How do I subtract offset voltage from my data acquisition program?

Question

I have a simple program (attached) that reads a voltage input and outputs the results to a file. The voltage has an offset (which changes from test to test), and I am interested in zeroing out this value at the start of acquisition (in the 'interface.vi'). Could someone show me how to do this? Thanks.
Attachments:
finalsystem.zip ‏161 KB

Answer 1

What you need to do is put a Wait millisecond timer in the vi such that it is forced to occur before the data acquisition. You then wire the number of milliseconds that you want to wait into this function. There are a number of ways to force the flow of the data. One method is a state machine architecture. However, this approach requires a rewrite of your code (maybe not a bad idea since the code isn't very large). A second approach uses subvi's with Error in and Error out clusters to regulate data flow. This could be nicely integrated into your vi. I have made a simpler modification to your vi which will make it work by putting some of your inputs to the data acquisition vi into a single frame sequence stru
cture with the Wait function with a five second waiting period.
Once again, this method will work for your vi, but it is not the preferred approach, especially if the vi grows very large.
Hope that helps,
John
Attachments:
interface3.vi ‏94 KB