What Are Proximity Sensors and Their Common Types?

Proximity sensors are a modern technology that allows for nearby objects to be detected without any physical contact being established. In order to detect various objects, proximity sensors will often utilize the emission of an electromagnetic field or electromagnetic radiation so that any changes may be detected when the return signal is received. When discussing the object sensed by the sensor, it is referred to as the proximity sensor’s target. Depending upon the design and implementation of such technology, various applications may benefit from the use of a proximity detector or sensor. In this blog, we will discuss the common types of proximity sensors, allowing you to better understand their uses and functionalities.

Inductive Proximity Sensors

The inductive proximity sensor is a common component that is contactless and may be used to locate metal objects. As such, they are often used within metallic detector equipment and industrial machinery. Inductive proximity sensors rely on the law of induction, utilizing a coil and an oscillator that are driven when a metallic object is near. Such sensors may either be unshielded or shielded, allowing for sensing distances to be controlled as necessary. In order to properly function, such devices will induce an alternating current to the coil, causing an electromagnetic detection field to be generated. As the device approaches a metal object, eddy current will rise and cause a change in coil inductance. Due to the shift in inductance, the sensor’s output switch will be activated in order to allow for a user or system to be notified.

Capacitive Proximity Sensors

Capacitive proximity sensors are another common type, capable of detecting both metallic and non-metallic objects that are in a solid, liquid, powder, or granular form. While similar in construction to the inductive type, their difference is that they have two charging plates for capacitation. For their operations, the capacitive proximity sensor will generate an electrostatic field. As any object moves into the sensing area, both plates will have an increase in their capacitance, causing oscillator amplitude gain. Due to this increase, the output proximity switch will trigger. With their design and functionality, such sensors are commonly used in touch applications, moisture control, non-invasive content detection, and various industrial applications.

Ultrasonic Proximity Sensors

Ultrasonic proximity sensors are a type that detect objects through emissions that are in the high-frequency ultrasonic range. To do this, such sensors utilize the conversion of electrical energy to emit sonic waves. As the sonic waves collide with an object and bounce off, they will return to the sensor so that a reading can be made. Based on the time that it takes for a signal to be sent and returned, the distance of the object can be determined. Ultrasonic proximity sensors are capable of detecting objects that are either solid, liquid, or granular. With their working principle and capabilities, such sensors commonly serve for distance measurement as a proximity detector, wind speed and direction detector, fluid detector, object detector for UAVs, robotics, and automation production processes.

IR Proximity Sensors

IR proximity sensors utilize infrared light to detect objects within their presence, utilizing beam emissions that will collide and bounce off of surfaces. With an IR LED light, infrared light emissions may be sent out to garner a reflection, and a built-in signal processing circuit assists in making a determination. Similar to the ultrasonic proximity sensor, IR proximity sensors are a proximity detector type that can serve for distance measuring. Additionally, such equipment is also used for item counters, security systems, and monitoring and control applications.

Beyond the aforementioned types, there are a number of high-end sensors that may be used for a variety of applications. These include types such as photoelectric proximity sensors, magnetic proximity sensors, LiDAR proximity sensors, and more. As such high-end types are created for very specific and demanding applications, most general users will benefit from the standard set of sensors.

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