Place marker during recording and place back markers

[Rut]

Hi,

I will be recording 5 channels of signals at rate of 200 samples/second for 1 hour or so. Meanwhile, I need to put markers for different user interventions. I would like to save in text file for other applications such as MS Excel. What would be a good format for the data file? One way would be keep adding NaN in an extra column and a message when the user enter a message and press a button. But it takes some space for the extra column and don't konw if other applications can read this column correctly. At the same time when the intervention occurs, need to draw a marker on the screen, and when VI is stopped, these markers need to be back-trackable when scrolling back.

Also, the data file may need a header that keeps track of all interventions in addition to the extra column. At the end, the header needs to join the data record to form the final data file. When playback, theses interventions show markers again on the screen. Also, the data file may need to be appendable.

Any suggestions and/or examples are appreciated. Thanks,

Rut

[RavensFan]

So you would be talkinga bout 1000 pieces of data per second, x 60 sec/min, x 60/min per hour.  So 3.6 million pieces of data per hour.  Lets say 8 bytes per piece of data (depends on how you want to format the numeric value to a string).  So about 28.8 MB of data for one hour.  That isn't too large.  I would use a text based file format such as comma or tab delimited with CRLF at the end.  You could have 6th column that would either be blank or have the text note.  Excel should be able to open either of these just fine.  It would be a good idea to write the data using a producer/consumer architecture.  Accumulate the data to memory in chunks, and periodically write out the chunks to file.

I don't understand what you mean by drawing a marker on screen.  Do you mean have some X show up on a waveform graph?  If so you could create a 6th series of data with Nan interlaced with a numeric value such as 1 (no line and an X or other highly visible  data point) or someother value that shows up well on the graph considering the scale of the other values.  There won't be any easy way to associate an X with a text comment  other than displaying the text in a string indicator and picking it out of the array depending on which portion of the data is shown on the graph at that time.