Hello DiPS.
Thank you for posting to the NI Discussion Forums.
The error that you are getting seems to indicate that incompatible data types are being wired to each other. For example, if you wire a string to an input that expects a number or a boolean value, you will get this error. The output of the power density, as I understand it, is a 1D array of doubles. So, as long as you are comparing it to a compatible data type (an integer, double, some type of number), you should be just fine. In fact, if you were to wire a 1D array of doubles to one input on a 'Greater?' VI and a single numeric to the other input on the 'Greater?' VI, LabVIEW will automatically coerce the single numeric to be a 1D array of numerics of equal length to the first input.
Thus, I think I need more information about the error that you are seeing. After the error saying the source and sink don't match, it should describe the type of the sinc and the type of the source. Can you please post this information? Also, a screenshot of the code that you are trying to execute would be very helpful. Let us know because we would love to help you.
Have a great day!
Brian F
Applications Engineer
National Instruments