Hi there,
If you look at the class help for the Thread Safe Variable class (Utility >> Multithreading >> Thread Safe Variable >> Class Help), you'll find a topic on using DefineThreadSafeScalarVar and DeclareThreadSafeScalarVar. According to the class help:
"If you want to use the variable in more than one source file, put the following line in a header file that you include in the source files that use the variable:
DeclareThreadSafeScalarVar (int, MyCounter);"
Do not place the DefineThreadSafeScalarVar in your header file, as this will create multiple definition errors.
Good luck,
Azucena
National Instruments