![]() ![]() ![]() If a metal target enters this area, the electromagnetic field is reduced and the switch turns on or off. The oscillator creates an electromagnetic field that appears at the active face of the switch. Inductive proximity switches consist of a coil driven by an oscillator. Their high-speed switching and small size make them indispensable in automation applications. Inductive proximity switches are the most common and inexpensive non-contact sensing technology, used to detect the presence of metallic objects without actually touching it. However, since they consist of moving parts, they are prone to wear and damage making physical contact with the sensed object is not always desirable or possible. Actuator styles offer application-specific means of contact – rollers, levers, springs, wands, plungers, etc. The switch operates its set of contacts when its actuator comes into physical contact with the sensed object. The most basic sensor is a limit switch, an electromechanical device used to detect the presence or absence of an object. There are a myriad of object sensing technologies, such as mechanical, inductive, capacitive and ultrasonic devices that detect nearness (proximity) and photoelectric sensing using light beams. Whether you are detecting the presence of an object passing by on a conveyor, the closure of a gate, or the presence of a machine part as it goes through its motions, object detection is a staple of the automation industry. One of the most pervasive functions of a control system is detecting the presence of an object. Let’s look at some of the most common control system functions and some practical ways to implement them. Even when moving from one supplier’s platform to another, the ladder code design can be copied and adjusted for the particular controller, becoming tested “building blocks” of logic to speed up programming and reduce troubleshooting time. ![]() Most every controls designer has implemented at least one of these functions in every system they have commissioned. However, when you start with a blank page to design a new control system, large or small, there are many basic functions this tried-and-true language is still asked to perform, and in fact, perform effortlessly. Ladder logic programming for industrial controllers has evolved significantly over the years, and now supports advanced functionality such as process control, motion control, data manipulation, networking, and data acquisition. ![]()
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