New to signal express and I have a few questions

[JaRay200]

For an upcoming test we plan to use an old SCXI-1001 chassis, an SCXI-1600 Daq, and 7 SCXI-1520's along with the SCXI-1314's to measure 50+ channels of strain gages.  I'm planning to use Signal Express to set the project up since the requirements for the data will be primarily logging.  I have a few questions about how signal express handles logging along with how it handles offset nulling.

The test will consist of measuring the 50+ channels at 500 Hz for around the clock measurements.  The specimen will be under going cyclic loading for failure analysis.  Once thing I have noticed about Signal Express is that the data seems to be logged to an individual file for each measurement type.  With most of these being strain that means that each channel will be saved to one data file.  I ran a test with 40 channels to see how large the file would get, and it reached 400 MB within an hour.  Is there a way to limit the individual files to certain size and create a new one once the size is reached?  There will be routine inspections during the test where the systems is stopped, so data could be dumped to an external harddrive during this period, but I would like to limit the file size for processing purposes later.

My other concern is how offset nulling is handled.  What I would like to do is obtain a single offset value for each channel in the beginning of the failure testing before load is applied and have this value be applied for the entirety of the test.  This does not seem to be a problem with signal express from what I can tell using calibration feature, but what happens if I lose power during this test.  If I reload the project will the calibration values be persistent?  

I am sure I will run into other issues as I explore the software, but these are the two biggest concerns I have right now. 

[NIYiran]

Hi Jason,

Under Recording Options for your DAQmx Acquire step, you should have the option to start and stop recording based on Date/Time. Although it's not as dynamic as it would be in LabVIEW, you can if nothing else set your recording length to limit approximately how large the files will be through there. As for the offset nulling, I believe that the calibration values are stored from run-to-run. However, the easiest way to verify that would be simply be to test aborting execution (e.g. by ending the SignalExpress task in Windows or otherwise) to see if the calibrations stay. 

[OKors]

How are you logging your data? 
Are you using the actual "Record" function where you set up parameters in the Recording Options tab or do you use the Save to ASCII step?

If all you're after is a simple ascii file with all your channels in one file I'd use that step rather than the often combersome Record feature. Also I like to pass my signals through the Amplitude and Levels step (especially with strain channels). This will take the raw waveform data and smooth it out, thus creating much cleaner, and smaller data files. You will loose your time column because of the averaging that SE does while smoothing the signal out but its easy to calculate;  your new sample rate is now the Rate in HZ divided by Samples to read. So if your at 1kHz and 100 samples to read you're sampling at 10S/s. 

Your calibration/zero offset properties will not get lost during an outage. Just remember to save the SEproj file. 
Furthermore you can add a Zero Offset step which allows more offsetting options. 

[JaRay200]

It sounds like I will be able to accomplish what I need to with Signal Express.  I will simply be logging data, but over a long period of time.  I plan to work with it a bit more today or tomorrow to setup a test to run for a while to make sure there are no lockups or anything.