Q: No daylight saving in waveform chart

Hello,
I'm lost:
I have a large logfile (couple of years) and i wan't to display this
with labview. The times i use are labview timestamps (seconds since 1
januari 1904 0:00 utc). Problem is when i plot them in a chart it
displays them in my local time zone (amsterdam).
Is there a possibility to plot these data in an chart in UTC without
Daylight saving time? Most preferable without changing the timezone in
windows, but even then a UTC timezone without DST doesn't exist.
Any help???
many thankx,
Richard Dols

> I have never tested this and none of my customers called me about the
> following problem:
>
> What happens if the logging runs to the time where daylight saving is
> on or off? In March the local time jumps from 2:00 to 3:00 and in
> October it jumps from 3:00 to 2:00 giving two hours from 2:00A to
> 3:00A and from 2:00B to 3:00B. The numbering A and B is the rule used
> in Germany for the "document of birth" (Geburtsurkunde).
>
> Would this cause any confusion in the x-axis of a chart or graph?
>
Daylight savings in general causes confusion. I'm not certain that it
actually accomplishes anything positive anymore. But to your question,
what will happen when it changes?
This is all subject to change, either by us or the OS, but at t
he moment
LV uses OS libraries for turning a timestamp into a string. The current
behavior of those libraries is that all of the times, historical or
current will shift by one hour. It is very difficult for a computer to
determine whether the timestamp falls in an A or B period. Sure it can
be done, and I believe some Unix servers do it, but in general, everyone
does UTC internally and then uses the current time zone to adjust the
UTC, then determines whether DST is currently in effect, then turns that
number into a string.
I believe this means that if you are at work at 2:00 in the morning,
that you will get another 2:00 an hour later on the chart, but as soon
as the historical values scroll off the screen, all the previous values
will be labeled 12:00 1:00 2:00.
As I said, DST complicates everything and someone might change this
behavior in a future OS or a future LV.
Greg McKaskle

Similar Messages

Saving array data from a waveform chart

I am using a CRIO 9004 and a 9237 bridge module to measure some strains from strain gauges. I've got one timed loop that reads the DMA FIFO and puts the arrays of values (16 data points, 4 per channel) into a queue. In the consumer timed loop a For loop scales the binary data, auto indexes it into arrays, then the arrays are merged into a 2D array for the four channels displayed on a waveform chart . Everytime the consumer loop runs it indexes 4 data points (per channel) yet the waveform chart plots them in a consecutive manner and doesn't overwrite the previous four. If I convert the arrays to waveform arrays I don't see anything on the waveform chart.
If I pass the 2D array of data to a array indicator inside or outside the consumer loop I get only 16 data points. I want to save the information that appears on the waveform chart after the consumer loop but because I'm not using waveform data type I can't use the write waveforms to file vi. The waveform chart history buffer has been set to 195360.
Idealy we will run the four channels for 120 seconds charting the data and saving the data. The minimum data rate is 1613kS/s (403 per channel) The data can be saved after the loops have finished gathering and processing or while they are running. I noticed when I tried to write to TDMS it slowed the consumer down. Same thing if I use a shift register with the volume of data.
I suspect I'm not sending data to the chart in the correct manner ( usualy takes two attempts to "clear chart" using shortcut menu). I'm not too familiar with timed loops /producer consumer loops and just tried to put something together based on examples.
I've attached my host vi and front panel screenshot.

Hope they appear attached this time.
Attachments:
Basic DMA (Host).vi ‏444 KB
screenshot2.jpg ‏113 KB

Read from Measurement File to XY on Waveform Chart

Something pretty simple that is giving me a hell of a time right now.
I've got a .lvm here that has been saved from a DAQ and has one column of numbers starting from 0.0000 - 27.0000 in very small steps. The next column is amplitudes of the signal at the given time. Now, from this LVM file I'm starting a new vi and I want to read those values as X and Y and get them onto a waveform chart. As of right now I've tried hooking up "Read From Measurement File" and tried "Build Table" but that won't want to plug into a chart. Plugging the file directly into a chart causes two very different lines to show up but is no where close to what I'm looking for.
Any tips as to how to complete this?
Solved!
Go to Solution.

Tasty,
More often than not I find Express VIs to be more trouble than they're worth. Here's an example of reading tab delimited data in from an .txt and plotting Y values versus X values on a graph. Hope it helps.
Andrew
Andrew
Attachments:
ReadData.vi ‏14 KB
data.txt ‏1 KB

How to get the history(datapoints) of 32 waveform-charts which are in one cluster?

Thanks in advance. I would like to handle up to 32 waveform-charts by using a cluster. My problem is that the datapoints of their history has to be saved if a particular event occures. How can I get the character-node for the history of a waveform-chart inside the cluster?

I'm not certain what you are asking, but here's a suggestion. On the front panel, you can pop-up (right-click) on a waveform chart within a cluster and create a property-node (for the history), which can be manipulated as you desire on the diagram.

Waveform chart. Send data to Excel

I am monitoring the output voltage from a electronic circuit using LabView 7.1 and a DAQ card.
I have been able to view the output voltage using a Waveform Chart but i have been unsuccessful sending the data to a file. Only one data point gets saved each time.
I am using the "Write to Spreadsheet File .vi "
Could someone tell me what i am doing wrong?
Please see the program attached below.
Attachments:
Attempt 3.vi ‏26 KB

You can build a 1D array as your loop runs. Where your data exits the while loop, right click on the border and select 'Enable Index'.
If you want to save data continously, you need to move your 'Write to spreadsheet file' vi inside your while loop. As it is, only the last data point will be saved when you stop your loop.
You will also need to connect a control or constant to the file path input so that you do not get a file dialog every time your loop iterates. Further, connect a True constant to the 'append to file?' input so that you do not overwrite data.
Also, you may want to insert a wait period in your loop to allow other processes to run.Message Edited by DavidT on 04-27-2005 09:16 AM

Waveform chart data to file

dear sir,
iam getting eight different plots on waveform chart with system date and time. Now i want to store this eight values with system date and time in excel file as per specified time interval. it shoould be online because i don't want to stop my vi to save that data in file. Is it possible? If yes please help me.
thanking you
falgandha

Falgandha,
this can be done with ActiveX or just saving the data as spreadsheet file and then importing it to Excel.
If you like to know more about Excel and ActiveX, you should take a look into the ActiveX-examples of LabVIEW.
Saving data as spreadsheet file is available as examples as well, but maybe it is sufficient for you to use the "Write To Spreadsheet File.vi" from the file IO palette.
hope this helps,
Norbert B.
CEO: What exactly is stopping us from doing this?
Expert: Geometry
Marketing Manager: Just ignore it.

How to save data from a waveform chart to a file?

Hi! I have a question:how to save a real time data from a waveform chart? attachement is a example,how can i do to save the data from 0 second to 25 seconds to a file ?thanks!
Attachments:
example.vi ‏23 KB

You can use a property node to get the chart history as a array. Then you can write that data to the file. The data in the array in you example can also be writen to a file. If you only wnat a portion of the data to be saved, use the Array Subset function to get the part you want.
Lynn

Capture Wave Form from Waveform chart

Hello,
I am trying to capture the waveform from the waveform chart save it as an image.
The reason I am not saving the data is that we have a lot of test data and we do not want to plot hundreds of waveform again manually.
Does anyone know how to do it?
Thanks!
Solved!
Go to Solution.

Here's an easy way to save an image of the chart.
You can save only the chart as BMP, EPS, EMF or PICT with another method:
Jim
You're entirely bonkers. But I'll tell you a secret. All the best people are. ~ Alice

Save a waveform chart

Hello!
I am trying to save a Waveform chart into a file usin the Save waveform to a file.
I have been doing test with ramdom numbers in little programs and I was able to save then in waveforms, but I can not do the same in the program that recieves the serial data.
I have attachet my program.
I well be be gratefull if someone could help me. I am sure is a little thing what is wrong but I can not find it.
Thank you for your help.
Angel
Attachments:
cliente_grava.vi ‏112 KB

And unless you only want only the very last acquisition recorded, you're going to have to change your VI. When the while loop stops, all it passes to the write waveform is the very last 1D array captured. If you want all data saved, put the write inside the while so that with every iteration you append to the same file. Or, turn on indixing where the 1D array exits the while loop. This will create a 2D array of all data acquired. Also, using Write Waveforms to file is probably not the best function unless you are actually creating a waveform datatype with timing info. Write to Spreadsheet will write a 2D array of DBLs or create a waveform datatype inside the while loop

Waveform Chart only shows one channel or combines both channels?

Hi,
I have 2 analog input channels and data was obtained by sampling at 500Hz and saved into a text file.
Can any one take a look at my VI and tell me why I am either only getting one curve plotted in the Waveform Chart or it's simply a combination of both of my inputs?
Thanks.
hellolv
Attachments:
FILE_3.vi ‏48 KB

Hey hellolv!
The issue you are seeing is actually a pretty common one. For a chart to update two plots the input to that chart must be a 2D array. Basically this means that all you need to do is insert a Build Array function right before the chart. I coded a quick example that does this for two random numbers in a while loop.
If you have questions I might suggest that you implement this in LabVIEW. You could also check the Context Help (Ctrl+H) and the Charts.VI in the Example Finder (Help » Find Examples).
Hope this helps!
Andy F.
Message Edited by Andy F. on 05-01-2006 12:15 PM
Message Edited by Andy F. on 05-01-2006 12:15 PM
National Instruments
Attachments:
2DPlotWaveformChart.Png ‏5 KB

How to change output precision of DAQ to waveform chart and to spreadsheet

Refer vi attached, the DAQ connects to a waveform chart to a spreadsheet. I want to change the precision of the DAQ assistant output from 6 decimal places to 2 decimal places, but everywhere i searched on the DAQ assistant i cannot find a precision setting. Did i miss something? What is the elegant way to do this?
Thanks.
Message Edited by sunflower2772 on 09-08-2009 03:57 AM
Solved!
Go to Solution.
Attachments:
all-instrumentasst 5 sep header change.vi ‏220 KB

Hi sunflower,
this seems related to this question...
Why do you want to change the output of the DAQ assistent?
Shouldn't you change the precision of the spreadsheet creation? To do so you simply have to give some parameters to the "to string conversion" functions...
Apart from file saving all other display precision settings are just cosmetics of the indicators!
Message Edited by GerdW on 09-08-2009 11:07 AM
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

How to save the waveform chart information

I am attaching a VI which recordes the power and wavelength from a ILX lightwave power meter. I had added waveform chart to the program to record the values of quatities with respect to time. Please kindly help me to read the quantities on time with saving the values from initial time to final time. I I use shift registers with a built array in the while loop , will it retains the past values?

I had added waveform chart to the program to record the values of quatities with respect to time.
Wrong. Charts don't display values with respect to time!
Hey Gerd,
I don't quite understand. If I wire a waveforme to a waveform chart it stores an processes data as waveform i.e. t0,dt and [y]. This, to me is in respect ot time.
If you meant, though, that it doesn't do that in his case, I very much agree with you.
As for the free tutorials:
3 Hour Introduction
6 Hour Introduction
LabVEW Basics
Self Paced training for students
Self Paced training beginner to advanced, SSP Required
LabVIEW Wiki on Training
Learning NI
Getting Started with NI Products

How can i display Waveform chart in a subpanel using Vi templates.

Hi All
I am new to Labview hence need some help. I am trying to develop an application which reads some data from a Wireless Sensor Network (WSN). The WSN consists of base station connected to the USB port which recieves data from other sensor nodes. The data comes in a certain format. Node name, temperature reading, humidity reading etc. I want to read the data from the serial port and based on the Node name, i want to display the information for each node in s separate window or subpanel etc. So if a new node is detected then a new window is created for that node. Since all the nodes have the same sensors on board i only need a one template. I can read the data using the serial port, parse the data to detect which node it is and also what the sensor readings are. I have created a template VI for the sensor node. I am having problems in displaying the template VIs in a subpanel. I can succesfully display a Waveform graph in the subpanel but i am having problems in displaying a waveform chart in the subpanel. I can see the actual waveform chart in the subpanel, but i cannot see the plot. Would be greatful if someone could point out what i am doing wrong here.
Many Thanks
Raza
Solved!
Go to Solution.
Attachments:
template_graph.vi ‏16 KB
graph_template.vit ‏11 KB

Hi All
I think i have solved the problem. It seems like i was running the Vi in a loop. I have taken the Run Vi outside the while lopp and this works fine. Also i need to close the reference at the end.
Raza

How can i print out the waveform chart?

hello everybody,
how can i print out the "waveform chart". can i do it just push the button. ( example; stop button is stop the program etc..)
i checked the NI examples but i can't understand. i'm new to the Labview.
pls help me.
i added the my program
look forward your reply
regards from turkey...
Message Edited by hknmkt on 05-29-2008 04:15 AM
Attachments:
29.05.2008_11.vi ‏37 KB

hi jim,
i tried the program but it's not running. When i run the program, it's print out without run the program
i added the printed file.
look forward your reply
hakan
Attachments:
error8.JPG ‏8 KB

Display Data on waveform chart or XY graph over a long period of time

Display Data on waveform chart or XY graph over a long period of time
Can anyone help?
I am acquiring data from an Ni DAQ card with the following parameters - sample rate = 12800, number of samples = 4096. I want to extract order information so as to track changes in the amplitudes of certain frequency harmonics. So I use the sound and vibration toolkit to extract this information as shown in the attached Vi. I will like to plot the resulting amplitudes against real-time starting at the time the Vi was run. I really want the display to show these changes over long periods (eg. days, months and even years).
Problem.
I have tried to plot the Y component of the resulting magnitude for a given order on a waveform chart. My choice of the waveform chart is because I also want to display alarm limits (using the mask and limit vi) (I can't have these lines displayed on an XY graph plot). I tried adjusting the scale offset using the property node and setting the offset to current time. However, the display on the X-axis can only show a span of 2 minutes as will be seen when you run the attached vi. I want the time display on the x-axis to be over a period of days, months and even years. Is there a way to set the maximum scale on the x-axis to be say a year or so in future.
I really want the display to be like the one in in the second attachment.
Attached is a sample VI created using an Ni USB 9234 DAQ card. Any card will do but I am only getting the signal from one channel for this example
I will appreciate any help that can be given to me.
Thanks
Attachments:
Real-Time Graph Display.vi ‏170 KB
Sampe screen1.doc ‏37 KB

Long term testing can be tricky- and we'l get into that later. Lets start with the basics that you have wrong.
The vi as you have constructed it has only one memory element, the chart history length (default is 1024.)
You can change the number of points the Chart will remember by Right-clicking the chart an select Chart History Length from the menu.
But for a long term test - and one where you want to REMEMBER the first value you need a memeory element that is independant of the application. Your PC WILL loose power or need to be rebooted eventually. Heck it might even need to be replaced! you really need to store your data in a file. Preferablly in a file that is backed-up on a regular basis so you don't lose every point of data if the PC dies. It realy hurts when you have to restart a 2yr test because you've lost the 18months of data you collected.
For an application like this I would seperate my "collection" and "Evaluation" operations.
Have one vi that takes the reading and writes it to a file at a configurable rate You may want 1reading per minute for seveal days then 1 per hour for a few weeks- then maybe only once or twice a week for the next couple of years since you are looking for LONG TERM stability. having too much data to evaluate can take a lot of digging to find the few things that interest you (but always take more that you think you need)
Have another utility that COPIES the files, reads them and displays the data you are interested in that day. The data you want to look at won't change over time HOWEVER, you WILL want to analize it in different ways depending on what the data trends look like. Having seperate routines for collection and display allows you to update the display style and analisys without even stopping the collection vi (much less editing the vi)
Jeff

Q: No daylight saving in waveform chart

Similar Messages

Maybe you are looking for