Writing data time steps in LabView 7.0

I am using LabView 7 to input temperatures and write them to a .lvm file to be read by excel. The files that are written are only writing on 2 second intervals, but I need them at 1 second intervals...
Any ideas? I am using the express "write to data measurement file" vi. Thanks so much
Attachments:
another_attempt.vi ‏365 KB

I took a look at your VI and I am not sure what the problem is, however the VI you attached is not a complete working VI, so I may be looking at the wrong code.
Anyways you are collecting 1000 points at 1000pts/sec. Therefore the AI Aquire Waveform VI will take 1 second, and then after that you will then start to save data and do your analysis and then the anaolog output. So I would expect that your loop rate would be higher than 1 second, although I would be surprised if it is was exactly 2 seconds.

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When I run this VI "Waveform Time to Date Time String" in LabView 7.0 it will not pass decimals of seconds.

When I run this VI "Waveform Time to Date Time String" in LabView 7.0 it will not pass decimals of seconds. From decimals of inputline. If i disconnect the input to the subVI "Get Date/Time string vi" it will work propperly, it also doses if I reconnect it. I use LabViev 7.0.
So the problem i solved, but i dosent understund why it works in this way. Does it indicate other problems which will make my researchprogram unrelaible ?
Attachments:
Waveform_Time_to_Date_Time_String.vi ‏18 KB

Hello.
I checked your vi and it fails as you state.
It runs fine if: 1 Convert number to timestamp OR
2 Wire a constant to want seconds?
In labview 7.1, no problems.
I think is a job for NI engeniers.
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I use the LabVIEW (6.0.2 of course) Application builder to create a dll, and I cannot enter creation information, nor can I modify the date time property, which labVIEW does not properly set. I have tried to modify this information in Visual C++, but that destroys the dll because it wasn't compiled in VC++, and therefore isn't compatible.
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Dear Sir,
I was browsing through MSDN in trying to find the info you are looking for and I step into this next file:
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Nestor
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Getting correct Date/Time data in DIAdem 11 from LabView tdms data

I've got a handful of large tdms files (9-18 million data points) collected with LabView that I need to extract elements of, and export as a text file, with the time data as a string.
I'm using DataFileLoadSelect and the Register option and then DataBlCopy to bring in a chunk of data at a time, but I'm having to explicitly convert each time value from a LabView timebase (1/1/1904) to the DIAdem timebase (1/1/0000), not to mention the offset, before writing the date-time as a text string - this really slows the process down.
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Solved!
Go to Solution.

WfmToDateWfm works great, but there is a bug in the code if you want to use DataFileLoadRed and your starting point is not at the beginning of the file. There is a provision in WfmToDateWfm to handle the offset, but it's not hooked up:
OffStartTime = ChnPropValGet(Channel, "wf_start_offset") ChnDeltaTime = ChnPropValGet(Channel, "wf_increment")
RelStartTime = 24*3600*(Trunc(ChnStartTime) + 693958 + Abs(Frac(ChnStartTime)))
To make WfmToDateWfm work with an offset, simly add the variable OffStartTime to the RHS of RelStartTime
Eric

I need an app or software that records the date/time each time a write something and press enter. This needs to be quick so I can continue writing right after I press enter, and the date/time is inserted for each word. Does this sort of software exist?

I need an app or software that records the date/time each time a write something and press enter. This needs to be quick so I can continue writing right after I press enter, and the date/time is inserted for each word. Imagine a spreadsheet - each time a write something in a cell and press enter to go into the next cell, I need the app/software to automatically insert the corresponding dat and time. Does this sort of software exist?

No one here is going to do anything about it. Send feedback to Apple.
http://www.apple.com/feedback/ipad.html
Basic troubleshooting steps.
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DateAdd(interval,number,date) Visual Basic to LabVIEW Time Stamp add 18 months

Hi all,
I need to match Visual Basic Cmd = DateAdd("m", 18, Date()) which adds 18 months to today's date. When I use LabVIEW Time Stamp VI's at first I tried adding 1.5 years in seconds. but this did not match the VB generated method? What method do I use in LV to obtain the VB DateAdd("m", 18, Date())
Example 'Add one month to January 31, 2000
document.write(DateAdd("m",1,"31-Jan-00"))
Output:
2/29/2000

Well this is how you do it. However, it doesn't seem to work with the month. There was a thread about this problem not too long ago. If you overflow the month in the date/time rec cluster (so it is greater than 12), date/time to seconds returns 0. Every other element works fine. You can add 1000 to the day and it will figure it out just fine. When this bug is fixed, this will work. Also, it might only be a bug in recent versions. I'm on 8.5 and it doesn't work right.
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Message Edited by Marc A on 10-03-2007 03:56 PM
Attachments:
Example_BD.png ‏2 KB

Convert labview date/time to excel date/time

How do I convert the "seconds since 1904" from the function "Get Date/Time in Seconds" to an MS Excel date/time format? The application runs in the Solaris environment.

hi, I am not sure about Solaris env.
Maybe this will help in one way or another.
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ian.f
Sg/My
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Since LabVIEW 5.1... 7.1.1... 2009, 2010
依恩与LabVIEW
LVVILIB.blogspot.com
Attachments:
GetDatenTime_to_File.vi ‏48 KB

Wait Step - Delay in completion - Date/Time specified

Hi Experts,
I've requirement to wait till a specific date/time to reach. For this, I've created a custom method to find out the date/time according to the factory calendar. I'm using a wait statement with option 'Wait for Condition' and condition mentioned comparing the date/time with the system date and time.
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Are there LabView VI's for accessing and writing data to a CDF?

I am currently trying to develop a data acquisition system using LabView to acquire the data and to write the data to a file in NSSDC's Common Data Format (CDF). The CDF distribution (Windows 2000) comes with a precompiled dll of the CDF library of functions. Unfortunately, LabView crashes when I try to use the Call Library Function node. I am confident that it is not a function prototype error, but it may be that the CDF library is not thread-safe.
Has anyone developed VIs for writing and accessing data in CDF format?
Does anyone know how I can determine why the Call Library Function node causes LabView to crash when it uses a particular dll? There are a host of reasons given in the "Using External Co
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Thank you for your response. Actually, I have solved the problem by recompiling the source code for the CDF distribution using the Cygwin development environment. Cygwin provides a unix C compiler and linker which can create Windows executables and dlls. After modifying the makefiles that came with the CDF distribution I was able to build the dll and then use the Call Library Module to access the CDF functions.
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Writing data to spreadsheet with time stamp

Hi
I am in the process of making a data logger using FPGA DMA FIFOs to read analog inputs into a real time host vi. This vi then queues the data to a second, lower priority loop. It is my goal that at this stage the data will be written to a spreahseet somehow with a usec-accurate timestamp as the first column, and all relevent column headings etc
I have uploaded my project as a zip for your viewing.
Thank you all for your help!
Attachments:
HS DAQ.zip ‏656 KB
HS DAQ.zip ‏656 KB

Have you tried using the Get Date/Time in Seconds to return a timestamp for your data which you could then build into an array with your data? You could then write this data to a spreadsheet file if you like.
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How do I write to file at a discrete time step?

I'm writing some variables out to a binary file in real-time (xpos, ypos, elapsed time) with a while loop (see blockdiag.png). I'm using the time recorded by LabVIEW with an external devices clock to interpolate position values, before you ask, I don't have access to the external clock so interpolation is necessary after the data has been collected. Currently, the while loop is unabated and runs as fast as the CPU will let it. After I'm done collecting my data, I plotted up the elapsed time in MATLAB and noticed some very strange behavior, negative time (see clocks.png)!!!! The black data here is my external devices clock and the red data represents the elapsed time written out by LabVIEW. There are two instances in the vector that indicate a large negative step in time. This doesn't always happen and seems to occur somewhat spontaneously within the elapsed time vector.
Questions:
1) Has anyone seen this behavior before?
2) Would putting a Wait.vi in the while loop help? (I figured this would at least regularize the time step.)
3) Please help.
Much thanks, please don't judge my LabVIEW code (I'm sure there are better ways to do it, but it works and that is how I want it).
Adam
Solved!
Go to Solution.
Attachments:
blockdiag.png ‏302 KB
clocks.png ‏12 KB

AdamBlues wrote:
Much thanks, please don't judge my LabVIEW code (I'm sure there are better ways to do it, but it works and that is how I want it).
Adam
I just wanted to make a brief comment regarding the above statement. I would recommend that you be open to changes to your code. There are many VERY experienced LabVIEW developers on these forum and there is always an opportunity to learn and improve your code. Just because something works doesn't mean that the code can't be improved dramatically. You may find that being open to suggestion will result in you becoming a better programmer and that your applications are more stable, robust and easier to maintain. For example, more often that not you are much better office using a state machine to replace a flat sequence structure. Learn how to use dataflow properly and the need for sequence structures generally disappears. These are just a few things that can be done.
I guess my point is that it is a good idea to try and remain open above suggestions to improve or change your code.
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

How can I get a digital WDT that includes all samples, not just the one for the current time step...?

See block labeled ''digital data'' in my attachment for reference. Currently, only the digital data point for the current time step can be seen (it is deleted before the next one appears). However, I would like it display all the samples in the table like in the example found at this link under ''Digital Waveform Control'':
http://zone.ni.com/reference/en-XX/help/371361H-01/lvconcepts/fp_controls_indicators/
Many thanks for any suggestions! I am new to Labview, so I appreciate your help.
Solved!
Go to Solution.
Attachments:
myproject.vi ‏220 KB

Hey westerman111,
If you're looking to produce have your display include the solution information from previous solver steps, you will need to buffer the previous data. The way to implement this in a Control Design & Simulation Loop is using the Memory.vi found under Control Design & Simulation > Simulation > Utilities > Memory.vi. It will allow you to save previous information generated in the simulation environment for letter solution steps.
I've attached an example that should get you started in using the Memory.vi.
I would also make sure that what you're looking to accomplish is suitable for the Control & Simulation Loop. I know you mentioned you were new to LabVIEW so I wanted to make sure you were heading off in the right direction. Is there a particular reason why you are using the Control & Simulation Loop instead of a standard While or For Loop? The Control Design & Simulation loop is unique in that it calculates the solution of a dynamic system at a prescribed time step and ODE solver. It also provides the tools to interact with the model you are solving during execution. However, if you are simply looking to perform data acquisition and measurements (instead of dynamic model simulation) I would recommend using standard LabVIEW functions.
Here are some useful references for getting start with both LabVIEW and the Control Design and Simulation Module.
Tutorial: Getting Started with Simulation (Control Design and Simulation Module)
http://zone.ni.com/reference/en-XX/help/371894G-01/lvsimhowto/sim_h_gs/
Getting Started with LabVIEW
http://digital.ni.com/manuals.nsf/websearch/ba2fb433a7940e7a862579d40070cc2c
Tim A.
National Instruments
Attachments:
myproject_edit.vi ‏249 KB

Writing data to Microsoft SQL Server/Database

Hi All
I have written a program in LV ver 6.1 that carries out various functional tests and at each test gathers 3 data values. At the moment the data is gathered at each stage of the test and written in a concatenated string to a file that was opened at the start of the test routine. What I need to do is output the data such that it is compatable with SQL server (presumably in some form of table?). I have read previous posts but they recommed the ni database toolkit, which I do not have. Should I be using the XML vi to take the string of data or use the active x vi? I have read in other posts that you can manage without the ni database toolkit but would need to program a database structure. My knowledge of database development is nil and I wondered if there was a vi that could be used that would create tables that could be directly interpreted by MS SQL?
Labview Version 8.5
Labview Version 8.6
Labview Version 2013

I'm having trouble understanding exactly what you're doing, but I will try to explain a few things:
Ideally code written for database connectivity should not be included in my Labview code or problems could occur if my client changed his servers , database structure etc.
The code can be yours. If you do write it, just make sure to create subVIs, so that if the DB structure does change (something which is rare), you will only need to change the code inside the subVIs.
Microsoft SQL server is an intermediate piece of software that allows my Labview code to access the database without actually 'seeing' it. With my client using SQL server they can modify the way my Labview code sends data to their database if they decide to change their servers, database structure etc.
SQL Server is the DB management system. It holds all the tables, queries, etc. and is responsible for actually managing the DB itself.
What Dennis suggested was that the DB guy will write something known as a "stored procedure" and that you will call it.
In such a case, if the DB guy wanted to change something, he could just change the stored procedure and (if the change does not affect the interface), you do not have to change or rebuild your program. This is equivalent to the subVIs I described earlier, except in this case, the function is inside the DB itself.
Another version of this is creating a table with SQL commands and assigning a name for each command. You load the SQL command from the table by name and execute it. This allows for changing the SQL command inside the DB without changing your application.
ADO connectivity is used and the connection string is best located in the windows registry file. Presumably this option would give my client the most flexiblity? Is this the same thing as the .udl file?
Basically, the scheme is like this:
DB <-> DBMS <-> ODBC <-> ADO <-> Your Application
This may not be perfectly accurate, but the concept is basically this - in Windows, you talk to ANY database from ANY program using the same interface - you call ADO functions which will be responsible for getting to the DB you want and you use SQL to issue the commands, since the basic SQL commands are supported by all DBs.
To identify the DB, you use a connection string. This connection string can have all the data in it or it can point to an existing file (UDL or DSN) which holds the data pointing to the DB. Dennis suggested that when developing on your machine, you will use a file pointing to a local DB, but when deploying you will use a file of the same name which will point to the real DB. Your program will always go to the file and from there it will know which DB to go to.
The only time when this should really matter to the client is during configuration (for example, if the DB was moved to a different machine). All the client needs to do is edit the UDL file to point at the new location of the DB.
Again, the advantage of all this is that this is not part of your code and is done by programs which are built to handle it.
It is more efficient to use the Parameterized database technique such as the example given in the 'logging example parameterized'
I don't know how much this efficiency will be relevant in the speeds you need.
In any case, as I said, my own preference is to create functional subVIs - for example, a VI which will accept data in my format and will be responsible internally for converting that data and putting it into the necessary tables.
I have sent my client an outline of the data to be saved on their database, which at the moment comprises of 3 tables, the first has things like operators name, date, time, serial number etc ( 7 records, 3 fields) the second table has test reference (11 tests in total) with items such as fuel flow, fuel temp etc (11 records, 5 fields), Last table has 1 record and 6 fields. Unlike the Labview example each stage of the test can take up to 4 minutes to complete and if successfull the program moves on to the next stage of the test, saving the test results and if a PASS or FAIL occurred. The question I have is would it more efficient to save the results at the end of all of the tests or shold I connect to their database and save results as the tests progress?
I can't say I understand this, but my suggestion would be to let the client decide in what format they want the data, since they're the ones who want it. Work with the DB guy to decide exactly what data you need to put into the DB and where and then you can decide exactly which functions you need. As said, you might want to let the DB guy write some stored procedures which you can use to input the data.
Unless it's a large amount of data, writing to a DB is usually fairly quick (under a second). If it is relevant, my suggestion would be to write after each phase.
In any case, I suggest you go through some real DB tutorials (not LV related) and see if you can wrap your head about it. I know I don't particularly like designing DBs (or PID) any more than you do, but it's a skill worth having, and in some places, a DB makes things easy and practical.
Try to take over the world!

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

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!
Go to Solution.
Attachments:
writer.vi ‏19 KB
time.txt ‏1 KB

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!===

Writing data time steps in LabView 7.0

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