Problems to use TimerEvent in While loop

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• problems of operation of two while loops in a VI

  Hi forum,

  I am developing a project for the acquisition of data continuously for two types of signals (voltage and temperature), each consisting of 20 channels. The sampling frequency is different so I used two call loops of different period to take account of the sampling frequency. It is within the VI that is deployed to the target device. On the host VI, I have two loops while put each containing a VI write_to_measurement express so I can connect the data to two different filepaths. However when I run the program, that a signal is registered correctly while the signal remains would have only one row of data. Looks like one of the while loop is only on the iteration while the other is running smoothly. This is an example of the famine of memory? How can I solve this problem! Any help greatly appreciated! Thank you!

  Vincent

  What asked Fan Ravens is why do you use static variable to stop the loop?  You do something remotely?  Simply use a local variable in your second while loop to stop him.  You need to change the action of the button stop, but that would be the way to do it.  Stop buttons are perfect for debugging and development, but generally I will use one other mechanism to stop the program runs outside the environment of LV.

• A specific problem with increment in a while loop

  Hello

  I'm pretty new to labview, I would be grateful if someone could help me out on this one.

  I am currently implementing a sweep of the tension, providing a starting Point, point stop and step size. I put in place using a point of loop, where a shift register adds on a step size to the starting point, and when the value is equal to the value of the stop loop breaks.

  The attached VI seems to work with integers for example Start 1, stop 10 and size of step 1.

  However, when I use a start value of 0, level of 0.1 and 1 stop, the loop never breaks. I tried the format & precision of edition but still can't make it work. Could someone please explain why this is happening.

  What I also noticed is that if equal to sign is replaced by a greater than or equal to, then the loop stops at 1.1 instead of 1. If I said the next START of 0, the increment of 0.1 and 0 STOP, the loop stops at 2.

  I have attached the VI (IncrementStepSizeWhileLoop.vi).

  Thank you very much.

  ranveerm

  You can calculate the number of necessary iterations from the parameters, so a loop IS more appropriate and you don't even have a comparison operation.

  

• Why used this simple while loop work?

  The main idea is to create a search feature on a form. I want to move to the next record, until I find what I'm looking for. Here is the code:

  These variables to get the numeric values of the NumericField5 and NumericField8. RawValue of NumericField5 will be below the NumericField8.

  strt var = NumericField5.rawValue;

  var end = NumericField8.rawValue;

  While variable rawValue strt is smaller that the variable end rawValue, move to the next record in the DataConnection.

  While (strt < end)

  {

  xfa.sourceSet.DataConnection.next ();

  STRT = NumericField5.rawValue;

  }

  When it works, evil created another loop of research when the variables range from end to beginning.
  I don't know why, acrobat crashes each time. Help, please!

  You can store the contents of the field before you enter the loop, then use a loop for wait until he changed. Then you would update the content stored with the new value so that the next time through await you on the right thing.

  Paul

• How to stop the While loop in the Structure of the event with the same button?

  

  Hello

  I have a problem. I want to use a single control to activate an event in a structure of the event and the same control to end a while loop in this case.

  It is possible to use 2 controls to do this, but I need to be alone.

  Thank you

  You should NEVER place while loops inside the case of the event, and it is never necessary to do. Think about it: all you have to do is spin the code. You can easily use the outside while loop for everything. Simply place the code of the loop internal (without the inner loop) inside the case of delay and manipulate the time-out period between a pending finished and the infinite (-1), depending on the State of the Boolean value.

  A very simple example (LV 8.0)

• Control of the event: how to stop the race while loop within a structure of the event

  Hello

  I have some problems with control of a while loop inside a structure of the event (see annex VI).

  I have 3 buttons (the "Start measurement, stop, exit the program"). When a measure is running, it should be possible to stop the measure by clicking on "Stop the measure", but it does not work.

  Someone at - it an idea?

  Thank you very much and best regards,

  Michael

  Hi Michael,

  create a process parallel to your measurement. You can use the design model "producer/consumer with vents. You'll find it with «File-> new...» ».

  Another possibility would be to remove the "lock frontpanel" sign, in the case of event start measurement.

  Mike

• How to extract an element of a table 1 d product within a while loop

  Dear all,

  IM new to labview. I got the task to create the program for the route of some settings in my lab. I created a program to interface sourcemeter keithley 2636b that will help me source voltages in a range and get the current and the resistance and ground them. I used a simple while loop for this. My problem is the following. I need t extract the nth element of the array created for resistance after each measure and store it in an array. I need to make a resistance measurement several times one after another and save the nth element each time these individual tables and push it into a buffer so that I can trace elements in the buffer against a setting (this is called a measure TLM). I tried several methods. Some nice guy / gal had posted a solution using the loop to retrieve an item. Its doesn't work don't not in my program I need to use a loop in my time loop and it gives is not the correct value. Kindly advice. IM in a lot of pain. Help!

  And indexing does not work?

  Why don't you check out 2D paintings and the bays of clusters and try to make your 'readable' with that code?

  Also there are many resources available online:

  Introduction of 3 hours
  Introduction of 6 hours
  Bases LabVEW
  Paced self-study for students
  Self Paced Training beginner to advanced, required SSP
  LabVIEW training Wiki
  OR learning
  Getting started with products OR

• To break out of the while loop (1)

  Hi all

  I have a simple question that if a callback to a command button function, I use a (bLoop) While
  loop, where bLoop is a boolean variable has the value TRUE, then how can I break up or out of this while loop by using a control on the façade, which released the while loop by setting bLoop = FALSE.

  I tried, but it didn't come out

  The problem here is that the CVI normally only runs a reminder at a time. While you are in snooze control, no treatment of GUI and subsequent calls to other reminders usually occurs.

  You can try the following approach-, but it's not really the best method:

  While (b_loop) {/ / within a reminder}

  ... / / Do your tight loop

  ProcessSystemEvents ();   Force the CVI to see if all the GUI needs maintenance controls

  }

  If you have a reminder of different control to erase the global b_loop, this packing approach might work for you.

  You must use this technique for very simple programs - it can quickly escape out of control and in the end upward in a mess if you're not careful. OR recommend that you use not ProcessSystemEvents() within a point of order.

  JR

• Case of Structure / while loop problems

  Hello

  I am trying to write a code that draws a random number whenever a key is pressed.  The chart must be a random number on the y axis and the number of times that the button is pressed on the x-axis.  I want to draw the last twenty random numbers.  I use a while loop and a box structure.  If the button is pressed, the case structure incruments the number of times where the button is pressed and generates a random number.  I'm using shift registers to track the last twenty numbers generated.  When the key not, registers to shift to day values incorrectly.  My code is associated with this issue.

  I know that the last value of the shift registers of wiring to the structure of the case will change the table across the last value when the button is not pressed.  I know what causes the problem, but I don't know how to fix it.  I would appreciate it if you have a look and give me some tips.

  Thanks in advance.

  Your problem is that the loop runs continuously and your values in the shift register are replaced when you do nothing.

  There are a few ways around this.  It would be simpler to use a Structure of the event.  Another option is to simply store your table in the shiftregister.  Use Rotate 1-d Array and replace a subset of table to update your chart.  It is a little more robust and easier to use than using the history of the shift register.

  But the absolute simplest, based only on what you told us, just use a graphic instead of a graph.  A graph keeps a history.  The length of the default history is 1024 samples, then you want to reduce that to 20.  Then you just wire your random number right in the chart, and everything is done for you.

  

• Table 1 d in the while loop problem

  Hello world

  I searched this problem in the forum, but seems only some positions quite didn't answer.

  I'm stuck by saving the data in a while loop.

  I have a while loop, within which there are two exits in each iteration, I want to add to a table, and then after the while loop is completed, I want to combine these two tables in a 2D array (since the release of them must be a pair in my case).

  I tried 'Build array' and 'transpose array' and 'write in spreadsheet' element set, which maintains concerns me is how simply to add the result in a 1 d table during each iteration, these 2 outputs are in digital format, which prevent to directly create a table for it.

  Any idea is appreciated,

  Thank you

  Chen Kunsheng

  Here are some other ways to insert.

  It may be useful

• How to use count imaq objects in a while loop?

  Hello, I am using objects IMAQ County and works well, but when I use a loop and I want to change the picture that I analyze to see results instantly, the search box, and the locations of the remains of the objects in the picture, even if I return to the original (for example at the threshold) values, objects of the location and the green rectangle remains there as the next image :

  

  This is the pattern I use:

  

  I used this same setup with the 3D IMAQ view and it works well, I change the values and changes in 3D view so do I.

  I use unduly the IMAQ dispose?

  Thank you very much for your help and comments.

  Bene

  The problem is due to the way works IMAQ Vision: the thread of the image contains a reference (handle), to the image, not the image itself. Means that once an image has been changed somewhere, the mods are propagated worldwide.

  The solution is simple: just add an IMAQ clear Overlay immediately upon entering the while loop (and add a small timer inside the loop).

  As an example, see the vi attached.

  

• Use of LabView delay in a while loop instead of use the inherent instrument of time loop.

  I have a lmg500 sez I use. It has the possibility of continuous measurement of data, with a cycle of user control loop (always using a while loop but the delay comes from the instrument). The problem is that the time of the loop is not constant. Can I use a very short time (100ms) as the cycle of the instrument of the time, but use a longer period in time loop collect data?

  I know that many instrument offers the same capabilities, so the issue is relevant to each of them.

  Thanks for any help

  You're not going to be accurate with Windows. The time between samples should be that you have programmed the instrument (i.e. the time between each value in the table 1 d) but the rate of the iteration of a while loop always will be the subject of a jig on a bone not real-time.

• Using 'while' loop or something like that

  Gurus,
  
  To do a selection online to compare a literal number. I thought I could use a "while loop" for this but get errors. Any other suggestions out there?
  
  
  

  while (select count(1) from mtl_cycle_count_entries where cycle_count_header_id = crec_purge_cc_by_hdr.cycle_count_header_id) > 0
    loop
       ...
  end loop;

  Thank you.
  
  Points for correct or helpful answers.

  PL/SQL is two other languages. PL and SQL - integrated at the level of the source code. It is not T - SQL where the SQL language have been extended with additional procedures and conditional structures and treatment orders.

  If you can not run a SQL and compare that with a PL variable by using a condition WHILE . The next type of conditional processing is necessary.

  loop
     select
        count(1) into someVar
     from mtl_cycle_count_entries where cycle_count_header_id = crec_purge_cc_by_hdr.cycle_count_header_id;
  
      exit when someVar <= 0;
  
     .. code ..
  
  end loop;
  

  Select ugly even if - as the part must be modular in function.

  So put this selection in a function, will allow you to do what follows - as you expected:

  while someFunction > 0 loop
    .. code ..
  end loop;
  

  Points for correct or helpful answers.

  Oh please... do you honestly think that I spend my free time here, for points? The points are useless and meaningless. It can't buy you a beer. He does not buy respect you. It would be silly to put on a RESUME.

  It is therefore a bit insulting to have points restless as a carrot to meet a problem here. Some of us don't never ask for to the points system. Some of us do not think it helps anyway to the OTN forums - except to raise the noise level from those who think that forum points makes gurus and experts...

  Sorry for this rant - but the points thing is IMO the worst feature that has been added to the RTO since I've been around.

• How to increase code efficiency in a while loop (using PXI5105 for sampling outside signal digitalizer)

  Theoretically, we want the PXI-5105 (digitizer) have 302 record with each record has a 1260 sample (the save operation is inside a while loop) in approximately 30ms, however we have found that for each period (30ms), the PXI5105 only perform about 10 records. It is so wired. I wonder if the operations inside the while loop consume more time (for example 3MS), so that he cannot have 302 records even the PXI-5105 have 60 M/s speed of sampling. Is it true, you can find my labview code and if possible can you give me some suggestion in the most short time of operation of the loop.

  

  Please find attached labview code.

  Hi g_l_g_s,

  The digitizer PXI-5105 acquires data at the speed that you specify and stores the data in its memory embedded (up to 512 MB). The data is then sent to your computer when the Multi Fetch Cluster.vi is called. In VI that you posted, you are only fetch record during each while the loop iteration. If you want to retrieve 302 records you will need to specify 302 files in the horizontal Timing.vi to configure. For more information about scanners, you might find the DevZone, hereuseful.

  To determine the amount of time it takes for each while the loop iteration, you can consider using the structure of code in the example comparison community calendar, which is located here.

• To use or not to use: while loop?

  Being relatively new to LabVIEW and excited by the event programming Structure makes me think that a While loop should almost never be used.

  A While loop uses "polling" to see if a condition is fulfilled or not before you stop the execution, which eats memory. (No pun intended) while event Structures

  don't constantly gobble up CPU memory and waiting for something to happen, and then runs.

  Can someone give me a simple and good example of when it is appropriate to use a While loop? Do not hesitate to talk about certain situations more complicated, requiring a While loop

  which cannot really be addressed with the programming of the Structure of the event.

  While loops and structures of the event go hand in hand. You almost always want to place the structure of the event within a while loop. If you do not you will serve a single event. The while loop will allow you to repair all the events. It is important to note that when there is no event loop will not be doing anything. He will be inactive and essentially no time consume CPU. The structure of the event will have to wait for the next event.