Difference between revisions of "Lexicon Impedance"

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Auch Scheinwiderstand genannt. Es ist das Verhältnis zwischen [[Lexikon Spannung|Spannung]] über ein Bauelement und dem [[Lexikon Strom|Strom]] durch das Bauelement, ausgedrückt in der Einheit [[Lexikon Ohm|Ohm]]. Die Impedanz eines Bauelements oder einer gesamten Schaltung ist in der Regel frequenzabhängig, weshalb die Angabe der [[Lexikon Frequenz|Frequenz]] meist zusätzlich erforderlich ist. Bei der Frequenz 0 Hz (Gleichstrom) sind Scheinwiderstand und [[Lexikon Widerstand|(Wirk-)Widerstand]] identisch. Bei [[Lexikon Wechselstrom|Wechselstrom]] (Frequenz > 0 Hz) kommen die Effekte reaktiver (Energie speichernder) Bauelemente wie z.B. [[Lexikon Kondensator|Kondensatoren]] und [[Lexikon Spule|Spulen]] dazu.
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Also called impedance. It is the ratio between [[Encyclopedia Voltage|Voltage]] across a component and the [[Encyclopedia Current|Current]] through the component, expressed in the unit [[Encyclopedia Ohm|Ohm]]. The impedance of a component or an entire circuit is usually frequency-dependent, which is why the specification of the [[Encyclopedia Frequency|Frequency]] is usually additionally required. At frequency 0 Hz (direct current), impedance and [[Encyclopedia Resistance|(Active) Resistance]] are identical. At [[lexicon alternating current|AC]] (frequency > 0 Hz), the effects of reactive (energy-storing) components such as [[Encyclopedia capacitor|capacitors]] and [[Encyclopedia coil|coils]] are added.
  
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Weil es immer wieder verwechselt wird:
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Because it is always confused:
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:Der Widerstand (auch Wirkwiderstand genannt) ist ein Gleichstrom-Effekt
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:Resistance (also called effective resistance) is a DC effect.
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:Die Impedanz (auch Scheinwiderstand genannt) ist ein Wechselstrom-Effekt
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:The impedance (also called impedance) is an alternating current effect
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:Der Widerstand ist damit ein Spezialfall der Impedanz bei der Frequenz 0 Hz.
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:Resistance is thus a special case of impedance at frequency 0 Hz.
  
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Beispiel: Ein handelsüblicher [[Lexikon Lautsprecher|Lautsprecher]] der Nennimpedanz 8 Ohm besteht intern aus mehreren Bauteilen, wie Chassis und (in der [[Lexikon Weiche|Weiche]]) Spulen, Kondensatoren und Widerständen. Diese ergeben einen Wirkwiderstand, der bei Gleichstrom mit dem Ohmmeter gemessen werden kann. Die Angabe der Nennimpedanz sagt dabei nicht, daß dieser Wirkwiderstand 8 Ohm beträgt. Sie besagt daß die Impedanz über den ganzen Audiofrequenzbereich nicht mehr als 20% unter die Nennimpedanz fallen darf. Sie darf aber beliebig viel höher sein. Um das zu überprüfen, mißt man die Impedanz bei allen Frequenzen von 0Hz bis über 20kHz, und erstellt ein Diagramm, in dem man die Impedanz über die Frequenz aufträgt. Die Kurve darf dabei nirgends unter 8 Ohm - 20% fallen.
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Example: a commercially available [[Encyclopedia Loudspeaker|speaker]] of nominal impedance 8 ohms consists internally of several components, such as chassis and (in the [[Encyclopedia Crossover|crossover]]) coils, capacitors and resistors. These result in an effective impedance, which can be measured with an ohmmeter in the case of direct current. The indication of the nominal impedance does not say that this resistance is 8 Ohm. It means that the impedance over the whole audio frequency range may not fall more than 20% below the nominal impedance. However, it may be as much higher as desired. To check this, measure the impedance at all frequencies from 0Hz to over 20kHz, and plot a graph of impedance versus frequency. The curve must not fall below 8 Ohm - 20% at any point.
  
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Daraus folgt: Die Impedanz kann man nicht mit dem Ohmmeter messen, denn das mißt mit Gleichstrom. Ein Impedanz-Meßgerät mißt mit Wechselstrom wählbarer Frequenz, und ist damit ein komplizierteres und teureres Gerät.
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It follows: You can't measure impedance with an ohmmeter, because that measures with direct current. An impedance meter measures with alternating current of selectable frequency, and is therefore a more complicated and more expensive device.
  
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Siehe auch: [http://de.wikipedia.org/wiki/Impedanz Impedanz in Wikipedia]
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See also: [http://de.wikipedia.org/wiki/Impedanz Impedance in Wikipedia]
  
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[[Kategorie:Lexikon]]
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[[Category:Encyclopedia]]

Latest revision as of 01:55, 20 September 2015

Also called impedance. It is the ratio between Voltage across a component and the Current through the component, expressed in the unit Ohm. The impedance of a component or an entire circuit is usually frequency-dependent, which is why the specification of the Frequency is usually additionally required. At frequency 0 Hz (direct current), impedance and (Active) Resistance are identical. At AC (frequency > 0 Hz), the effects of reactive (energy-storing) components such as capacitors and coils are added.

Because it is always confused:

Resistance (also called effective resistance) is a DC effect.
The impedance (also called impedance) is an alternating current effect
Resistance is thus a special case of impedance at frequency 0 Hz.

Example: a commercially available speaker of nominal impedance 8 ohms consists internally of several components, such as chassis and (in the crossover) coils, capacitors and resistors. These result in an effective impedance, which can be measured with an ohmmeter in the case of direct current. The indication of the nominal impedance does not say that this resistance is 8 Ohm. It means that the impedance over the whole audio frequency range may not fall more than 20% below the nominal impedance. However, it may be as much higher as desired. To check this, measure the impedance at all frequencies from 0Hz to over 20kHz, and plot a graph of impedance versus frequency. The curve must not fall below 8 Ohm - 20% at any point.

It follows: You can't measure impedance with an ohmmeter, because that measures with direct current. An impedance meter measures with alternating current of selectable frequency, and is therefore a more complicated and more expensive device.

See also: Impedance in Wikipedia

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