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Mica, a mineral, is one of the oldest dielectric materials used in capacitor construction. There are several kinds of mica, with differing properties, but mica is in general very stable electrically, mechanically, and chemically. It has a dielectric constant in the range 5–7. Mica has the interesting property that its crystalline structure is asymmetrical. The binding forces in one plane are quite strong, while the binding forces along the perpendicular plane are very weak. Because of this, it has a distinct layered structure, and it is possible to split or cleave mica into very thin, optically flat, sheets. For capacitors, mica sheets in the range 0.025–0.125 mm or even thinner are used.

Mica capacitors are available with values that range from 1–4700 pF and even up to 1 μF, but they are generally thought of as low value capacitors. Rated voltages are in the range 100–1000 V for standard dipped mica capacitors. Rated voltages for RF transmitting capacitors are up to 10 kV. Given the excellent electrical performance of mica capacitors in general, manufacturers typically market them with close tolerances (1% or better).

Unlike capacitors that use a bulk dielectric made from an intrinsically insulating material, the dielectric in electrolytic capacitors depends on the formation and maintenance of a microscopic metal oxide layer. Compared to bulk dielectric capacitors, this very thin dielectric allows for much more capacitance in the same unit volume, but maintaining the integrity of the dielectric usually requires the steady application of the correct polarity of direct current else the oxide layer will break down and rupture, causing the capacitor to lose its ability to withstand applied voltage (although it can often be "reformed"). In addition, electrolytic capacitors generally use an internal wet chemistry and they will eventually fail if the water within the capacitor evaporates.

Electrolytic capacitance values are not as tightly-specified as with bulk dielectric capacitors. Especially with aluminum electrolytic, it is quite common to see an electrolytic capacitor specified as having a "guaranteed minimum value" and no upper bound on its value. For most purposes (such as power supply filtering and signal coupling), this type of specification is acceptable.

Simple capacitance scales on DMMs just measure the capacitance in uF and do not test for leakage, ESR (Equivalent Series Resistance), or breakdown voltage. If the measurement comes up within a reasonable percentage of the marked value (some capacitors have tolerances that may be as much as +100%/-20% or more), then in many cases, this is all you need to know. However, leakage and ESR frequently change on electrolytic as they age and dry out.

Many capacitance meters don't test anything else but are probably more accurate than a cheap DMM for this purpose. A meter of this type will not guarantee that your capacitor meets all specifications but if it tests bad - very low - the capacitor is bad. This assumes that the test was made with the capacitor removed (at least one lead from the circuit - otherwise other components in parallel can affect the readings.

To more completely characterize a capacitor, you need to test capacitance, leakage, ESR, and breakdown voltage. Other parameters like inductance aren't likely to change on you.

Smaller spark gaps are often used to protect sensitive electrical or electronic equipment from high voltage surges. In sophisticated versions of these devices (called gas tube arresters), a small spark gap breaks down during an abnormal voltage surge, safely shunting the surge to ground and thereby protecting the equipment. These devices are commonly used for telephone lines as they enter a building; the spark gaps help protect the building and internal telephone circuits from the effects of lightning strikes. Less sophisticated (and much less expensive) spark gaps are made using modified ceramic capacitors; in these devices, the spark gap is simply an air gap sawn between the two lead wires that connect the capacitor to the circuit. A voltage surge causes a spark which jumps from lead wire to lead wire across the gap left by the sawing process. These low-cost devices are often used to prevent damaging arcs between the elements of the electron gun(s) within a cathode ray tube (CRT).

Suntan ( www.suntan.com.hk ) has supply Spark Capacitors .The Spark Capacitors - TS21 features are: Spark gap capacitors are designed to provide a reliable discharge path for stray, transient over voltages and static voltage build-up. The construction of the spark gap enable the circuit designer to reduce cost by specifying lower voltage components with the assurance that over-voltage conditions will be prevented.

Suntan Technology Company Limited
----All Kinds of Capacitors

Electric Double Layered Capacitors , know as “Gold Capacitor”, offer the highest volumetric efficiency of all capacitor technologies. It is often compared to a secondary battery. Unlike batteries, the Gold Capacitor does not rely on a chemical reaction to produce electric current rather it is a storage cell that utilizes the absorption/release reaction of ions.

Compared to other capacitors and batteries,Gold Capacitors are very new. We have summarized the characteristics and reliability of Gold Capacitors in this manual. Suntan has developed the Gold Capacitor to meet your design needs. We hope you will find this manual informative and useful. Any requirements please visit www.suntan.com.hk.

The polypropylene is sometimes used when a higher tolerance is necessary than polyester capacitors offer. As the name implies, this capacitor uses a polypropylene film for the dielectric. One of the advantages of the capacitor is that there is very little change of capacitance with time and voltage applied. They are also used for low frequencies, with 100 kHz or so being the upper limit. They are generally only available as leaded electronics components.

Such as our polypropylene film capacitors , it has three features:

1. Comparatively small size saves space of print circuit board.

2. Temperature dependence indicates characteristic of negative.

3. Dissipation Factor is normally low and temperature dependence of capacitance is linear.

A varistor is an electronic component with a significant non-ohmic current-voltage characteristic. The name is a portmanteau of variable resistor. Resistors are the most widely used components in electronic circuits. Although very simple in concept they are key to the operation of many circuits. They can be used in a variety of ways to produce the required results.

When designing or building an electronic circuit, it may be necessary to use two or more resistors instead of one. Either the correct value of resistor may not be available, or it may be necessary to dissipate a higher power than that which a single resistor can dissipate on its own.

Ceramic capacitors are the workhorses of the capacitor world these days. Ceramic capacitors are used in millions as a result of a combination of their cost and performance. There is a wide variety of dielectrics that can be used, but as the name of the ceramic capacitor suggests, they are all ceramic in nature.

In order to ensure that sufficient levels of capacitance can be obtained within a single capacitor package, ceramic capacitors, like types of capacitor have multiple layers. This increases the level of capacitance to enable the required values of capacitance to be achieved.

This type of capacitor is a essentially a form of Polyester Film Capacitor where the Polyester Films themselves are Metallized. The advantage of using this process is that because their electrodes are thin, the overall capacitor can be contained within a relatively small package. The Metallized Polyester Film Capacitors are generally only available as leaded electronics components.

Suntan is a Hong Kong based manufacturer of Plastic Film Capacitors, including Green Polyester Film Capacitor, Metallized Polyester Film Capacitor, Mini BOX Metallized Film Capacitor, X2 Capacitor, Metallized Polyester Film Capacitor and Polystyrene Film Capacitor etc.

The most common form of leaded tantalum capacitors in use today are the "solid" tantalum capacitors. They offer particularly small package sizes and as a result they have been widely used in many areas of electronics.

Leaded tantalum capacitors (solid tantalum variety) are generally small and encapsulated in epoxy to prevent damage. The capacitor marking may be written directly onto the encapsulation as figures, although many used a color coding system.

Warning: - In view of the nature of these capacitors, great care should be taken not to stress these capacitors. The polarity should not be reversed, nor should they be exposed to over-voltage conditions - even spikes. If they are exposed to these conditions then they may fail, sometimes exploding.