Magnetic Float Sensor FS37A (Vertical)

The Magnetic Float Sensor FS37A (Vertical) is a compact and reliable liquid level detection sensor designed to monitor the level of liquids in tanks, reservoirs, containers, and pipelines. It operates using a magnetic reed switch enclosed within a vertical stem and a floating ring containing a permanent magnet. As the liquid level rises or falls, the float moves along the stem, causing the magnet to activate or deactivate the internal reed switch. This simple yet effective mechanism provides a digital ON/OFF signal that can be used to control pumps, trigger alarms, or monitor liquid levels in various industrial and domestic applications.

The FS37A is a passive sensor, meaning it does not require a dedicated power supply for the switching element itself. It functions as a mechanical switch and can be connected directly to digital input circuits, relays, PLCs, or microcontrollers such as Arduino, Raspberry Pi, ESP32, ESP8266, STM32, PIC, AVR, and other embedded development boards. Depending on the installation, the sensor can operate as either a Normally Open (NO) or Normally Closed (NC) switch by simply reversing the orientation of the float, providing flexibility for different control applications.

The FS37A Magnetic Float Sensor is commonly rated for switching voltages up to 100 V DC (or up to 220 V in some variants), with a maximum switching current of approximately 0.5 A and a switching power of about 10 W. The float is typically made from polypropylene (PP), making it resistant to water and many non-corrosive liquids, while the stem is constructed from durable plastic or stainless steel depending on the model. Since the sensor carries only a limited current, a relay or contactor should be used when controlling high-power electrical loads.

The working principle of the sensor is straightforward. When the liquid level reaches the float, the float rises due to buoyancy and moves the embedded magnet close to the reed switch inside the stem. The magnetic field causes the reed switch contacts to open or close, producing a digital signal that indicates whether the liquid has reached the desired level. As the liquid level decreases, the float moves downward, reversing the switch state. This simple contact-based operation provides fast response, high reliability, and long service life without requiring complex electronics.

The Magnetic Float Sensor FS37A is widely used in automatic water tank controllers, overhead water tanks, underground reservoirs, sump pumps, aquariums, hydroponic systems, water purifiers, coffee machines, industrial liquid level monitoring, chemical processing, irrigation systems, fuel tanks, and home automation projects. It is also commonly used in IoT-based water level monitoring systems where microcontrollers continuously monitor tank levels and automatically control water pumps.

The main advantages of the FS37A Vertical Magnetic Float Sensor include simple construction, reliable liquid level detection, low cost, no external power requirement for switching, compact size, easy installation, low maintenance, corrosion-resistant materials, long operational life, and compatibility with various electronic control systems. However, the sensor is intended for liquid level detection only and should be used with clean or non-corrosive liquids. Care should also be taken not to exceed its rated switching current, and a relay should be used for controlling high-current electrical equipment.

Overall, the Magnetic Float Sensor FS37A (Vertical) is an efficient, durable, and easy-to-use liquid level switch that provides dependable ON/OFF level detection for a wide range of domestic, industrial, automation, and IoT applications. Its simple magnetic reed switch design, flexibility, and compatibility with modern microcontrollers make it an excellent choice for students, hobbyists, engineers, and professionals developing liquid level monitoring and automatic control systems.