A proximity sensor is a sensor that is able to detect the presence of nearby objects without physical contact. A proximity sensor often emits an electromagnetic or electrostatic field, or a beam of electromagnetic radiation (e.g. infrared) and looks for changes in the field or return signal. The object being sensed is often referred to as the proximity sensor's target. Different proximity sensor targets require different sensors. For example, a capacitive or photoelectric sensor might be suitable for a plastic target and an inductive proximity sensor may be suitable for a metal target.
Usually, a proximity sensor includes a transmitter and a receiver. When a target is placed in range of the proximity sensor, the target reflects electromagnetic energy (e.g. light) emitted from the transmitter to the receiver. The receiver then sends a signal that indicates that the target is in range.
Proximity sensors may be used for many purposes. For example, a proximity sensor is often used with a water faucet to automatically turn on the water when a person's hands are near the faucet. In another example, proximity sensors may be used to monitor machine vibration while measuring the variation in distance between a shaft and its support bearing. The use of proximity sensors to monitor vibration is common in large steam turbines, compressor and motors.
As automation equipment becomes smaller, the packaging size of proximity sensors need to be become smaller as well. In addition, the cost of manufacturing a proximity sensor should be lowered in order to be competitive. One method for reducing the cost of manufacturing proximity sensors is to reduce the number of steps needed to manufacture proximity sensors.