Here’s a comparison of the performance and limitations of inductive, capacitive, photelectric and ultrasonic proximity sensors.

It seems like engineering 101, but do you actually remember the specific differences between inductive proximity, inductive displacement, and eddy-current sensors? I asked a few friends and everyone ...

Though it's not their primary role, proximity sensors can be harnessed to detect motion, and sometimes, even measure it. Here are some of the techniques in use today.