Burkert switches and transmitters for level control

Sensor technology for accurate level control and measurement


Level measurement and control is integral to process control and is used across most industries. Variations in environment (rugged, hygienic, explosive) and application determine which Bürkert level sensor will best suit your application.

Level measurement is divided into point level switching and alarming, or continuous level monitoring/control.

Point Level Switches and Alarms

Point level sensors are used to indicate the level has reached a single discrete liquid height at a preset level. For example, these sensors can be used to automate on/off valves to fill liquid into a tank from a low to a high filling point in a tank. Bürkert point level sensors are types:

  • Tuning fork – available in GP, hygienic, IEC Ex 
  • Float – available in GP, arduous environment, high vibration/shock 

Continuous Level Measurement Transmitters and Control

More sophisticated continuous level sensors (or transmitters) provide real-time level monitoring and reporting. A continuous level sensor measures the fluid level at all points within a measurement range, rather than at a single specific point. Versions are available for contact and non-contact of media.

The continuous level sensor provides an analogue output that directly correlates to the distance from the sensor position, eg. level in the tank. Integrated programming further correlates this to volume.

This analogue signal from the sensor may link directly to a visual indicator or process control loop, forming a level management system.

Continuous level control is a key application for Bürkert as it involves a complete process loop and for continuous level we have supplied transmitters which employ these key principles:

  • Ultrasonic 
  • Radar 
  • Guided microwave 
  • Hydrostatic 

There is a level meter for every type of liquid in any shaped tank at any temperature – and integrated with Bürkert control valves, level sensors easily form a discrete level control loop.

Level Measurement Principles

There are six primary level measuring principles employed by Bürkert, each catering to different applications and conditions.

Ultrasonic Level Sensors
Short ultrasonic pulses are transmitted at 70kHz – these pulses are reflected by the surface of your media. The reflected pulse echo is received by the sensor transducer.

 The echo is proportional to distance travelled and the signal is converted to level height, volume or other as selected. An integrated temperature sensor allows automatic compensation. Built-in echo filters enable use in asymmetric and eccentrically shaped containers, or containers with built-in fixtures that generate a disturbance echo.

  • Non-contact function for solids and liquids 
  • Explosive environment approval 
  • Built for extremely arduous conditions 
  • Ideal for harsh conditions, including mineral processing, washdown areas or water and waste 

Radar level sensors
The integrated sensor antenna emits ultra-short radar pulses to the media being measured. These pulses are reflected by the media surface and received by the antenna as echoes. Radar waves travel at the speed of light, with response time proportional to the distance travelled, and hence to level.

  • Non-contact function for liquids 
  • Explosive environment approval 
  • Tough for chemical, toxic, corrosive media 
  • Hygienic condition version for sanitary processes 

Guided microwave level sensors
High frequency microwave pulses are guided along a steel cable or a rod, transmitted to the media (or product) surface and reflected.

These echoes are received and processed by the sensor’s integrated electronics to determine product level and volume. Available with both rod and chain-type sensor probes, the instruments are preset to the ordered length.

  • Non-contact function for liquids and bulk solids (eg. in silos) 
  • Suitable for large tank measurement up to 32m 
  • Insensitive to dust and steam 
  • Explosive environment approval 
  • Hygienic condition version for sanitary processes (eg. dairy) 

Hydrostatic level sensor

Hydrostatic level refers to a measurement of pressure at the bottom of a tank, and comparison to a reference pressure (generally ambient conditions for an unpressurised tank).

 This uses the principle that fluid creates a specific pressure which is determined by known media density and specific filling level. Therefore a pressure sensor attached to the bottom of a tank measures this pressure – with density known, the tank level may then be calculated.

Hydrostatic level measurement is suitable for virtually all types of fluids and produces very precise measured values, dependent on the accuracy of the pressure transmitter.

Hydrostatic DP (differential pressure) level sensor: where a tank is pressurised, it is necessary to measure the pressure at the base of the tank and the top of the tank. The differential pressure is calculated – this value correlates to level and filled volume.

  • Sensor is in contact with media, high accuracy 
  • Version available for hygienic processes (EHEDG) 
  • Robust for processes with temperature, vibration and pressure shocks 

Float level switch/alarm

A simple float which changes its vertical position in proportion to the level. A magnet in the float generates a constant magnetic field, thus causing a reed contact in this field to switch.

On a float switch, a float with magnet is mechanically connected to a reed contact – the float only moves out of the switch position when the level drops below the float point. Restrictions apply to the use of fluids with a low density (lower than 0.7 g/cm³) and coating fluids.

  • Simple operation and principle 
  • Highly cost effective 

Tuning fork level switch/alarm

The tuning fork is piezoelectrically energised and vibrates at approximately 1200 Hz. When the tuning fork is submerged in product the frequency changes.

 This change is detected and used as a switching command. On-board diagnostics detect interruption of connection with cable, extreme wearing of the fork and the absence of vibration.

  • Simple operation and principle 
  • Hygienic version for sanitary processes 
  • IP67 protection for challenging environments, eg washdown, dust 

Bürkert Universal Level Sensors and Level Control Systems

  • Food and beverage processing 
  • Hygienic processes – dairy, pharma/biotech 
  • Water and waste treatment – civil, industrial 
  • Chemical manufacture – challenging media 
  • Mineral processing – tough environments 
  • General manufacturing – a solution for all conditions

Bürkert fluid control technologies including level transmitters are designed to work together and quickly form simple control loops that integrate into complete process control systems. 

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