Smaller Data Logs

[Arvo]

I am using SignalExpress, full version, 3.5.0 with a cDAQ9174, 9205, and 9217.

The temperature data are 1 sample/s.  The voltage channels are 1000/sec.  I use the DC function on V data and that seems to be 10 samples/s.  I also monitor the AC RMS voltage after a high pass filter.

The test runs for a day or two and I would like the log to keep data every ten seconds or so.

From what I've found, I should be able to use the Statistics function, set it to Mean, set the time for the averaging to ten seconds, then check Restart measurement on each iteration, then log the Statistics data.

However, I cannot find the parameter for the length of the iteration, and the Restart checkbox is not availabe on the DC data.

Thanks for your help!

[John_P1 · Accepted solution]

Hi Arvo,

The DAQmx Acquire steps returns an array of sampled data to be processed--to set the length of the iteration I would change the Number of Samples input to DAQmx Acquire.  For example, if you are acquiring at 1000 Hz, acquiring 10k samples will result in DAQmx Acquire returning 10 seconds of data to be processed.  Just log the DC and RMS values at the end of this processing and the result should be one point every 10 seconds.

Best Regards,

John

[Arvo]

Thanks!  This works.  Now the V channels and the T channels are recording once per second.  We can use this to slow both of them down for longer data collection.

Is there a way for the Data Display to post data faster than the log?

[John_P1]

Hi Arvo,

If you want the Data Display to update at a different rate than the log, I would use the Recording Options to set the acquisition to acquire every 10 seconds:

 

I had to add a software trigger Stop Condition to get this to work but it seems to be what you need.  You can choose which signals to log from the Signal Selection tab.  The display will now update based off of (Number of Samples / Sample Rate) and the log file will be generated independently based off of the system clock.

Best Regards,

John

Message Edited by John P on 12-30-2009 09:14 AM