[giraffe_lady]

Do they? Mine noticeably takes much longer to run on very dirty kitchen towels compared to clothes, even on the same setting and even though the clothing load is heavier. I had been assuming there's something to detect how soiled the water is.

[toast0]

Random fact of the day: (some?) Dishwashers detect soiled water by using a resetable fuse on the water pump and counting how many times the fuse trips; dirty water makes the pump work harder and trip the fuse.

I don't think that would work for clothes washers though, because there isn't the same kind of pumping water for recirculation. Somewhat related, my washing machine (upright, high efficiency) measures the load by spinning it with a calibrated input impulse and measuring the rotation of the basket, less rotation means more clothes means more water. It's helpful to load the clothes around the edge to get the right amount of water. But that doesn't illuminate how cycle duration is determined.

[xnzakg]

Not all of them do, I've taken apart a Siemens dishwasher (pump was clogged) and it has a turbidity sensor to check if the water is clean or not.