data logging using LVM - file

[Balaji_DP]

hello,

           im doing datalogging with hardware of scxi - 1520 and NI - PXI - 4472B datas. As per my client requirement, datalogging to do for dynamic data. i setup my programm as for above datas are 10k samples with 8 channel each and all datas are to be logg using "write Labview measurements file.vi". when i  start datalogg around  within 1min the file size will be a 10mb or more. so that, using"read labview measurement file.vi" i cant read the datas, cause the system getting hanked or slow down.

i want to datalogg 10k samples each 8 channels using above hardware, suggest me  which VI i can use.

reply me as soon as possible..... 

Regards,

Balaji DP

Application Engineer,

Reckers Automation Pvt., Ltd.,

New Delhi

[MissyS]

Hi Balaji,

You can have your data written to multiple files, using the Write to Measurement File VI. There is a radio button to select writing to multiple files instead a single file. Select the "Save to series of files (multiple files)" option. Then select the "Settings..." button. Here you can configure how the VI writes to the multiple files. In your case, you will want to select the condition to start a new file to be "When file exceeds limit" and choose a file size that is manageable to open. The default is 100 kB. I hope this helps!

Regards,

[Balaji_DP]

i already tried this method. but when im going to analysis mean that for FFT, power spectrum..

i need a contigious file for analysis.

another query's:  i have an daq card of 4472B (DAS). application has been developed for vibration analysis, got information from the daq manual  hardware is recommended for sound and vibration analysis, and its icp compatible.   my queri is, i have an "hammer"  which is an icp. can i configure with vibration transducer with hammer, im going to use 8 channel on one of the channel for hammer. but vibration and hammer configuration is different,  excitation also different , what can i do for?...........

i configured on labview with default settings for 7 channels and for 8th channel i made configure using "creat task with custom scale". why i did means because above two sensors are having different excitation value......

suggest me that is it possible to configure different sensors on same hardware?

Regards,

Balaji DP

Application Engineer,

Reckers Automation India Pvt., Ltd.,

New Delhi.

[MissyS]

Hi Balaji,

First, are you getting error messages when you try to load the entire file? How large is your file? Are you saving for a minute? Or is it longer? Can you open these files in another application (such as Notepad, Microsoft Excel, etc)? This would check to see if there is anything wrong with the file.

One thing to consider trying would be putting each channel into its own file. This way, you can have continuous data for each channel, but not have to load the entire data set. Another file system would be to save the data in the TDMS file format. This would be the easiest way to selectively load different channels into memory for data processing. See this tutorial.

As far as the other sensor with different characteristics, you should be able to add another channel to the task that contains the other channels. You will only be able to have one analog task per board running at a time, so the channels will have to be in the same task if you want them all read at the same time. I hope this helps!

Regards,

[DFGray]

You definitely want to use some sort of binary file format for this data logging.  LabVIEW 8.2 introduced the TDMS file format.  Using it is as easy as selecting it as the format in the write LVM express VI.  If you have an earlier version of LabVIEW, use NI-HWS.  It was introduced about LabVIEW 7.1 and is on your driver CD next to the computer based instruments.

Will you be analyzing your data in LabVIEW or an external program?  If you are using an external program, such as Excel, there are several plug-ins for TDMS available.  Check out the tutorial Reading and Writing TDM/TDMS Files.  NI-HWS is HDF5 based, so any external program which can read HDF5 can read NI-HWS.  The internal format is based on SCPI-DIF.

[Balaji_DP]

can you send some example programme to write and read as TDM file? right now im using LabVIEW 7.1, i have the 16 channel of datas with channel name , let assume each channel has an 10k sample . so i have to do data logging for 10 mins. its possible?

[DFGray]

TDM is not a suitable format for streaming data to disk (which is why TDMS was introduced in LV 8.2).  For LabVIEW 7.1, you should use NI-HWS.  If you have any of the computer based instruments installed (NI-SCOPE, NI-FGEN, NI-HSDIO), you already have it.  If not, it is in the same leaf in the installer tree on the Driver CD, or you can find it by going here.  It includes examples.  If you have any further trouble, let us know.

NI-HWS is capable of making files as large as your open disk space.  It can easily handle your data requirements.  It's write speed and file size are both essentially hardware limited and will scale with your computer capabilites.  At your data rates, you could probably do compression on-the-fly as well.

Message Edited by DFGray on 07-24-2007 07:48 AM

[Balaji_DP]

dear sir,

                    i down loaded the NI-SCOPE 2.1 Version and installed on my system. now tell me where i can find the vi for performing datalogging. i tried with storage vi. it showing error as "labview cannot read as tdm file". same error was happen before instalation of ni-scope

Regards,

Balaji DP

Application Engineer,

Reckers Automation India Pvt., Ltd.,

New Delhi

[DFGray]

NI-SCOPE 2.1 is a very old version.  I don't think it includes NI-HWS.  You can get the latest version of NI-SCOPE here.  It includes the latest NI-HWS drivers and supports LabVIEW 7.1.  It is unfortunately very large.  You can find NI-HWS on the Instrument I/O -> Instrument Drivers -> NI Hierarchical Waveform Storage palette.  The icon looks like a file folder with a tree structure in it.

Note that the location of NI-HWS on the palette has changed with various versions.  If it is installed, you can always find it by clicking the Search button at the top of the palette and entering HWS.

Let us know if you have further problems.

[S_Kanchap]

Hello,

I am successfuuly can read the file size of 250mb but now i have problem to show this data in "Table" indicator it became PC very slow and taking 4-5 minutes, please tell/advise me the solution!!!

Thanks