If someone says proximity sensor, what is the first thing that comes to mind? My guess is inductive and justly so because they are the most used sensor in automation today. There are other sensing technologies that use the term proximity in describing the sensing mode. These include diffuse or proximity photo electric sensors that use the reflectivity of the object to change states and proximity mode of ultrasonic sensors that use high frequency sound waves to detect objects. All of these sensors detect objects that are in close proximity of the sensor without making physical contact.
One of the most overlooked or forgotten proximity sensors on the market today is the capacitive sensor. Why? Perhaps it is because they have a bad reputation from when they were released years ago, as they were more susceptible to noise than most sensors. I recently heard someone say that they don’t discuss capacitive sensors with their customers because they had a bad experience almost 10 years ago. With the advancements of technology this is no longer the case.