Guys,
I am trying to program an application in which if the trigger condition is met it should start to write the file.
I was able to do that, but if I want it to be written for certain amount of time, and once the trigger condition is met, it should continue to write the files for prescribed amount of time. I was not able to do this. The file name should also be updated accordingly.
I tried to with some options by keeping the creation of the file outside of the loop, if I do that then if the trigger condition is not met it will stop writing and I dont want that, as once the trigger condition is met it should be true thereafter.
So I cant keep any thing outside the while loop, bcaz then it checks the condition of the shift register for the trigger and I have it as a false constant.
I am attaching my application which is kind of mess and I have written in the application where I am having problems. For every iteration of while loop it makes a new file, and i dont want that, I want to write specific amount of time data to the each file.
Please take a look at my code and help me in solving the problem. Any insights and examples on how to do this thing will be a relief to me.
Thanks in advance.
Regards,
Nitin
Attachments:
PXI_4462_Sync_and_Stream_trigger.zip ‏192 KB

what i am saying is to keep track of how much data you have written and whenever you need to make a new file you make 1.
here is a vi that i just made that should show you. let me know if you need any help understanding it.
Attachments:
new file exemple.vi.zip ‏21 KB

Pause and restart while loop after defined time

Hello,
What I need is to find a way to run a while loop that is acquiring and analysing a movie, to pause this while loop for a time I specify, and re-run it after that time has passed.
I'm attaching a picture of the relevant parts of my VI. In the case structure of the "true" or "false", the program is checking, online, if the eye (my camera is focusing on the eye) is open above some threshold and for a certain duration of time. When "condition to start" is met, two things happen: one, the case structure changes to "false" and waits for some time; second, the loop of my state machine is triggered. Problem is, because I'm not really pausing my while loop (it's still running even when it's the "false" case), my state machine runs really slowly - for example, I have a part of video acquisition in my state machine, and saving the frames to avi takes forever.
Does anyone have any idea of how I could stop the while loop for x time?
Thanks in advance!
Attachments:
help_pauseWhileLoop.png ‏112 KB

Hi,
I'm attaching (hopefully) better pics, if you still can't see let me know and I'll attach the code. About the frame saving and acquistion, I'm already doing that in a separate loop - you can't see my entire code in the pics, but what I have is a state machine that works as a producer loop and then a consumer loop, where video acquisition is happening. Now I'm working on a third loop (the one in the picture), that starts before the others and where I don't even want to save the movies - I just want it to check, online, if the condition is met (e g, the eye is open for a specified time) and if so, start the state machine and stop running, until the state machine has finished running. Then do the same, after waiting a specified time. I know that the problem is that the while loop keeps running after triggering the state machine, because if I remove that part and trigger it manually, the VI runs just fine and really fast. So how can I run, stop and restart the while loop?
Attachments:
help_pauseWhileLoop1.png ‏56 KB
help_pauseWhileLoop2.png ‏32 KB

While loop halted

Hello Folk,
I am developing an application which acquires data at 1 ms and store it to TDMS file. I have two seperate loop for acquisition and data writing. I set starting of acquisition on trigger pulse so while loop halts untill my system is triggered and resume on trigger pulse. Now that writing into TDMS file is slower than acquisition, I queue acquired data and dequeue it in another loop.
Here my problem comes,
As of faster acquisiton, for 600 seconds data acquisition my file is written with only 195 seconds data. The rest of data is in queue. As soon as the stop trigger comes my acquisition loop halts and with it my writing loop halts too. It is not being possible for me to write another 405 seconds data in to file though my program is running.
Is there any way that my writing loop never halts? I havenot configure anything for my writing loop to halt however the dequeue reference of my writing loop is the same as queue reference of acquistion loop.
Your help will be truly appreciated.
Thank you,
CLAD
Passionate for LabVIEW

Hello,
I designed this code for RT and that is why I used timed loop and dint put any condition to stop the loop. I m not sure am I right or not on this.
Answers to your other questions are below,
Only latest packages are missing and I removed that sequence.
Can you please put some more sense into me for well designed RT code??
One more thing I would like to ask is there any way to write the data faster,? I meant as soon as the data queued up it should be written into file.
Norbert_B wrote:
Several things to consider:
- Without seeing the complete code (VI), we can only guess about things
- You use nested case structures which rely on shared variables to enqueue data. I doubt that you enqueue the amount of data you *think* you enqueue
- Have you ever checked the iterators for the loops? For the enqueuer, you should create a custom iterator to count the enqueues you are performing (seems that you are already counting this, but not "using" it)
- Which "packages" are "missing"? Only the latest? Some "in between"?
- Why do you use a timed loop as producer?
- Why are both loops running without the option to stop? Is that a program running on RT, please learn how to desing code for RT.... (as your code is obviously not designed for RT)
- Why all those sequence structures? Please remove them
All in all, i currently assume that the VI is working "perfect" as it only does what your code tells it to do. If that is the same that you *want* it to do.....is the question.
Norbert
Norbert_B wrote:
Several things to consider:
- Without seeing the complete code (VI), we can only guess about things
- You use nested case structures which rely on shared variables to enqueue data. I doubt that you enqueue the amount of data you *think* you enqueue
- Have you ever checked the iterators for the loops? For the enqueuer, you should create a custom iterator to count the enqueues you are performing (seems that you are already counting this, but not "using" it)
- Which "packages" are "missing"? Only the latest? Some "in between"?
- Why do you use a timed loop as producer?
- Why are both loops running without the option to stop? Is that a program running on RT, please learn how to desing code for RT.... (as your code is obviously not designed for RT)
- Why all those sequence structures? Please remove them
All in all, i currently assume that the VI is working "perfect" as it only does what your code tells it to do. If that is the same that you *want* it to do.....is the question.
Norbert
Thanks for your concern
CLAD
Passionate for LabVIEW

What is the maximum size of indexed array that can be created during execution of while loop?

Hello,
I am using a ring acquisition to take in images. If i write them as files in the loop, it slows down the acquisition unacceptably. Therefore i am converting image to array and storing the array until the acquisition is complete and then reading the array and converting back to image to save. The program sometimes runs out of memory (after a couple of minutes). Can anyone think of a way where i can store the array/images within the execution (without losing image information), without slowing it down and to avoid this memory problem?
I have included the VI.
Thanks in advance for any help or advice.
kindest regards,
FraserD
Attachments:
LL_Ring_in_IMAQ_8_bit_array_then_write_as_png.vi ‏94 KB

When you build the array of pictures you do it using auto-indexing out of a while loop. That means that memory is aquired for a copy of the previous picture array and the array is rebuilt on every iteration, this is slow and requires a lot of extra memory.
If you want to speed things up try initializing a shift register with a 3D array of a size that will be able to hold a certain number of pictures, then replace the "pages" as new pictures are aquired, replace operations do not require copying of the previous array and will thus be much much faster. The difference is exeptional when dealing with large arrays/amounts of data.
Now, the shift register buffer could be built into a functional global, and you can add a push/pop logic to it so that you can have a p
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MTO

LED blinking in while loop

Hello
My application involves reading data off of a serial port at 26Hz. I am parsing this data in real time and writing statistics to file. I want to have an LED blink each time a file is written (I have a files being written in the following intervals: 1sec, 3sec, 15sec, 60sec, 10min). My problem is that the LED only stays illuminated for the single iteration, which is dictated by the speed I am reading from the serial port. Is there a clever way to have the LED flash for a standard .5 sec without creating timing issues?
Cheers!
CLA, CLED, CTD,CPI, LabVIEW Champion
Platinum Alliance Partner
Senior Engineer
Using LV 2013, 2012
Don't forget Kudos for Good Answers, and Mark a solution if your problem is solved.

Thank you for the reply, I create a new set of five files at midnight and append to them throughout the day at the given interval. As I understand it the property node causes the LED to blink at a set interval. I am looking to have the LED blink at the predetermined interval (1sec, 3sec, 15sec...) and stay illuminated for 0.5sec each time it blinks. I have the triggering for the blinking worked out so that it blinks when I want it to, the problem is that it is in a while loop that is executing very quickly and so the LED doesnt stay illuminated for very long when it does blink. I hope that this helps.
Cheers!
CLA, CLED, CTD,CPI, LabVIEW Champion
Platinum Alliance Partner
Senior Engineer
Using LV 2013, 2012
Don't forget Kudos for Good Answers, and Mark a solution if your problem is solved.

While loop doing AO/AI ... Performance?

Hi!
I have been trying to get a VI to do concurrent Analog
data in and out and both the input and output rates and
waveforms can change while the VI is running. My problem
is this:
(a) If I try putting the read and write operations in
separate while loops, one or the other loop will
die in a buffer over/underrun.
(b) If I put both into the same loop, then this works
but I am limited in the choice of data-rate parameters
because eventually one or the other DAQ VI will take
too long.
At this point I have only one loop and the buffers are big
enough to hold 10 iteration. Every time one of the loops
dies I reset it. Still this seems awkward. Is there a
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he
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Rudolf

Ok, I knew that ocurences did something useful but I am
still a bit confused:
* Can you set an occurrence for an output event. None
of the examples I've seen say so but it looks like
it should work
* How do occurrences actually help with the "hanging"
problem. Does the compiler see the occurrence in
a loop and change the wait parameters?
I looked at devzone but most of the stuff I found there,
even the promising looking stuff was all about
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Rudolf
JB wrote:
: Once in the read function, the program "hangs" until the number of
: data points is in the buffer. The same applies to the write function.
: This means that most of the time, your program is waiting.
: To sol
ve this problem, you must use DAQ occurrences (--> hardware
: events).
: For examples for using daq occurrences, type "daq occurrence" in the
: search of the LabVIEW help or even better, at
: http://zone.ni.com/devzone/devzoneweb.nsf
: Hope this helps

Why writes LabVIEW only every 2 seconds the measured Value to a Excel (In a while loop with 100 ms tact)?

Hi everybody,
I use the myDAQ to measure speed, ampere, and voltage of a battery driven motor. (For Current measurement, i use a Sensor which outputs a 0-10 V signal). I placed all DAQ-Assitants in a while loop with a [Wait until next ms multiple] clock and set a value of 100 ms. I thougt, Labview will now write into my text file 10 times a second all values. In fact, as you can see in the attached text file, Labview only writes in a unsteady interval of 1-2 seconds a value, which is too less.
The question: Did I do anything wrong, how can you create VI that writes you lets say 10 values a second into text file? Or is simply the DigitalMultimeter input of the myDAQ not able to sample a rate of 10 Hz? I couldn´t find any information in the specification handbook about the sample rate of the DMM?
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Attachments:
Measure Speed+Current+Voltage into Excel.vi ‏175 KB
Test7.txt ‏1 KB

File I/O is not very efficient. I recommend that you do you file logging in a parallel task. Have one task do your data acquision. This task would then pass the data to be logged to the logging task via a queue. That way your file operations do not impact your data acquision. Also, express VIs are not very efficient. You would be better off accessing that directly using the DAQ VIs. The express VIs contain lots of steps that do not need to be done every time you call it such as initializing the device.
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot

Problem with DAQ in while loop and Graphs

Hello,
I'm new here so I apologize if I posted this on the wrong board
This is my "situation":
I need to make a simple PID controller which takes information (process variable) from an outside source (a NI's DAC connected through the USB port ) which is accomplished using NI-DAQ as an input, and the PID's output goes to the second NI-DAQ which is also connected using DAC to an actuator which in my case regulates the air pressure. (VI attached)
My problem is the following.
Both of the NI-DAQ I placed using DAQ Assist, require to be in a while loop.
-If I place them in separate loops, I have the problem of passing information between the Input NI-DAQ and the PID, and also between the PID and the Output NI-DAQ.
-If I place them both in one big loop, an error occurs saying that the selected buffer size is too small (Error -200609).
The timing settings for the DAQ's N samples, 100 samples to read at the rate of 1k (I also tried with Continuous samples and many different combinations of Samples to Read an Rate but without success).
Should I wire them with the same dt(s)?
The other thing I need to do (I'm also writing it here in order not to open new topics) is show the following 3 signals on a Graph (process variable (dynamic data type)(range 4mA - 20mA), PID output (double)(range 4mA - 20mA), and the Set Point (double)(range 0 to inf))
Firstly, is it possible to show the first two on a scale from 0 to 100 without changing the PID's output which needs to be 4-20?
Secondly, which graph should I use if I have different data types? (I tried the Waveform Chart, and succeeded in showing the first two; the third just messes everything up)
I would also have to make a legend explaining which signal is which (I see that this is possible with the Mixed Signal Graph).
I know this is probably too much to ask, but I'd be grateful for any help
Thank you in advance
Attachments:
PID while.vi ‏100 KB

My problem is the following. Both of the NI-DAQ I placed using DAQ Assist, require to be in a while loop.
-If
I place them in separate loops, I have the problem of passing
information between the Input NI-DAQ and the PID, and also between the
PID and the Output NI-DAQ.
This is the best option---Use QUEUE or Functional global or something else to tranfer the data to and fro
How do I make that QUEUE or Functional global?
-If I place them both in one big loop, an error occurs saying that the selected buffer size is too small (Error -200609).
Have
you tried increasing the buffer? Is the acquisition happening
parallelly (means to say the first DAQ not wired (error terminal) to
second DAQ)
Well the buffer is, at least how I understood it, the option Number of Samples when in Continuous Samples mode. Concerning the parallel acquisition, do you mean I should wire the error ports of both of the DAQs?

Triggered finite acquisition in a while loop - speed limit ? (newbi)

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