Inductive coupler
Inductive couplers are special transformers in which the transformer core can be divided, i.e. both parts can be separated from one another. The primary winding sits on one part of the core and the secondary winding on the other.
Layout and function
The functionality corresponds to the usual transformer principle, but the alternating magnetic field must also bridge the air gap between the core halves. This is only possible with short distances and with additional losses.
As with the transformer, you can transmit electrical energy or messages or data. The inductive coupler is always used when there are reasons to physically separate the primary and secondary windings for a certain period of time.
The rotary joint represents a special form of the inductive coupler. With it there is the additional possibility that one coupler part is, for example, on an axis and rotates while the other part is at rest. Special core shapes are necessary here, such as B. immersing pot cores.
The picture on the right shows a circuit that allows the signal from one pair of lines to be cross-talked to another pair. They can be understood by running a signal on a pair of wires. One of the couplers reduces the voltage and the other reduces the current. The impedance is thus adjusted and there are no reflections. The relative signs of the voltage and current induced in the second pair of wires determine the direction in which the signal travels.
For a 3 dB coupling, i.e. H. An even splitting of the signal can be a different view easier: Two of the line pairs are combined in a three-phase line. A three-phase transformer can then translate the now vector signal to a set of conductors that is rotated by 45 °, which are then separated again.
Application examples
- Underwater couplers are used in the oil / gas production in the sea. Here one coupler part is mounted at the drilling site on the seabed, and the drilling rig lowers the other coupler part on a cable from above. The couplers transmit, for example, energy to trigger valves and data from control units. Advantage: an oil rig can switch between several boreholes very quickly.
- Telephone receiver with inductive coupler: People with hearing aids receive the acoustic voice signals inductively transmitted directly into their hearing aid (special telephones, especially for senior citizens, have this option).
- Readout coupler for measuring devices: Measuring devices such as B. Electricity, gas and water meters can be read by an employee of the utility company using an inductive coupler. Existing systems in the USA, where such meters are often outside the home, allow the consumption data to be read off quickly without access to the home.
- Charging stations for battery-operated small devices, in which the charging energy is transferred without contact, i.e. without a plug contact, from the base station into a winding in the device, e.g. B. Electric toothbrushes .
literature
- Thomas Görne: Sound engineering. 1st edition, Carl Hanser Verlag, Leipzig, 2006, ISBN 3-446-40198-9
- Hans Joachim Geist: Large practical book of communication technology. 1st edition, Elektor-Verlag, Aachen, 2001, ISBN 3-89576-109-5
- Harry Dittrich, Günther Krumm: Elektro-Werkkunde Volume 5 / Professional experience for telecommunications fitters and telecommunications mechanics. 4th edition, Winklers Verlag, Darmstadt, 1971
- Helmut Röder, Heinz Ruckriegel, Heinz Häberle: Electronics 3rd part, communications electronics. 5th edition, Verlag Europa-Lehrmittel, Wuppertal, 1980, ISBN 3-8085-3225-4