Level Measurement

What is a radar level transmitter and how can it be used to do the level measurement?

What is a radar level transmitter and its working principle?

A radar level transmitter can be used to measure the level, it uses the microwave pulse to do the measurement. So it will transmit a microwave pulse and then it calculates the time taken by the pulse to reflect back and that’s how it measures the level. We must consider the frequency for the radar different frequency is used for different applications. Radar level measurement is similar to microwave level measurement because both of them use electromagnetic waves.

The radar transmitter transmits the microwave pulse and the microwave energy will be reflected from the product surface and the sensor in the device would receive this energy. The time from transmitting the signal and receiving the microwave energy is measured then this time will be converted to distance measurement and then to level.

What are the factors that would affect the reliability and accuracy of process-level transmitters?

  • Density
  • Dielectric constant
  • Conductivity
  • Temperature
  • Pressure
  • Vacuum
  • Vapors and condensation
  • Dust

How does a radar level transmitter work?

Mostly a radar transmitter would be mounted on the top of the tank and the transmitter’s antenna would transmit microwaves and this would reach the fluid’s surface that is to be measured. The reflected microwave will be picked up by the antenna and the received signal would be varying in frequency. So the frequency of the received signal will be slightly different from the transmitted signal and the frequency difference will be proportional to the distance to the product surface, and so the level can be accurately calculated.

How to select a radar level transmitter?

  • The radar transmitters have many types of antennas and this could be selected according to the application
  • While measuring vapor and foam we can use low frequency
  • The high frequency is used for other applications rather than vapor and steam
  • If the radar transmitter is mounted in the vessel then we should use isolation valves with it

How to install a radar level transmitter?

These transmitters would be mounted on the top of the vessel without a standpipe or valves. If the radar is installed in a nozzle then we should check the tank drawings before selecting the antenna. The sensors must be perpendicular to the surface, the mounting socket on the top of the vessel must be short.

What is the difference between radar and ultrasonic level transmitter?

The radar transmitter uses radio waves while the ultrasonic level transmitter transmits the sound waves. The radar transmitter has an advantage over the ultrasonic level transmitter which is it doesn’t need a medium to transmit because of the electromagnetic waves.

What are the advantages of non-contact radar level measurement?

  • It can be used for solid and liquid level measurements
  • It has high accuracy
  • It is a non-contact type
  • Less maintenance is needed because of the non-contact transmitter
  • It can handle long measurement

The radar is not affected by certain process conditions like

  • Temperature
  • Pressure and vacuum
  • Conductivity and dielectric constant
  • Specific gravity
  • It is not affected by dust, steam, or movement of air

How to choose the frequency for radar level transmitters?

  • It must be selected according to the mounting
  • The dimension of the vessel must be considered
  • We must consider the presence of the foam,
  • The internal structure of the vessel must be considered
  • Dielectric constant

The low frequency is suitable for foam, steam, dust, mist, dish bottom vessels, heavy agitation, and severe build-up. High frequency is suitable for small vessels, it doesn’t need a larger antenna and it doesn’t have the problem of false echoes.

What are the disadvantages of radar level transmitter?

  • It is really expensive
  • These sensors would respond to build upon the sensor face

What are the applications of radar level transmitters?

  • Guided wave radars are used to measure the level of fluids and dry media
  • Non-contact type radars can be used to detect the dry fluids and also it can detect surfaces that detect energy
  • Radar transmitter can measure level through plastic tanks
  • By using this we can check the contents of boxes
  • It can also be used to detect obstructions


post-graduate in Electronics & communication.

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