Datalogging with options to retrieve subset of log file based on date/time

Question

I would like to thank this forum for useful advice so far in completing my LabVIEW software.
I have a data logging challenge. I am supposed to log about 30 parameters every 5 seconds. Some of these parameters are digital (ON/OFF), some are values of speed (rpm) and others, an expression of a percentage (%). It should be possible in future to do a histogram or bar chart plot of some of the parameters, for a specific period range (say the last 5 minutes of a certain day). So in effect, do an extraction of a segment of the total log file.
My challenge is if I use text file, like the one in the attached VI, can it give functionality of retrieving data (while the VI is running) from the log file, based on a certain time range (i.e. retrieve a section of the log file based on a certain date/time range, on demand)?
The format in the text file is close to what I require, since it lists the time n one column and the other parameters on other columns to enable future histogram generation.
Thanks a lot, friends.
Solved!
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Attachments:
writer.vi ‏19 KB
time.txt ‏1 KB

Answer 1

Hey maxidivine,
Iv been playing round with your code and found that to perform the search that you require could be quite demanding to system resources when scaled to the size of your application I shall try and find a way to perform the search using .txt files but the there are some other options available. I recommend the use if TDMS files as the file format is a very efficient, manageable method of data-logging. The TDMS file format is designed to write and read measured data at a very high speed, while maintaining a hierarchical system of descriptive information.
Traditionally, TDMS was a National Instruments only file format – you could only read it using our products – LabVIEW/CVI/DIAdem. However, thanks to the popularity of the format, a bolt-on is now available for Excel, which allows you to directly open the .tdms files with Excel (see link).
National Instruments Technical Data Management Overview
http://zone.ni.com/devzone/cda/tut/p/id/3676
Introduction to LabVIEW TDM Streaming Vis
http://zone.ni.com/devzone/cda/tut/p/id/3539
VI-Based API for Writing TDMS Files
http://zone.ni.com/devzone/cda/tut/p/id/6471
TDM Excel Add-In Tool for Microsoft Excel User Guide
http://zone.ni.com/devzone/cda/tut/p/id/4906
TDM Excel Add-In for Microsoft Excel Download
http://zone.ni.com/devzone/cda/epd/p/id/2944
Troubleshooting the TDM Excel Add-In for Microsoft Excel 2000-2003
http://zone.ni.com/devzone/cda/tut/p/id/5874
Examples of the use of the TDMS API ship with LabVIEW. You will find them in HELP > find examples > fundamentals > File Input and Output. For you application, I would recommend the “Cont Acq&Graph Voltage - Write Data to File (TDMS).vi”.
Furthermore, if you require some help with DIAdem, I would recommend clicking "getting started" from the DIAdem splash screen. This opens a manual which discusses everything from data analysis to report generation. Also, if you have DIAdem 11 or above, there are tutorial videos which install with DIAdem. These are useful little tutorials, which discuss all the DIAdem fundamentals. You can access these by selecting a particular palette tab (eg. report, view, analysis...etc) and then clicking the tutorial button (shown as a film strip with a question mark) at the top of the group view.
Here are some more helpful DIAdem related resources for future reference.
Report Gen in DIAdem...
http://zone.ni.com/devzone/cda/tut/p/id/7379
DataPlugins: Supported Data Formats (ni.com/dataplugins)
http://zone.ni.com/devzone/cda/tut/p/id/4065
Hope this is helpful
Philip
Philip
Applications Engineer
National Instruments
UK Branch
===If this fixes your problem, mark as solution!===