Valve four kinds of limit switch technology principle

Mechanical limit switch

A mechanical limit switch is an electromechanical device that detects the position of a target through direct physical contact with the target. They do not require power to operate and can handle large current loads. Because mechanical switches use dry contacts, they are not polarity or voltage sensitive and are protected from many electrical defects, such as electrical noise, RF interference, leakage current, and voltage drop. These switches often include multiple moving parts that may require maintenance (lever arms, buttons, body, base, head, contacts, terminals, etc.). Because Votto mechanical limit switches operate in physical contact with the target, their repeatability can be poor. Physical contact causes wear on the lever arm and even the target itself. In addition, there are unsealed openings with poor protection against moisture, dust and corrosion. As a result of this problem, sealed contacts and hazardous area certification typically increase in cost significantly.

Spring limit switch

The spring limit switch is an electromechanical device that detects the position of the magnetic target by attracting the magnetic field of the target. Inside the switch are two small metal pins and the gas is sealed in a glass tube. This is called a "reed element". The reed element is magnetically sensitive and activates when a magnetic target passes close by. Spring limit switches have almost all the advantages of mechanical switches and avoid wear and tear problems by operating without relying on physical contact from the target. With a spring limit switch, normal black metal targets cannot be used; You need a magnetic target. The reed element is fragile, the glass tube is destructible, and the small metal prongs are subject to fatigue from bending, causing the reed switch to become unreliable. Due to the low contact pressure, the application of high vibration can lead to contact chatter and false signals from the reed.

Inductive proximity sensor

Inductive proximity sensors are solid-state electronic devices that detect the position of metal targets by interference of their energy fields. No physical contact is required, and there are no moving parts to block, wear or break, resulting in less maintenance. The lack of moving parts also means it is not affected by dust or dirt. There are a large number of shapes and sizes to choose from, so inductive proximity sensors are highly customizable for a variety of applications. Inductive proximity sensors require external power (electricity) to work and cannot handle large current loads. In addition, they may be susceptible to electrical noise, RF interference, leakage current, and voltage drop. Inductive proximity sensors are sometimes adversely affected by extreme temperature fluctuations and moisture intrusion.

Limit switch

The limit switch uses a unique hybrid technology to detect the position of iron-containing targets through electromagnetic fields. Rugged, long-life, rodless limit switches are extremely reliable in harsh environments and difficult applications. No physical contact or external power supply is required, so no clogging, bending, breaking or grinding and high current loads are possible. Like mechanical switches, they are not polarity or voltage sensitive and are not affected by electrical noise, RF interference, leakage current and voltage drop. Limit switches are not affected by dust, dirt, moisture, physical contact, or most corrosive or chemicals. Most models are inherently safe and have a wide operating temperature range. With its sealed contacts and all-metal housing, rodless limit switches are ideal for explosion-proof and waterproof applications.

Position sensors play an important role in industrial automation. There are several different position sensor technologies available, each with a unique set of performance characteristics. Care should be taken to select the right type of sensor for the application to achieve the desired reliability and performance.