Cond Retrieve Trigger only logs data around set point?

Question

I need to acquire analog data after a set point level is reached until the signal falls back below that set point. The max level will be realtively high compared to the set point. I only seem to be logging data around a very narrow band relative to the set point. The vi is attahced. Thanks!
Attachments:
Force_Monitor3.vi ‏103 KB

Answer 1

Well, that still didn't include your trigger level VI. No matter. First, upon taking a further look at your loop, you start a buffered continuous analog acquisition, but you don't have anything wired to the "number of scans to read" input of your AI read VI. The default for this input is -1, which means you read the entire buffer. This is not the setting you want when doing a continuous acquisition; you may get overrun errors doing this. You want to read a constant amount of data out of the buffer at a time, and it has to be less than your buffer size.
Second, this is not a limitation of your DAQ board. As long as your DAQ board can do buffered analog input, the triggering you are using is a software trigger, which is NOT a function o
f the DAQ board. The AI Read VI reads the data out of the buffer, and then based on the trigger specifications, determines whether or not this data should be passed out of the VI.
Since your arrays are not particularly large, I think it best to do it a different way. For example, the way you are doing it, the AI Read VI will return part of the buffer when the trigger occurs, but then stop because the next reading from memory that it does may not satisfy trigger conditions (no "edge", rising or falling).
Therefore, I propose that you get EVERY piece of data out of the AI Read VI (no trigger at all), and search through a particular channel's data for your trigger level. The first value that is above the trigger, get the rest of the data from that array. Then search the next arrays that come from AI Read VI until the value goes below the trigger value, and stop the acquisition when this occurs.
I can show you how to do that. It's not that difficult.
Mark