The Magnetic Level Indicator Working Principle: Simple and Effective

The magnetic level indicator working principle is widely used in level instrumentation. The interaction between float magnets inside the chamber and magnetic flags outside the chamber provide virtually maintenance-free, continuous level information. This type of level indicator doesn’t require power, making it ideal for a variety of applications across industries.

The magnetic level indicator working principle is based on the effects that one magnet has on nearby magnets. The mechanics are simple yet very effective, yielding reliable and repeatable level information for continuous monitoring and recording of fluid levels.

What Is the Magnetic Level Indicator Working Principle?

The working principle behind a magnetic level indicator

The working principle behind a magnetic level indicator is that the measuring instrument shares the same fluid — and therefore, the same level — as the vessel. The level indicator is attached to the vessel and connects directly with the fluid to be measured. Within the chamber is a float with a magnet assembly inside. This float rests on the fluid’s surface. As the fluid level rises or falls, so does the float. As the float moves up or down, the magnet assembly rotates a series of bi-color magnetic flags or flaps, changing the visual indicators mounted just outside the chamber from one color to the other. 

Since the magnetic level indicator working principle relies on the interaction between magnets, these level measuring instruments do not need a power source. They are also virtually maintenance-free. An additional advantage: The indicator’s magnetic force can affect optional switches or transmitters mounted outside of the chamber. The colored flags are easy to see, even from a distance, and are paired with a scale for precise readings. As for any level instrumentation, the size and material of the float are chosen according to the media, temperature, pressure, and density of the process media. 

WIKA’s High-Performance Magnetic Level Indicators

WIKA has over 60 years of experience in this field, as our subsidiary KSR-Kueblerobtained one of the first patents for a magnetic level indicator. WIKA manufactures the WMI series, a complete line of high-quality magnetic level indicators that provide years of accurate level information. The float in each MLI is designed for each application. The materials of the float magnet are carefully chosen to minimize the size of the float and the chamber, and to provide the best coupling for the particular pipe wall material and thickness. Bypass chambers can be made of several different types of stainless steel and alloys (Hastelloy^®, Inconel^®, etc.) and other materials (Teflon™, PVC, etc.) to suit media and process temperature.

Model WMI magnetic level indicators are highly adaptable. They work from −320°F to 1,000°F (−195°C to 537°C), from full vacuum to 5,000 psi (344 bar), and for specific gravities as low as 0.35. Indicator flags can be red–white, yellow–black, or fluorescent. The scales can be indicated as imperial units (feet/inches), metric units (mm/cm/m), or percentage, or even customized to your specific requirements. You can also choose from several process connections, connection sizes, vents, and drains. Other useful options include high temperature insulation and cryogenic insulation.

WMI magnetic level indicators fit most industrial and commercial applications in:

• Refinery and chemical industries
• Energy and power plant technology
• Feed water heaters and boilers
• Oil and gas industries
• Offshore exploration and drilling
• Pipeline compressor applications
• Pulp and paper
• Food and beverage
• Gas plants
• Pharmaceutical

A level instrument based on the magnetic level indicator working principle can give you the accuracy and reliability you need. WIKA can help you find the best one for your application.