Vacuum variable capacitor
- Vacuum variable capacitor
A vacuum variable capacitor uses a high vacuum as the dielectric instead of air or other insulating material. This allows for a higher voltage rating and/or capacitance value using a smaller total volume. In addition to the higher voltage rating a vacuum dielectric greatly reduces the chance of arcing between the plates. There are several different designs in vacuum variables, the most common geometry of the capacitor plates is usually inter-meshed concentric cylinders. The meshed cylinders are contained within a glass or ceramic vacuum envelope, similar to an electron tube. A metal bellows is used to maintain a vacuum seal while allowing positional control for the moving parts of the capacitor.
Common Applications
Vacuum variable capacitors are commonly used in high voltage applications 5000 volts(5kV) and above. They are used in equipment such as high powered broadcast transmitters, Amateur radio RF Amplifiers and large Antenna tuners.
Other Variations
Other variations of vacuum capacitors include fixed value capacitors. Fixed value capacitors are designed very much like the variable versions with the exception of an adjustment mechanism.
Comparison
When compared to other variable capacitors vacuum variables tend to be more precise and more stable. This is due to the vacuum itself. Because of the sealed chamber the dielectric constant remains the same over a wider range of operating conditions. With air Variable capacitors the air moving around the plates may change the value slightly; often it's not much but in some applications its enough to cause undesirable effects. Another common problem with air variables is dust and insects. Dust collected on the plates or a curious insect can raise havoc. A wandering spider is bound to make fireworks with the open frame design used on most air variable capacitors.
Vacuum variable capacitors are generally more expensive than Air Variable Capacitors this is primarily due to their design and the materials used. Although most use copper and glass some may use other materials such as ceramics and metals such as gold and silver. Vacuum variables also vary in adjustment mechanisms which range from course to fine.
Wikimedia Foundation.
2010.
Look at other dictionaries:
Variable capacitor — Rotary variable capacitor A variable capacitor (also known as a variable air condenser ) is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. Variable capacitors are often used in L/C… … Wikipedia
Capacitor — This article is about the electronic component. For the physical phenomenon, see capacitance. For an overview of various kinds of capacitors, see types of capacitor. Capacitor Modern capacitors, by a cm ruler Type Passive … Wikipedia
Capacitor (component) — Practical capacitors are often classified according to the material used as the dielectric, with the dielectrics divided into two broad categories: bulk insulators and metal oxide films (so called electrolytic capacitors ). Capacitor… … Wikipedia
Vacuum tube — This article is about the electronic device. For experiments in an evacuated pipe, see free fall. For the transport system, see pneumatic tube. Modern vacuum tubes, mostly miniature style In electronics, a vacuum tube, electron tube (in North… … Wikipedia
Vacuum — This article is about empty physical space or the absence of matter. For other uses, see Vacuum (disambiguation). Free space redirects here. For other uses, see Free space (disambiguation). Pump to demonstrate vacuum In everyday usage, vacuum is… … Wikipedia
Manifold vacuum — Not to be confused with Vacuum manifold. Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine s intake manifold and Earth s atmosphere. Manifold vacuum is an effect of a piston s… … Wikipedia
Electronic component — Various components An electronic component is a basic electronic element and may be available in a discrete form having two or more electrical terminals (or leads). These are intended to be connected together, usually by soldering to a printed… … Wikipedia
Electronic symbol — Common circuit diagram symbols (US symbols) An electronic symbol is a pictogram used to represent various electrical and electronic devices (such as wires, batteries, resistors, and transistors) in a schematic diagram of an electrical or… … Wikipedia
Crystal radio — Crystal set redirects here. For the Australian rock band, see The Crystal Set. A modern reproduction of an antique crystal set. It is tuned to different stations by moving the sliding contact (right) up and down the tuning coil (red). The device… … Wikipedia
Memristor — Type Passive Working principle Memristance Invented Leon Chua (1971) First production HP Labs (2008) Electronic symbol … Wikipedia
