Proximity Switch, Sensor, Square Metal Induction Signal Output Switch

A proximity switch is a sensor that can detect the presence or proximity of an object without physical contact. It is like a switch with a "sixth sense", when an object enters its set detection range, it will act and output an electrical signal. --- 1、 Core Function and Principle ·Core function: Non contact detection, positioning, counting or control. ·Working principle: Different types of proximity switches have different principles, but the commonality is that they do not require mechanical contact with the measured object. 1. Inductive type: detects metal objects. The internal coil generates an electromagnetic field, which changes when a metal object approaches, triggering the switch. 2. Capacitive: detects almost all materials of objects (metal, plastic, liquid, powder, etc.). It detects changes in capacitance caused by object proximity. 3. Magnetic type (Hall effect/reed switch): detects permanent magnets. Commonly used for door and window switches, cylinder piston position detection. 4. Photoelectric type: detects objects by whether the light beam is obstructed or reflected by the object. Sensitive to color and material, with a long detection distance. --- 2、 Main functions and advantages (why use it?) Compared to traditional mechanical limit switches, the prominent advantages of proximity switches are: 1. No contact, no wear and tear: Due to not physically colliding with objects, there is no mechanical wear and tear, and the lifespan is extremely long (up to millions or even billions of operations), with extremely high reliability. 2. High response frequency: It can detect objects in high-speed motion and perform high-speed counting (such as bottle caps passing quickly on a production line). 3. Resistant to harsh environments: It usually has good sealing, can be waterproof, oil resistant, and dustproof, and is suitable for humid, dusty, and corrosive industrial environments. 4. High precision and good repeatability: The position points detected each time are very accurate and consistent, without affecting the object being measured. 5. Flexible application: It can be used to detect small objects, fragile objects, or high-temperature objects (some models). --- 3、 Typical application scenarios in industrial automation This is where proximity switches come into play, with their specific functions reflected in the following aspects: 1. Position detection and localization ·Examples: tool changing position in machine tool magazine, starting/ending position of robot arm, and in place detection of workpieces on conveyor belt. ·Function: Tell the control system that the object has reached the designated position, triggering the next action. 2. Counting and flow control ·Example: Bottle counting on the beverage production line, counting of the number of products passing through the packaging line, and counting of pedestrian/logistics flow at the entrance and exit. ·Function: By accumulating the number of triggers, achieve quantity statistics and traffic monitoring. 3. Travel control and limit ·Example: Detection of piston extension/retraction limit position of cylinders or hydraulic cylinders, leveling positioning of elevators, upper and lower limit positions of elevators. ·Function: To prevent equipment from moving beyond its travel range and provide safety protection. 4. Object presence/absence judgment ·Example: Check whether there is material in the silo, whether a certain part on the assembly line has been installed, and whether the instructions in the packaging box are missing. ·Function: To conduct quality control or process logic judgment. 5. Speed and speed monitoring ·Example: Install metal plates on a rotating shaft or gear, use a proximity switch to detect its passing frequency, and calculate the speed. ·Function: Monitor the operating status of equipment such as motors and conveyors. 6. Safety interlock ·Example: Check if the protective door is closed properly. If the door is not closed properly (proximity switch not triggered), the machine cannot start. ·Function: To ensure personal and equipment safety. --- 4、 Output format After the proximity switch detects an object, it is ultimately output to the controller (such as PLC) in the form of an electrical signal, which is mainly divided into two types: ·NPN type (often referred to as "leakage type"): outputs a low level (0V). It is a common standard in Asia and Europe, often matched with the "common terminal positive (+)" input mode of PLC. ·PNP type (often referred to as "source type"): outputs a high level (such as 24V). It is also a widely used type. ·Normally open (NO)/normally closed (NC): Refers to the initial output state when no object is detected. The normally open type is normally disconnected and conducts when an object is detected; The normally closed type is the opposite. The core function of proximity switches is to act as the "perception organ" of automation systems. It accurately, quickly, and reliably obtains the position, status, quantity, and other information of mechanical components or products through non-contact methods, and converts this information into standard electrical signals, which are transmitted to PLC or controller, thereby achieving precise control and intelligent management of the production process. It is an indispensable basic component in modern industrial automation production lines, CNC equipment, and intelligent logistics systems.