Best way to write waveforms to file

I'm reading 7 waveforms from DAQ at 20kHz sample rate and wish to write the data to a binary file [e.g. timeval ch1val ch2val....etc, in format timestamp sgl sgl sgl etc].
What is the easiest way to do this (without using the easy VIs)? The format of the file must be readable by other software - this is why I can't use the easy waveform VIs. The sgl and timestamp formats should be no trouble to read using e.g. MATLAB code.
The other consideration is that this writing to file must not interfere with the data acquisition.

To convert a floating-point value to it's binary equivalent all you have to do is use the flatten to string function. The tricky part is getting the application on the other end to recognize the format. As soon as you start writing binary data you have to start worrying about what processor the end user's machine is using because it makes a difference in how the bitstream is interpretted (bid-endian vs little-endian).
Remember also that to represent LV timestamps (which in the wider world are very nonstandard) you have to use either a double-precision float or a U32 number. In the Microsoft world a slightly more standard representation of time is the number of days since Midnight Jan 1 1900--a value which can be represented in a single-precision float.
T
here are also datalogging examples that demonstrate writing binary files--though those tend to use very low-level binary representations. They aren't even scaled to floats. This would provide the most compact storage since no number would be more than 2 bytes (16-bits), and the fastest too since you aren't taking the time to scale it in LV.
Mike...
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"... after all, He's not a tame lion..."
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Similar Messages

What's the best way for reading this binary file?

I've written a program that acquires data from a DAQmx card and writes it on a binary file (attached file and picture). The data that I'm acquiring comes from 8 channels, at 2.5MS/s for, at least, 5 seconds. What's the best way of reading this binary file, knowing that:
-I'll need it also on graphics (only after acquiring)
-I also need to see these values and use them later in Matlab.
I've tried the "Array to Spreadsheet String", but LabView goes out of memory (even if I don't use all of the 8 channels, but only 1).
LabView 8.6
Solved!
Go to Solution.
Attachments:
AcquireWrite02.vi ‏15 KB
myvi.jpg ‏55 KB

But my real problem, at least now, is how can I divide the information to get not only one graphic but eight?
I can read the file, but I get this (with only two channels):
So what I tried was, using a for loop, saving 250 elements in different arrays and then writing it to the .txt file. But it doesn't come right... I used 250 because that's what I got from the graphic: at each 250 points it plots the other channel.
Am I missing something here? How should I treat the information coming from the binary file, if not the way I'm doing?
(attached are the .vi files I'm using to save in the .txt format)
(EDITED. I just saw that I was dividing my graph's data in 4 just before plotting it... so It isn't 250 but 1000 elements for each channel... Still, the problem has not been solved)
Message Edited by Danigno on 11-17-2008 08:47 AM
Attachments:
mygraph.jpg ‏280 KB
Read Binary File and Save as txt - 2 channels - with SetFilePosition.vi ‏14 KB
Read Binary File and Save as txt - with SetFilePosition_b_save2files_with_array.vi ‏14 KB

Best way to read from a file

What would be the best way to read from a file. Which classes do I need to use?
I have to write a program, which reads data from a comma separated flat file, parse it and after inserting some busineess logic insert into a databse .
I will have to read the data line by line.
Any help????

I would use:
     public void readData()
          try
               data = new String[this.countRows("comp.txt")][];
               BufferedReader br = new BufferedReader(new FileReader("comp.txt"));
               for(int x = 0; x < data.length; x++)
                    StringTokenizer temp = new StringTokenizer(br.readLine(), "?");
                    data[x] = new String[temp.countTokens()];
                    for(int y = 0; y < data[x].length; y++)
                         data[x][y] = temp.nextToken();
          catch(Exception e)
               System.out.println(e.toString());
     private int countRows(String f)
          int t = 0;
          try
               BufferedReader brCountRows = new BufferedReader(new FileReader(f));
               while(brCountRows.readLine() != null)
                    t++;
          catch(Exception e)
               System.out.println(e.toString());
               return t;
          return t;
     }It works deliciously!

How to view waveforms in DIAdem that were saved in Labview using "write waveforms to file" VI

I'm new to DIAdem but would appreciate any help to my question.
I seem to be having a little trouble but how do I view waveforms
in DIAdem that were saved in Labview using "write waveforms to file" VI??
tks, Terry

Hello,
There are several ways to write waveform data from LabVIEW so it can be accessed from DIAdem. Two of the easiest ways are to use either .lvm files or .tdm files. You can write .lvm files using the Write LabVIEW Measurement File.vi which is located in the File I/O palette. You can write .tdm files by using the storage VIs which are located in the File I/O >> Storage palette. So, I would recommend using either of these file formats if you are developing a new application since these can be loaded into DIAdem directly.
If you are interested in loading files that where already created from the Write Waveforms to File.vi, I am wondering what file type you are using. For example are you saving your files as .dat or .txt with your Write Waveforms to File.vi? Feel free to reply to this thread with this information and I would be glad to help you out.
Regards,
Kevin L.
Applications Engineer
National Instruments

What is the best way to keep my personal files stored in iCloud separate from my work-related files?

What is the best way to keep my personal files stored in iCloud separate from my work-related files? It seems that I'm not allowed to link my iPad mini and my work iMac using two different accounts, so I'm wondering how to make my single personal account work for both, while keeping personal vs work files reasonably separated.
Thanks for any suggestions.

Is it possible for you to upgrade your account to iCloud Drive? That would mean, all Macs upgraded to Yosemite, and all mobile devices to iOS8?
See: iCloud Drive FAQ and iCloud: About using iWork for iOS and iCloud
In iCloud Drive you could create two separate custom folders, one for work documents and one for private documents and organize your documents there. Don't use the app specific folders (Keynote, Pages, Numbers, ...) , because you can only create one level of folders inside these folders.

Best way to write SELECT statement

Hi,
I am selecting fields from one table, and need to use two fields on that table to look up additional fields in two other tables.
I do not want to use a VIEW to do this.
I need to keep all records in the original selection, yet I've been told that it's not good practice to use LEFT OUTER joins. What I really need to do is multiple LEFT OUTER joins.
What is the best way to write this? Please reply with actual code.
I could use 3 internal tables, where the second 2 use "FOR ALL ENTRIES" to obtain the additional data. But then how do I append the 2 internal tables back to the first? I've been told it's bad practice to use nested loops as well.
Thanks.

Hi,
in your case having 2 internal table to update the one internal tables.
do the following steps:
*get the records from tables
sort: itab1 by key field, "Sorting by key is very important
      itab2 by key field. "Same key which is used for where condition is used here
loop at itab1 into wa_tab1.
read itab2 into wa_tab2     " This sets the sy-tabix
       with key key field = wa_tab1-key field
       binary search.
if sy-subrc = 0.              "Does not enter the inner loop
    v_kna1_index = sy-tabix.
    loop at itab2 into wa_tab2 from v_kna1_index. "Avoiding Where clause
      if wa_tab2-keyfield <> wa_tab1-key field. "This checks whether to exit out of loop
        exit.
      endif.
****** Your Actual logic within inner loop ******
   endloop. "itab2 Loop
endif.
endloop. " itab1 Loop
Refer the link also you can get idea about the Parallel Cursor - Loop Processing.
http://wiki.sdn.sap.com/wiki/display/Snippets/CopyofABAPCodeforParallelCursor-Loop+Processing
Regards,
Dhina..

Best way to write this sql ?

Please let me know best way to write this SQL.
select col1, count(*)
from TableA
group by col1
having count(*) =
(select max(vals)
from
select col1, count(*) as vals
from TableA
group by col1
having count(*) > 1
)

post EXPLAIN PLAN
SELECT col1,
       COUNT(*)
FROM   tablea
GROUP BY col1
HAVING COUNT(*) = (SELECT MAX(vals)
                   FROM   (SELECT col1,
                                  COUNT(*) AS vals
                           FROM   tablea
                           GROUP BY col1
                           HAVING COUNT(*) > 1))

What is a best way to write SQL ?

Sample Case
drop table t;
drop table b;
create table t ( a varchar2(4), b number, c varchar2(1));
insert into t values ('A00', 10, 'R');
insert into t values ('A01', 11, 'R');
insert into t values ('A02', 12, 'R');
insert into t values ('A03', 13, 'R');
insert into t values ('A00', 10, 'P');
insert into t values ('A01', 11, 'P');
insert into t values ('A02', 12, 'P');
insert into t values ('A03', 13, 'P');
commit;
create table b ( j varchar(4), k varchar2(1), l varchar2(5), m number(3), n varchar2(5), o number(3));
insert into b values ('A00', 'P', 'FIXED', 100, 'FLOAT', 60);
insert into b values ('A01', 'P', 'FIXED', 101, 'FIXED', 30);
insert into b values ('A02', 'R', 'FLOAT', 45, 'FLOAT', 72);
insert into b values ('A03', 'R', 'FIXED', 55, 'FLOAT', 53);
commit;
10:19:13 SQL> select * from t;
A B C
A00 10 R
A01 11 R
A02 12 R
A03 13 R
A00 10 P
A01 11 P
A02 12 P
A03 13 P
8 rows selected.
10:19:19 SQL> select * from b;
J K L M N O
A00 P FIXED 100 FLOAT 60
A01 P FIXED 101 FIXED 30
A02 R FLOAT 45 FLOAT 72
A03 R FIXED 55 FLOAT 53
1/     In table t each reference having 2 records one with P another is with R
2/     In table b each refrence merged into single record and there are many records which are not existing in table t
3/      both t and j tables can be joined using a = j
4/     If from table t for a reference indicator is 'P' then if have to pick up l and m columns, if it is 'R' then I have to pick up n and o columns
5/     I want output in following format
A00     P     FIXED          100
A00     R     FLOAT          60
A01     P     FIXED          101
A01     R     FIXED          30
A02     P     FLOAT          72
A02     R     FLOAT          45
A03     P     FLOAT          53
A03     R     FIXED          55
6/     Above example is a sample ouput, In above example I have picked up only l,m,n,o columns, but in real example there are many columns ( around 40 ) to be selected. ( using "case when" may not be practical )
Kindly suggest me what is a best way to write SQL ?
thanks & regards
pjp

Is this?
select b.j,t.c as k,decode(t.c,'P',l,n) as l,decode(t.c,'P',m,o) as m
from t,b
where t.a=b.j
order by j,k
J K L M
A00 P FIXED 100
A00 R FLOAT 60
A01 P FIXED 101
A01 R FIXED 30
A02 P FLOAT 45
A02 R FLOAT 72
A03 P FIXED 55
A03 R FLOAT 53
8 rows selected.
or is this?
select b.j,t.c as k,decode(t.c,b.k,l,n) as l,decode(t.c,b.k,m,o) as m
from t,b
where t.a=b.j
order by j,k
J K L M
A00 P FIXED 100
A00 R FLOAT 60
A01 P FIXED 101
A01 R FIXED 30
A02 P FLOAT 72
A02 R FLOAT 45
A03 P FLOAT 53
A03 R FIXED 55
8 rows selected.

Best way to write Pl/Sql

Dear all,
Can someone say the best way writing below stored proc:
procedure missing_authorized_services is
v_truncate_sql varchar2(200);
v_sql varchar2(2000);
BEGIN
v_truncate_sql := 'truncate table missing_authorized_services';
     execute immediate v_truncate_sql;
     commit;
v_sql := 'INSERT into missing_authorized_services select distinct trim(service_group_Cd) as service_group_Cd, trim(service_cd) as service_cd from stage_1_mg_service_request
where (service_group_cd, service_cd) not in (
                    select distinct service_group_cd, service_cd from stage_3_servcd_servgrp_dim)';
execute immediate v_sql;
     commit;
END missing_authorized_services;
/* I am doing select from table and then try to Insert into a different table the result set */
Please guide,
Thanks
J

Hi,
The best way to write PL/SQL (or any code) is in very small increments.
Start with a very simple procedure that does something (anything), just enough to test that it's working.
Add lots of ouput statments so you can see what the procedure is doing. Remember to remove them after testing is finished.
For example:
CREATE OR REPLACE procedure missing_authorized_services IS
        v_truncate_sql VARCHAR2 (200);
BEGIN
     v_truncate_sql := 'truncate table missing_authorized_services';
     dbms_output.put_line ( v_truncate_sql
                    || ' = v_truncate_sql inside missing_authorized_services'
END      missing_authorized_services;If you get any errors (for example, ORA-00955, becuase you're trying to give the same name to a procedure that you're already using for a table), then fix the error and try again.
When it worls perfectly, then add another baby step. For example, you might add the one line
EXECUTE IMMEDIATE v_truncate_sql;and test again.
Don't use dynamic SQL (EXECUTE IMMEDIATE) unless you have to.
Is there any reason to use dynamic SQL for the INSERT?

Best way to write an Wrapper class around a POJO

Hi guys,
What is the best way to write an Wrapper around a Hibernate POJO, given the latest 2.2 possibilities? The goal is, of course, to map 'regular' Java Bean properties to JavaFX 2 Properties, so that they can be used in GUI.
Thanks!

what about this:
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
public class PersonPropertyWrapper {
     private StringProperty firstName;
     private StringProperty lastName;
     private Person _person;
     public PersonPropertyWrapper(Person person) {
          super();
          this._person = person;
          firstName = new SimpleStringProperty(_person.getFirstName()) {
               @Override
               protected void invalidated() {
                    _person.setFirstName(getValue());
          lastName = new SimpleStringProperty(_person.getLastName()) {
               @Override
               protected void invalidated() {
                    _person.setLastName(getValue());
     public StringProperty firstNameProperty() {
          return firstName;
     public StringProperty lastNameProperty() {
          return lastName;
     public static class Person {
          private String firstName;
          private String lastName;
          public String getFirstName() {
               return firstName;
          public void setFirstName(String firstName) {
               this.firstName = firstName;
          public String getLastName() {
               return lastName;
          public void setLastName(String lastName) {
               this.lastName = lastName;
     public static void main(String[] args) {
          Person p = new Person();
          p.setFirstName("Jim");
          p.setLastName("Green");
          PersonPropertyWrapper wrapper = new PersonPropertyWrapper(p);
          wrapper.firstNameProperty().setValue("Jerry");
          System.out.println(p.getFirstName());
}Edited by: 906680 on 2012-7-27 上午10:56

What is best way dealing with large tiff file in OSX Lion?

I'm working with large tiff file (engineering drawing), but preview couldnt handle (unresponsive) this situation.
What is best way dealing with large tiff file in OSX Lion? (Viewing only or simple editing)
Thx,
54n9471

Use an iPad and this app http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=400600005&mt=8

What is the best way to include an xml file in JSP?

I have a jsp page that I need to include an xml file. The xml file
          uses an xsl to render the file. What is the best way to include the
          xml file and still maintain the structure of the style sheet?
          Thanks
          Jennifer


          The best way is using the tag lib. If you cannot, but you can use JAXP, you can
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          javax.xml.transform.Transformer.transform(Source xmlSource,
          Result outputTarget)
          throws TransformerException
          You construct the transformer with you xsl, use you xml file or DOM to form xmlSource,
          and use JSPWriter "out" to form outputTarget (StreamResult). But if your JSP page
          generates the xml itself, tag lib is the only way.
          [email protected] (Jennifer) wrote:
          >[email protected] (Jennifer) wrote in message news:<[email protected]>...
          >> I have a jsp page that I need to include an xml file. The xml file
          >> uses an xsl to render the file. What is the best way to include the
          >> xml file and still maintain the structure of the style sheet?
          >>
          >> Thanks
          >>
          >> Jennifer
          >
          >Or is there a way to parse the xml file with the jsp page to display
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          >Thanks
          >
          >Jennifer

What is the best way to write 10 channels of data each sampled at 4kHz to file?

Hi everyone,
I have developed a vi with about 8 AI channels and 2 AO channels... The vi uses a number of parallel while loops to acquire, process, and display continous data.. All data are read at 400 points per loop interation and all synchronously sampled at 4kHz...
My questions is: Which is the best way of writing the data to file? The "Write Measurement To File.vi" or low-level "open/create file" and "close file" functions? From my understanding there are limitations with both approaches, which I have outlines below..
The "Write Measurement To File.vi" is simple to use and closes the file after each interation so if the program crashes not all data would necessary be lost; however, the fact it closes and opens the file after each iteration consumes the processor and takes time... This may cause lags or data to be lost, which I absolutely do not want..
The low-level "open/create file" and "close file" functions involves a bit more coding, but does not require the file to be closed/opened after each iteration; so processor consumption is reduced and associated lag due to continuous open/close operations will not occur.. However, if the program crashes while data is being acquired ALL data in the buffer yet to be written will be lost... This is risky to me...
Does anyone have any comments or suggestions about which way I should go?... At the end of the day, I want to be able to start/stop the write to file process within a running while loop... To do this can the opn/create file and close file functions even be used (as they will need to be inside a while loop)?
I think I am ok with the coding... Just the some help to clarify which direction I should go and the pros and cons for each...
Regards,
Jack
Attachments:
TMS [PXI] FINAL DONE.vi ‏338 KB

One thing you have not mentioned is how you are consuming the data after you save it. Your solution should be compatible with whatever software you are using at both ends.
Your data rate (40kS/s) is relatively slow. You can achieve it using just about any format from ASCII, to raw binary and TDMS, provided you keep your file open and close operations out of the write loop. I would recommend a producer/consumer architecture to decouple the data collection from the data writing. This may not be necessary at the low rates you are using, but it is good practice and would enable you to scale to hardware limited speeds.
TDMS was designed for logging and is a safe format (<fullDisclosure> I am a National Instruments employee </fullDisclosure> ). If you are worried about power failures, you should flush it after every write operation, since TDMS can buffer data and write it in larger chunks to give better performance and smaller file sizes. This will make it slower, but should not be an issue at your write speeds. Make sure you read up on the use of TDMS and how and when it buffers data so you can make sure your implementation does what you would like it to do.
If you have further questions, let us know.
This account is no longer active. Contact ShadesOfGray for current posts and information.

Best way to write specific information to a file

Hi there,
I'm looking to write specific information from my program to 2 separate files.
Before the program runs, it asks the operator for their info (name, password, run ID #, a couple safety checkboxes).
So, I would like the first file to record log-in information (i.e. The operator's name, the date and time they accessed the program, and the Run ID #) all in a spreadsheet.
I would like the second file to record data from the different components of the program ( 2 tank levels, a flow meter, and run ID #) in another spreadsheet.
Any thoughts on the best way to do this? I've looked at using arrays to organize the info/data, and then write to spreadsheet, but I haven't quite figured it out...
Thanks,
Daryn

For the first, you could convert everything to strings, then send an array of strings. For the second, just send an array of numbers.
Cameron
To err is human, but to really foul it up requires a computer.
The optimist believes we are in the best of all possible worlds - the pessimist fears this is true.
Profanity is the one language all programmers know best.
An expert is someone who has made all the possible mistakes.
To learn something about LabVIEW at no extra cost, work the online LabVIEW tutorial(s):
LabVIEW Unit 1 - Getting Started
Learn to Use LabVIEW with MyDAQ

Best way to write objects in an xml and send the file?

hello all
i am making some objects, which i conver to xml using the XStream and then i am saving them to a file, call a function to send the file to a servant (basically i do this by sending bytes and this may be the problem). In the servant i take the data i write them to a file and then i read them again to make them objects...
i have the following code in the client
        XStream xstream = new XStream(new DomDriver());
        xstream.alias("Jobb", WorkflowFramework.Jobb.class);
     String xml = xstream.toXML(translation);
           FileWriter fw = new FileWriter("translation.xml");
           ObjectOutputStream out = xstream.createObjectOutputStream(fw);
           out.writeObject(new Jobb("ougk2", "Walnes",null));
           out.close();
           File file=new File("translation.xml");
           byte buffer[]=new byte[(int)file.length()];
           try {
                BufferedInputStream input=new BufferedInputStream(new FileInputStream("translation.xml"));
                input.read(buffer,0,buffer.length);
                input.close();
           } catch(Exception e) {
                  System.out.println("Error: "+e.getMessage());
                   e.printStackTrace();
           theRemoteObjRef.translationService(theCallbackObjectRef, buffer);i write the file and then i read it so as to have a buffer of bytes (there should be a better ways..)
the last line sends an objectRef (we dont care about that) and the file in bytes to a server (to be specific to a servant of a server)..
in the servant i do the following
public void translationService(TheCallbackInterface objRef, byte data[]){
          try{
                    File file = new File("translation2.xml");
                BufferedOutputStream output = new BufferedOutputStream(new FileOutputStream("translation2.xml"));
              output.write(data, 0, data.length);
              output.flush();
              output.close();
          } catch(Exception e) {
                    System.out.println("Error: " + e.getMessage());
                    e.printStackTrace();
           XStream xstream = new XStream(new DomDriver());
           try { // If an error occurs, go to the "catch" block
                FileReader fr2 = new FileReader("translation2.xml");
                ObjectInputStream in = xstream.createObjectInputStream(fr2);
                Jobb newJob = (Jobb)in.readObject();
               System.out.println(newJob.getObjServerRef());
               System.out.println(newJob.getForTranslation());
               System.out.println(newJob.getTranslated());
                }catch (Exception e) {
                     System.err.println("File input error"+e);
                Jobb testJob=new Jobb("ougka","mpougka","falalala");
                System.out.println(testJob.getObjServerRef());
                   System.out.println(testJob.getForTranslation());
                System.out.println(testJob.getTranslated());
the problem is that in the first group of System.out.println i get the error File input errorcom.thoughtworks.xstream.mapper.CannotResolveClassException: Jobb : Jobb
but the second group of printlns, prints the correct results...
do you know what is the problem? Why can i read the content of the file and get the objects from there?
do you have any suggestions of writing and reading the file in an another way or to send it by NOT using a bytes array?
do you have an alternative way of making the xml file?
many thanks!

Hi,
I would suggest to reconsider building of your document so that it doesn't contain duplicates if you don't need them. And it doesn't have much to do with DB XML then.
Also you could insert your document with duplicates and use XQuery Update facilities to delete undesirable nodes.
Vyacheslav

Best way to write waveforms to file

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