Skulk Sensors do not detect several things.

Several events do not trigger skulk sensors, including (but most likely not limited to):
-pistons, dispensers, and droppers firing
-armor equipping
-food, potions being consumed.
-tnt exploding
-ringing bells
-placing sea pickles
-placing powder snow from a bucket (breaking it activates the sensor as normal)

These were just the things i immediately noticed. I will update with new testing.