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Raymond Tsang

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Everything posted by Raymond Tsang

  1. Hi LAVAs, I want to write a VI which "touches" a file. By "touch", I mean, to update the "last modified time" of a file without modifying its content. Using System Exec.vi, I made a simple VI (attached screenshots), but it doesn't do what it is supposed to do and return no error. I'm really puzzled . Any ideas? Ray
  2. Thanks for your advice. I've ordered a new card... PCIe 6535 with more on board memory (64k).
  3. QUOTE (jdunham @ Mar 3 2009, 07:50 AM) Thanks for your help, but it looks like it doesn't "double pulse". I'll play with for a while, or maybe just buy a new card, e.g. PCIe-6535, as a last resort. Ray
  4. Hi all, I'm using a PCI-6250 to pulse an LED at ~1kHz frequency. The pulse train looks like: 1 0 1 0 0 0 0 .... (all zeros until another pulse ~1ms later) Each bit is 100ns. Simple calculations tells me that I need to put 10k bits to the on board memory every 1ms which is more than the 2k bit limit on the board. (btw, I can't find any DIO board with on-board memory > 4k) If I do not use on board memory, LabVIEW complains about the data transfer is not fast enough. Since from the 4th bit onwards, the pattern is just plain zeros, is there a way to work around the memory limit problem? Thanks so much! Ray
  5. QUOTE (JamesP @ Feb 19 2009, 07:05 AM) Thanks for your suggestion, James! I tried to remove "clear task" and added "create task" with "auto cleanup" disabled. However, after the VI ended, the LED pulsing stopped, and when I started it again, LabVIEW complained about "resource being reserved" or sth like that. I'll keep trying... Ray
  6. Hi LAVAs, I encountered some problems when I'm trying to generate digital pulse trains to drive an LED via a PCI-6250 card. I want to implement it as two separate VIs: one starts pulsing the LED, the other stops it. (I tried to set "Continuous Samples" in DAQmx Timing.vi, but pulsing stops when the VI quits.) What now I can do is to generate one pulse train per run of the VI. (Screenshot attached) Any thoughts or suggestions? Ray
  7. QUOTE (giopper @ Aug 30 2008, 01:04 PM) Thanks! I'll try it tomorrow when i'm in lab. Never expected this post can become this long... I really appreciate the help from you guys!! Thankful Ray
  8. QUOTE (Götz Becker @ Aug 28 2008, 10:22 PM) Nice info! However, I guess I already know where exactly the memory leak is. It leaks whenever I convert a number to a string, which I cannot avoid. I guess it may be a bug in LabVIEW 8.5, although unlikely? Do you guys think the memory leak will go away when I compile it as an application? Ray
  9. QUOTE (normandinf @ Aug 23 2008, 07:44 AM) Which version of LV did you used? Can you try really running it for say 10-12 hours at 1Hz? I also had no problem in "accelerated" data taking. Really appreciate your help! Ray
  10. At last, I managed to capture a screenshot of the error.. It looks like a LabVIEW internal error... Any idea what this means? Ray
  11. QUOTE (normandinf @ Aug 23 2008, 06:44 AM) You don't have to be sorry! I really appreciate your help and of course your time and effort to try out my program! Now I have ruled out memory leak as the cause, because i don't see any more memory usage increase over time, using "profile performance and memory". I tried to run the program overnight again. The File IO error occurred, as always, around midnight 12am to 1am, which is a common time when people surf the net before going to sleep. So I suspect that maybe somebody is using VNC or other stuff connecting to the DAQ computer. As to whether the problem is system-specific, I will run a disk check... or what else do you think of? Desperate Ray
  12. QUOTE (normandinf @ Aug 23 2008, 06:53 AM) Many thanks! Here it is. This is the unsimplified version.
  13. QUOTE (neB @ Aug 22 2008, 10:05 PM) Thanks! Fascinating! Ray
  14. QUOTE (normandinf @ Aug 22 2008, 10:33 AM) Even if I unwire the graph, the leak is still there. In fact I found whenever I convert the cluster into a string for writing to file in "datalogger", i have a memory leak in the "main program" as seen in "profile performance and memory". I tried the following things: 1. Unbundle cluster, cluster to array, array to spreadsheet string 2. Unbundle cluster, format string 3. Cluster to array, array to spreadsheet string, concatenate strings 4. Number to fractional string, concatenate strings, and other permutations. All leaking... Is the passing of a cluster to the datalogger from the main program causing it? Ray the Leaker
  15. I think the problem i have is memory leak. I turned off (using a case structure wired with a FALSE) each component of the vi one by one and look at the "Profile performance and memory" found that, the leak comes from a "Cluster to Array". Now the problem is how to convert a cluster to an array without using "Cluster to Array"??? :headbang: Puzzled Ray
  16. QUOTE (Yair @ Aug 21 2008, 10:30 PM) The first didn't work, broken arrow. The second one is fine but this is just doing what i called "manipulations of a huge array". QUOTE (neB @ Aug 21 2008, 07:56 PM) Just use a Waveform Chart. When you present data as a Waveform datatype the chart looks at the "t0" value to determine where to plot the point. It allows you to plot multiple traces all having differnt "t0" values that are not periodic. Gotchas? Changing the number of plots shown will reset the chart. Present data that is earlier than data already plotted will reset chart. History is in units of WFs not data points (in the event you have WF's with multiple "y" values). Try it, you'll like it. Ben I'm not sure if i understand your suggestion correctly... Are you saying that I can treat individual points as separate plots with different t0? Afaik, there is only one t0 value for each plot, right? May I have a screenshot? Ray
  17. Thank you all for your comments! 1. I've checked that all the stuff hibernation/powersave/hdd turnoff/... are set to never. 2. My computer is not in a domain. 3. i didn't try to write to FP, but if i disable file io at all, it runs smoothly. In fact, I have just successfully run the vi overnight (20+ hours). But the computer has become very irresponsive. I checked the task manager to see that labview is using >110MB of RAM. Does it look like a memory leak or sth like that? Are there any memory leak checkers (like Valgrind) for LabVIEW? Ray
  18. QUOTE (mross @ Aug 21 2008, 06:36 AM) Thanks! Got it. But... because I'm taking data every second (or 0.1 sec), so every second, I have to pass a huge array through shift register, and put in one new entry. Is there a function in XY graph, where I can add a new point in every iteration? Ray
  19. QUOTE (giopper @ Aug 21 2008, 07:17 AM) Let me check the BIOS. I got a "Generic File IO error" from LV.
  20. I'm making a strip chart (actually consists of 3 overlaid strip charts) which has uneven time intervals between data points. That means the 1st and 2nd points may be separated by 2 sec, but the 2nd and 3rd by 1 sec, and so on. I have been exploring XY graphs, but it seems I can't overlay graphs. Any suggestions? Thanks in advance! Ray
  21. QUOTE (JiMM @ Aug 21 2008, 02:18 AM) OK. Thanks, JiMM! I will try to write the log to a text field on the front panel. (i suppose this is what you suggest, Ton?)
  22. QUOTE (Ton @ Aug 20 2008, 05:18 PM) Thanks for your reply! 1. this is the local drive. 2. what is FP? 3. i've checked the settings on the screensaver page. i guess that's the only place i can set hibernation policy, right? 4. no. when i came back to the computer, the user is still logged in.
  23. Hi LAVAs! I've a monitor program for some motors. Basically, it stops the motors when there's an error, and logs the status of the motor every 1 sec. When I ran it overnight, and checked the logfile next morning (while it was still running), I found that there is a 13 hour interval with no data recorded. Apparently, the data logging resumes after I come back. I've checked the hibernation/standby setting in Windows and it was set to be Always On. I've attached the screenshots of the simplified version of my programs here. Thanks in advance for any comments! Raymond
  24. Hi experts! I am trying to make a "data logger" and a "history viewer" for my instruments. Basically, the data logger record all the readings in a file in lvm format and then an operator of the intruments can view old data from the saved measurement files in a strip chart format. Now the problem is, I want to show the date and time information in the history viewer. Although the date and time are there in the header, but it seems there is no way to access them. Any ideas would be much appreciated! Thanks, Ray P.S. i thought of using xml, but since i've a have a huge data amount, so this would imply a huge array to be fed into the XML flattener. Any thoughts?
  25. Hi Siva, I'm also trying to capture snapshots from a webcam using LabVIEW. I tried to use your vi, but I've got the live image from the webcam only but not snapshots. An error (Error code: 3006) is returned by CopyToFileBMP, but this error disappears if I change the "Preferred execution system" to "User Interface" from "Same As Caller". I noticed that LabVIEW is not accessing the image file on disk. What could possibly the problem? Thanks! Raymond
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