Guidance to integrate 2 VI's

[GoKu25]

Background: I have an event based state machine  (two state machines ) which concurrently reads data from 2 sensors and writes to a text file. The sensors are IMU 500 and an INTRANAV indoor  navigation position sensor. 

I have also developed 2 separate VI's to read data from each sensor and it works fine(just to check if it is working)

Problem: integration of these 2 sensors in a single VI causes error with serial communication using VISA while read and write

I have verified the COM port with NI Max and device manager. 

I'm attaching the screen shots with error and the actual VI

Cheers

[RavensFan]

Did you look up the error code -1073807346 that you get?

It says the session is invalid.  Looking at the your code, I see a number of tunnels including the upper and lower while loops and the VISA reference tunnel set to Use Default if Unwired (generally the wrong setting to use), and that you must have some cases unwired because the tunnel is hollowed out.  So you are probably executing some cases were the VISA reference is not wired through, it is being reset to the default value of zero, and the next iteration your VISA functions fail on that.

The file reference wire at the very bottom almost off screen on your image as the same problem.