If that one guy is managing to scan you at 200 meters, good for him considering the only scanner that does 200m is the Prototype Flux Active Scanner meaning theyGÇÖve put a lot of SP into it.

As for Profile Dampeners they are a wise choice to skill into if you are worried about being scanned all the time; as they reduce your dropsuit scan profile making you undetectable to most scanners. Each suit has their set scan profile, which is tied to GÇ£Dessa BellsGÇ¥ or dB:
Light Dropsuits - 45 dB
Medium Dropsuits - 50 dB
Heavy Dropsuits - 65 dB

Each level in Active Scanners have their own level of scan precision; meaning they can only scan certain suits within that dB range:
Basic - 46 dB
Advanced - 36 dB
Prototype - 28 dB
Focused Prototype - 15 dB
As you can see the basic scanner won't be able to scan a scout suit as itGÇÖs dB profile range isn't within the scanners dB range: A 46dB scanner cannot acquire something that has a 45 dB scan profile.

If you are running in a medium suit and looking not be be scanned, this means your going to need to gain a 29% reduction to your profile. One way to do this is acquiring level 5 in Profile Dampening and fitting a Complex Profile Dampener, this mean you now be unscannable to any form of advanced scanners. However, if they are indeed using a prototype scanner youGÇÖll be sacrificing too much tank to be unscannable, if they are using a Focused Prototype you're pretty much screwed!

Anyway I hope all that helped to understand Active Scanners.