Level Measurement

What is level measurement and what are the types of level measurement?

The level measurement is a measurement of fluid level, the measure of height is called a level, like the fluid level in a tank. The measurement of level is very important in a process, so by doing level measurement we can make sure the process is safe. The level measurement is categorized into the top-down and bottom-up level, the top-down measurement is not susceptible to leakage or it can be considered as less leakage process. The top-down measurement could make a contact with the fluid or sometimes it won’t, while the bottom-up type makes contact with the process fluid. The level measurement is not only done for fluids it is also used to measure the level of gases and solids.

The level measuring instruments are suitable to measure the level of gas or fluid and it could be done directly or indirectly which would be done according to the application. A level measuring instrument would act as an indicator that shows the level of the liquid and this information would be carried in the form of AC signals and this is done for the control purpose. The level switches would monitor if the liquid is at a high level or low level according to the set point.

What are the different types of level measurement?

What is a datum line?

A datum line can be considered as the zero points in the level measurement, it is the point in which the measurement is referenced.

What is direct and indirect level measurement?

The direct level measurement is an easy process, this measurement is based on physical principles such as fluid motions, floats, and thermal properties there are many types of level measurement under this category and they are slight gas, float operated, dipstick, dip rods, and lead lines. So basically the direct level measurement is by defining the position of the interface, and the density of the measured material is not a constraint.

The indirect level measurement is done by measuring other quantities like volume. So this method measures level by determining some other parameters such as pressure, weight, or temperature. So it cannot be used to do the measurement of different materials if we need to do that then we need to use a corrosive factor or the recalibration of the instrument must be done.

How to select a level instrument for our applications?

There are different types of level instrument and all of them works on a different principle. So we need to select the level measuring instrument according to the process parameters such as pressure, temperature, medium, etc. We must also consider certain factors to select a level measuring instrument for our applications and they are

  • We must select it according to the tank, like if the tank is open or closed
  • Type of measurement is it direct or indirect
  • The material that is to be measured must be considered as if it is liquid, or solid, etc.
  • We must also consider if it is a continuous measurement or point measurement
  • We must also consider how the measuring instrument is placed in the tank, Like is it possible to insert the level sensor into the tank or external. Contact or non-contact

What are the principles of level measurement?

  • Level measurement can be done based on pressure
  • Level measurement can be done by transit time and is divided into two types they are ultrasonic based level measurement and radar-based level measurement
  • Level measurement is also done based on attenuation and radiation
  • Electrical measurement according to the conductivity
  • Capacitance based measurement

So all these are the principles for different types of level measurement

What is a contact and non-contact level measurement?

In a contact measurement, a part of the measuring instrument would be in contact with the medium that it is measuring, floats and dipsticks do this type of measurement. In the non-contact type, the measuring instrument won’t be in contact with the medium that it measures.

What is continuous, single point, and multipoint measurement?

Single point measurement

In this type of level measurement, it shows if the measured medium is high or low according to a specified level. So it basically indicates if the level is high or low level. This type is used to point out the overflow.

Multipoint measurement

In this type, the level is indicated in two or more points in a tank, so these two single points would operate if the level is high or low. If we use several single-point devices in a vessel then it can do almost a continuous level measurement.

Continuous level measurement

In this type of system, the instrument would check the product height according to the range of points within the tank. This type of measurement method is used when accurate control is needed, and it can keep the level of the product at a certain point.

What are the applications of level measurements?

  • Food & beverage
  • Marine & irrigation equipment
  • Mining
  • Water & wastewater

The continuous level and point level measurements are used for applications such as gases, liquids, solids, powders, slurries, etc.

Other topics related to level measurement


post-graduate in Electronics & communication.

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