06-24-2013 11:14 AM
Hi,
I am using the attached VI to log strain gauge data using the 9236 modules in the 9073 case.
The Vi is based on the getting started with Compact RIO logging white paper (http://www.ni.com/white-paper/11198/en), using the Scan interface. I thought I would be able to get 1KHz speed out of it. I have set my scan time to be 10ms on the Real Time CompactRIO properties but when I look at the time stamp created I am more like 0.016-0.020 sec. I have removed the chart and the offset parts of the code to see if it does anything, but it does not make a great difference. If I set it to be 1ms (which is as I understand it the limit of scan interface) I get slower data. If I set it to 1 sec I get 1 sec (so it works but not fast enough)
I am wondering if the time stamp I am using is not accurate enough. I am also concerned that it is not a nice even number of secs between my data points. I want to have as fast a logging as I possibly can.
I did not use the FPGA method as I have had no success getting that to work at all, I will focus on that once I get this up and running well enough to use.
Any help or suggestions would be greatly appreciated.
Steve
06-25-2013 02:52 AM
You shouldn't log the time stamp of the untimed loop. Instead store a time/loop count within your timed loop in addition to a start timestamp for the absolut time calculation.
Hope it helps
Christian