Level gauges are sensing and measuring devices used to monitor the level of a fluid in a tank or other storage container. These instruments are commonly used in industrial process applications to monitor fluid levels in drums, tanks, pressure vessels, and other similar applications.

The gauge comprises numerous pieces, including a head, float, measuring tape, bottom anchored bracket, guide wires, elbows, anchors, coupler, pipe support brackets, and pipework.

Level gauges have various benefits, including tolerating high pressure, temperature, and vibrations in difficult situations. They can be used in conjunction with a switch or alarm in a system and are easily read from a distance. They need minimum maintenance, may be repaired without disrupting the system, and can be tailored for demanding applications.

Level gauges are frequently used when a direct physical measurement of the fluid’s level is either impossible or impractical, such as when the fluid being measured is toxic, or the tank or vessel carrying the liquid is sealed and under pressure.

How do Level Gauges work?

There are multiple varieties of level gauges, and describing them may be done by the underlying technical principle or by the intended use. 

Level devices operate under three different main principles:

  1. The position (height) of the liquid surface
  2. The pressure head
  3. The weight of the material


The following are examples of popular types of level gauges:

  • Reflex level gauges

The functioning concept of reflex glass level gauges is based on light refraction and reflection principles.

Reflex glass level gauges employ glasses with the face configured to feature prismatic grooves with a section angle of 90°. When the chamber is in use, it is filled with liquid in the lower section and gasses or vapors in the top part.

The liquid level is shown by the varied brightness of the glass in the liquid and gas/vapour zones. The reflex level gauges do not require any special lighting. The level may be seen in the daylight.


  • A low-cost and straightforward way of determining the fluid level in a tank or vessel
  • Useful for transparent liquids that are difficult to view directly

Reflex level gauges cannot be utilized when reading the separation level between two liquids, for example.

It is also not the best choice when the process fluid is high-pressure water steam since mica shields must be used to protect the glass from the solvent action of the boiler water.

  • Transparent level gauges

Transparent level gauges are always equipped with two plate transparent glasses that contain the fluid. The fluid level is displayed as a result of the two media’s varying transparency.

Transparent Level Gauges with Mica shields can be used to protect glass surfaces from the corrosive action of the process fluid. Transparent level gauges are especially useful in applications where the glass must be protected from corrosive substances and high temperatures.


  • For corrosive fluids
  • For observation of the interface
  • For observation of the liquid color
  • For steam with an operating pressure > 20 bar
  • For repeated thermal shocks


  • Magnetic level gauges

The Magnetic Level Gauge is utilized for leak detection, environmental safety, and trouble-free use with chemically aggressive, pollutant, dangerous or toxic, combustible or explosive fluid interfaces.

The gauges work on the Archimedes Principle, which asserts that every item immersed in a fluid receives the same buoyant force as the weight of the displaced liquid. Magnetic level gauges are exceptionally robust and can be utilized when glass gauges crack or are destroyed.


  • For chemically aggressive fluid
  • For environment pollutants
  • For inflammable or explosive fluid
  • For working temperatures up to 4000°C
  • For environmental pressure range of 220 bar



There are several level indicators available to meet the requirements of various applications. Fluids are commonly employed in a variety of ways in highly commercial businesses. Determining the amount and level of fluid stored will be extremely difficult without the correct tools.

Also, in cases where the nature of the fluid is hazardous or the location in which the liquid is held such that physically locating the level is impossible, level indicators are critical.

Choose different types of Level Gauges at General Instruments according to your desired application. We are here to deliver customized solutions perfect for your use.