So im playing in a dark heresy game and im looking at getting an augur array and was looking at the wording for the good version and noticed it says that you reroll all perception based tests is this intended or does it mean only when using the auspex i get to reroll it?

It allows a re-roll on all Perception Tests that could benefit from its presence. This is a passive, not an active effect, meaning that it functions as long as the Augur Array is present and powered. The Tech-Use Test needed for the more detailed scan is still required however.