(only one component per ship effective)

Well, don't they all work?
It's just because they do the same thing you're not likely to notice a difference are you
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I think I just had an evilgasm.....
The (now official?) Space Empires 4 Mod Launcher V2.26

Sensors sound like an item where either your ship has it or it does not have it, the only advantage to having more than one is that the enemy would have to destroy all your sensors to deprive you of the advantage that you get from your sensors.

Which brings up a good design point: Is it possible to mod sensors so that the first one gives a significant range, and then additional ones contribute a small amount of further range?

If you make them different component types...
Could set requirements on the second/third ones (with longer ranges) that they require you to have one unit of the smaller ones first.
So, for example, 3 sensor components - short range sensors, medium range, and long range - all requiring the immediately-shorter-range version to allow placement.
______________________________________________________
I think I just had an evilgasm.....
The (now official?) Space Empires 4 Mod Launcher V2.26