Hello,
Your program will be fairly complex, but each of the individual components are commonly used, and there is a lot of example code out there that I would recommend you start with.
The first, most important piece is the data acquisition. You must determine whether you are using a data acquisition card, or whether you have an instrument connected to the computer via GPIB or serial connection. After determining that, you can find some example programs within LabVIEW that acquires data (whether it be DAQ data or GPIB/serial data) and saves it. To access example programs in LabVIEW 6.1 and later, go to Help >> Find Examples. (In 6.0, go to Help >> Search Examples). Then navigate around until you find a suitable acquisition program. Great examples
for DAQ, GPIB and serial can be found in the Hardware Input and Output folder from the Example Finder interface.
The next part of your program is where you take the difference between the data and send it (and the original data) to file. File I/O examples can help you get started with this. I wrote a simple example VI and attached the screenshot to possibly help get you started, too.
If you would like more detail about any portion of your program, let me know what type of acquisition you are performing (DAQ, GPIB, etc), what version of LabVIEW you have, and any other details that you think may help us reach a solution as quickly as possible. I would be happy to help further.
Have a great day!
Liz F
National Instruments
