Introduction to waterproof and oil proof proximity switches for hydrogen stations: Proximity switches are position switches that can be operated by mechanical direct contact with moving parts. When an object approaches the sensing surface of the switch to the operating distance, no mechanical contact or pressure is required to activate the switch, thereby driving DC electrical appliances or providing control commands to computer (PLC) devices. Proximity switch is a type of switch type sensor (i.e. contactless switch) that combines the characteristics of travel switch and micro switch, as well as sensing performance. It has reliable operation, stable performance, frequency response, long application life, strong capability, and features such as waterproofing, shock resistance, and corrosion resistance. The products include inductive, capacitive, Hall, AC, and DC types. Type: Because displacement sensors can be made according to different principles and methods, and different displacement sensors have different effects on objects; Perception; The methods are also different, so there are several common proximity switches as follows: 1. Passive proximity switches. These switches do not require a power source and control the closed state of the switch through magnetic induction. When a magnetic or iron trigger approaches the switch magnetic field, it is controlled to close by the internal magnetic force of the switch. Features: No power required, non-contact, maintenance free, environmentally friendly. 2. Eddy current proximity switches are sometimes also called inductive proximity switches. It utilizes a conductive object to generate eddy currents inside the object when approaching a proximity switch that can generate an electromagnetic field. This eddy current reacts on the proximity switch, causing changes in the internal circuit parameters of the switch, thereby identifying whether a conductive object is moving closer and controlling the on or off of the switch. The object that can be detected by this proximity switch must be a conductive body. 3. The measurement of a capacitive proximity switch is usually based on one electrode that forms the capacitor, while the other electrode is the outer shell of the switch. This casing is usually grounded or connected to the equipment casing during the measurement process. When an object moves towards a proximity switch, regardless of whether it is a conductor or not, its proximity always causes a change in the dielectric constant of the capacitor, resulting in a change in capacitance and a change in the state of the circuit connected to the measuring head. This can control the connection or disconnection of the switch. The objects detected by this proximity switch are not limited to conductors, liquids or powders that can be insulated. 4. Hall proximity switch Hall element is a magnetic sensitive element. A switch made using Hall elements is called a Hall switch. When a magnetic object moves close to a Hall switch, the Hall element on the detection surface of the switch produces a Hall effect, causing a change in the internal circuit state of the switch, thereby identifying the presence of a nearby magnetic object and controlling the on or off of the switch. The detection object of this proximity switch must be a magnetic object. 5. A photoelectric proximity switch is a switch made using the photoelectric effect and is called a photoelectric switch. Install the light-emitting device and photoelectric device in the same detection head in a certain direction. When a reflective surface (the object being detected) approaches, the photoelectric device receives the reflected light and outputs the signal, which can be used to; Perception; There is an object approaching. 6. When the observer or system changes the distance to the wave source in other forms, the frequency of the approaching wave will shift, and this phenomenon is called the Doppler effect. Sonar and radar are made using the principle of this effect. Doppler effect can be used to make ultrasonic proximity switches, microwave proximity switches, etc. When an object approaches, the reflected signal received by the proximity switch will generate a Doppler frequency shift, which can identify whether an object is approaching. Selection: For different materials of detection bodies and detection distances, different types of proximity switches should be selected to achieve better performance in the system. Therefore, the following principles should be followed in selection: 1.1. When the detection body is made of metal materials, frequency oscillation type proximity switches should be selected, which are sensitive to detection of iron nickel and A3 steel. The sensitivity of aluminum, brass, and stainless steel detection bodies is high. 1.2. When the detection body is made of non-metallic materials, such as; Capacitive proximity switches should be used for materials such as wood, paper, plastic, glass, and water. 1.3. When metal and non-metal materials need to be detected and controlled remotely, photoelectric proximity switches or Chaoshengbo proximity switches should be selected. 1.4. When the detection body is metal, if the detection sensitivity is required from time to time, Jiege's magnetic proximity switch or Hall type proximity switch can be selected. Waterproof and oil proof proximity switches for hydrogen stations; nine hundred