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What Is Capacitive Coupling?

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  • Written By: Alexis W.
  • Edited By: Heather Bailey
  • Last Modified Date: 30 March 2014
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    Conjecture Corporation
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Capacitive coupling is referred to in electronics as the transfer of a common energy to different devices linked together through an electrical network. The transfer of energy is done by using different capacitors between circuits. It may also be done in sequence to the original power signal that is intended for coupling.

In an analog circuit, the purpose of capacitive coupling is to interrupt a DC circuit, which is why the capacitor used is referred to as a DC-blocking capacitor. In digital circuits, capacitive coupling is most often used in different types of communications devices as a way to block any chance of interference with a signal or to avoid the formation of any type of voltage or power imbalance. These imbalances are often associated with signal amplifiers, especially when the input and output leads couple, which causes what users might hear as feedback.

Capacitive coupling can also occur unintentionally, when a circuit has a frequency running through it and another wire is close in proximity. In such cases, the powered wire may couple with the wire that is projecting bandwidth or frequency and either intercept or simply interfere with the signal of the original wire. The opposite can also occur, wherein the powered wire interferes with the frequency, causing noise or interference with the incoming signal being processed.

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When the capacitive coupling occurs on an unintentional basis, usually because two wires powered at different bandwidths or voltages are too close to each other, an unwanted effect called electrical noise occurs. This noise may manifest in either signal interruption of the product’s incoming or outgoing signal or background noises such as high-pitched hissing. Alternatively, the product may simply not work the way it was originally intended. When this occurs in the manufacturing process, most product manufacturers correct the problem by either separating the wires in the wiring schematic or by creating a nonconductive wall between the two wires.

When a coupling effect is desired in an electrical bandwidth device, however, the two wires that would typically be separated are placed within a close proximity of each other. It may also be planned in the schematic that the two wires wind around each other to create the environment where the highest amount of coupling is desired. When the coupling effect is desired between both digital or analog circuits, they are coupled together through the use of capacitors that function separately, depending on whether the signal being powered is digital or analog.

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Discuss this Article

hamje32
Post 4

The article was very illuminating. I’ve had audio equipment like microphones hooked up to my video equipment, and with other wires nearby, I’ve experienced hissing and background noise like the article says.

I knew that this was interference of some sort but didn’t know that it was capacitor related.

MrMoody
Post 3

@miriam98 - I can’t say much about wind and solar. The little that I know about capacitors comes from the wonderful world of automotive audio equipment.

I installed audio equipment and had to hook up to a power capacitor. This capacitor stores the electricity from the battery, and let me tell you, it charges very quickly.

I imagine that a bunch of these strung together in a coupled fashion would form a bank and could store more charge. I don’t know how long the charges last, though, either individually or coupled together. I’m sure there are formulas for figuring that stuff out.

miriam98
Post 2

@allenJo - That’s informative. I’ve never looked into the details of what the survivalists need to keep themselves going, besides solar panels, but I guess it would make sense that you would need some kind of a charging system for that kind of an arrangement.

I wonder if that’s the way that windmills store electricity too. That so far is the biggest hurdle, from what I understand, to widespread adoption of solar and wind power – the question of how to store the energy.

I had always heard that batteries were used but I didn’t know much more than that, or how long the batteries would last on their charge.

allenJo
Post 1

Sometimes when I surf the Internet I come across these websites of survivalists who dream of “living off the grid.”

What they mean is that they want to generate their own energy, grow their own food, capture sunlight, be completely self-sustaining.

I don’t know if it’s really doom and gloom that they fear, or just the thought of being totally independent that truly motivates them.

However, after reading this article I am reminded of one arsenal in the survivalist’s toolkit. The capacitor bank is basically a bunch of capacitors coupled together.

It has the ability to store a lot of energy in a way that a single capacitor could not. If you were capturing energy through solar power or wind, you could store it in a capacitor bank so that when the sun isn’t shining and the wind isn’t blowing, you’d still have power.

That’s one application of this technology I suppose that would be very useful.

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