How is fluid level measurement carried out?

How is fluid level measurement carried out?

The measurement of liquid levels in tanks and certain process equipment is carried out for various reasons, including controlling the liquid level and preventing overflow. When selecting the appropriate device for level measurement, the following factors should be considered:

• Range of liquid level height changes
• Fluid properties such as specific gravity
• Cleanliness or contamination of the fluid
• Amount of vapor or solid particles
• Fluid corrosiveness
• Fluid's tendency to wet the walls of the container or measuring device
• Process temperature and pressure
• Chemical composition
• Environmental regulations
• Presence of vibration
• Humidity
• …etc.

For example, devices that can be selected for measuring the level of clean and non-viscous liquids are more numerous than those that can be selected for slurry and viscous solutions. Generally, the measurement of liquid and solid levels is divided into two categories: Continuous measurement and Point measurement. The goal of point measurement is to determine whether the substance's height in the tank reaches a specified value or not, which is commonly referred to as switching. In contrast, continuous measurement involves the constant monitoring of the substance's height in the tank.

Measurement methods for liquid level height are also categorized based on whether they are in contact with the substance or not. Height measuring devices with contact methods are available in various types, depending on which of the different properties of the fluids they utilize.

For example, devices that use various types of Floaters rely on the buoyancy property, Displacer-type devices operate based on Archimedes' principle, conductivity meters measure fluid conductivity, vibrating forks detect changes in the resonance frequency of fluid-immersed diapasons, and bubble generators or other devices that work with pressure gauges perform liquid level measurement using hydrostatic pressure measurement of the fluid. It is worth mentioning that non-contact methods often operate based on the material's tendency to absorb or reflect radiation. Ultrasonic and radar devices are examples of such methods. A more detailed analysis of the operating principles of each of these devices will follow.