Float switch
Float switches are switching devices that are operated by a float moved by a liquid .
purpose
Float switches are used for the automated control of fill levels in liquid containers. The hysteresis between the switch-on and switch-off point is characteristic of every float switch, which results in corresponding level fluctuations.
example
So a float switch z. B. falls below a certain level a valve open to liquid in the container refill or if it exceeds a certain level a pump turn on, in order to lower the level.
Another typical application is submersible pumps , which are usually equipped with an electrical float switch that switches off the drive when a minimum level is reached in order to avoid dry running.
Executions
The most common types are float switches,
- whose float is fitted with a ball in a hermetically sealed housing, which changes its position depending on the inclination as a result of the shift in the center of gravity on a predetermined guideway. An electrical contact is operated via a lever system.
- Open float switch of a dirty water pump
Float switch (on)
Float switch (off)
- whose float is guided and provided with a permanent magnet , whose magnetic field activates a reed contact or a Hall sensor with an electronic trigger circuit.
- whose float operates an electrical switch via a mechanical linkage.
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- whose float acts directly on a valve, e.g. B. the so-called float needle valve in the carburetor of internal combustion engines or the float ball on the float valve in the cistern of the toilet flush .
Level switch
- Level switches are operated by the pressure of a column of liquid via a membrane . Such level switches are often found in washing machines or dishwashers . One variant is the differential pressure membrane switch with two media connections.
- Electronic level regulators evaluate the electrical resistance of a column of liquid.
Echo level measurements
Echo level measurements are also used for level control, but are not part of the float switches. In terms of the design principle, there is an alternative to the vibrating level switch .
See also
literature
- Wolfgang E. Schmidt: Learning situations energy and building technology for electronics technicians and electrical installers. 1st edition, Verlag Handwerk und Technik GmbH, Hamburg, 2005, ISBN 3-582-03671-5
- FANAL circuit practice. 7th edition, Metzenauer & Jung GmbH, Wuppertal
