A magnetic liquid level switch consists of two main components: a magnet embedded inside a float, and a reed switch placed in an enclosure. The single unit or multiple reed switch units are housed tightly in a stainless steel or an engineering plastic stem and a permanent magnet is sealed inside a float whose rise and fall causes the actuation of the reed switch.
The float rides on the process liquid surface, precisely tracking liquid surface motion. Rising liquid level lifts the float, sliding the attraction sleeve up inside the enclosing tube and into the magnetic field to actuate the electrical or pneumatic switch. This signals the presence of liquid.
Subsequently, falling liquid level lowers the float, drawing the attraction sleeve out of the magnetic field to deactivate the electrical or pneumatic switch. This signals the absence of liquid. Magnetic float level switches are generally able to handle high-temperature applications, and sometimes prove useful for close interface detection.
By using a permanent magnetic float level switch and reed contact the switching operation is non-contact, free from wear and needs no power supply. All functioning of the magnetic float switch is fully independent of vibrations, bubble formations, foaming, conductivity, and harmful vapors.
A vibration type level switch working principle is based upon detecting the change in harmonic vibration frequency of the sensing element as a result of the presence of the target media. It uses a tuning fork shaped sensing element with two tines inserted into the bin or tank where the target media will be present. The tuning fork sensing element is placed into vibration at its natural resonant frequency by establishing motion in the sensing element.
When the fork sensing element vibrates free in air the measuring system sees this as one state (material not present). When the target material or fluid becomes present, the frequency of the vibration is changed, thereby detecting the material or fluid presence.