How do automatic-dispensing washing machines know how much detergent you need?

If you don't want to be bothered to weigh out the laundry detergent you need for each load, there are machines that do this ...

What do you look at when setting the automatic detergent dosage? The story of a "2.7x" difference depending on the detergent — Explained by a former home applia…

When did you set the automatic detergent dispenser on your front-loading washing machine? What number did you look at to ...