How to trigger data recording to a text file for multiple channels for a certain voltage threshold?

Question

I am working with 6 channels, from each of which I am obtaining voltage values ranging from 0.6-6 V.  I am using the DAQ Assistant to acquire and write the data to a text file.  However, I only want the data to be written to the text file when the difference in voltage (DeltaV) from one data point to another is greater than or equal to 0.04 V.  I am acquiring the data at a sampling rate of 64 Hz.  Any ideas on how to accomplish this?  I have attached my current VI. 
Attachments:
Data Triggering.vi ‏116 KB

Answer 1

Faizah wrote:
I am obtaining voltage values ranging from 0.6-6 V.  
I only want the data to be written to the text file when the difference in voltage (DeltaV) from one data point to another is greater than or equal to 0.04 V.  
Your code does not do what you describe above..
I just want to make sure I understand your request...
Let's say you have the following signal:
0.00
0.01
0.00
0.03
0.02
0.01
0.03
0.04
0.07
0.05
0.08
0.03  < delta greater than 0.04, so start recording
0.11
0.21
0.45
0.93
2.87
5.85
5.86 < delta less than 0.04, so stop recording
5.87
5.89
6.00  < delta greater than 0.04, so start recording
5.85
5.86  < delta less than 0.04, so stop recording
etc..
Is the above what you are describing?  
Right now, your code does this:
0.00
0.01
0.00
0.03
0.02
0.01
0.03
0.04
0.07
0.05
0.08
0.03 
0.11
0.21
0.45
0.93
2.87 < threshold greater than 1 so reset timer
5.85 < threshold greater than 1 so reset timer
5.86 < threshold greater than 1 so reset timer
5.87 < threshold greater than 1 so reset timer
5.89 < threshold greater than 1 so reset timer
6.00  < threshold greater than 1 so reset timer
5.85 < threshold greater than 1 so reset timer
5.86  < threshold greater than 1 so reset timer
4.35 < threshold greater than 1 so reset timer
2.21 < threshold greater than 1 so reset timer
1.09 < threshold greater than 1 so reset timer
0.98 
However, you did not provide a set start time  to the Elapse Time (I never use Express VI's so I'm not sure what will happen..) However, something does not appear correct with the logic.  I'd have to check.