Level & Pressure Measurement

Level measurement sensors

In continuous level measurement, the level of a medium in a tank or silo is detected and converted into an electronic signal. The level signal is either displayed directly on site or incorporated into a process control or management system. The measured media are liquids, pastes, powders or bulk solids.

Level measurement with radar

In continuous non-contact level measurement with radar, the sensor sends microwave signals towards the medium from above. The surface of the medium reflects the signals back in the direction of the sensor. Using the received microwave signals, the sensor determines the distance to the product surface and calculates the level from it.
Liquids and solids are commonly measured with this measuring technique.

The non-contact level measurement is not influenced by temperature, pressure or product properties.

Level measurement with microwaves

In this type of radar level measurement, microwave pulses are conducted along a cable or rod probe and reflected by the product surface. The measuring probe of the TDR sensor ensures that the signal reaches the medium undisturbed. Liquids, solids and separation layers (interfaces) in liquids are commonly measured with this measuring technique.

The TDR sensors measure reliably even with:

  • Steam generation
  • Pressure and temperature fluctuations
  • Dust and noise
  • Condensation

Ultrasonic level measurement

In non-contact ultrasonic level measurement, the sensor emits ultrasonic pulses in the direction of the medium, which then reflects them back.
The elapsed time from emission to reception of the signals is proportional to the level in the tank. Level sensors based on this measuring principle are ideal for simple standard applications, both for liquids and for solids.

Hydrostatic level measurement

The measuring cell of the pressure transducer detects small changes in hydrostatic pressure, which increases or decreases depending on the filling level. The acting pressure is converted into an electrical signal by the integrated electronics and converted into an output signal.
Different types of measuring cells are used in level measurement based on the hydrostatic principle.

Radiation-based level measurement

In radiometric, i.e. radiation-based, level measurement, the measuring device is mounted outside the tank. A cesium-137 or cobalt-60 isotope sends out focussed gamma rays. On the opposite side of the tank, a sensor picks up the gamma rays that have been attenuated by the medium. The level can be calculated via the intensity of incoming radiation.


Measuring techniques for point level detection

In point level detection, a point level switch detects when a certain predefined level is reached. Such a device is employed when it is not necessary to measure every possible intermediate level, as is the case with continuous level measurement. A switching command starts or stops filling equipment such as conveyors or pumps. Point level switches outputting a binary signal can be integrated into a process control system.
Point level detection systems can be used in liquids, pastes, powders or coarse bulk solids.

Typical applications for point level detection are process tanks, storage tanks, silos and pipelines in the process industry. Point level detection is used for minimum or maximum detection, leak detection or overfill protection.
Every industry places its own specific requirements on the measurement technology it uses. A point level switch perfectly adapted to the measuring point can be supplied by taking the properties of the medium as well as the individual process conditions into account.