Automatic Windscreen Wipers

[ferretneck]

How do they work?

[cupra]

How I understand it, in sort of laymans terms:

Sensor (usually) located behind rear view mirror.
This shines through the windscreen and senses when a drop of rain hits the screen.
Each sensed drop is counted.
The count is then differentiated over a time period (ie: counts/drops per second etc.).
More counts (drops) per second = more rain, therfore wipe faster!

...but the algorithms are probably a bit more complicated than this!

p.s I love them - especially when passing lorries on a wet motorway!