What is the Variable capacitor?

The Variable capacitor is a capacitance that can be adjusted within a certain range of capacitors, when changing the relative effective area between the pole plate or the distance between the pole plate, its capacitance changes, usually used as a radio receiver circuit tuning capacitor, mainly air dielectric variable capacitor and solid dielectric variable capacitor two kinds of capacitors, widely used in tuned amplification, frequency selection oscillation circuit.

Capacitor Identification

The capacitance value of a capacitor is identified on the body of the capacitor by a number or alphanumeric combination, or sometimes by a ribbon. Capacitor labels give various parameters of the capacitor, including capacitance value, voltage rating, and tolerance.

Some capacitors do not have capacitance units; in these cases, they are defaulted from the given value and determined empirically. In some cases, a 3-digit representation is used. The first two digits are the first two digits of the capacitance value, and the third digit is the multiplier or the number of O's following the second digit. For example, 103 indicates 10,000 pF.

Some types of capacitors use WV or WVDC to indicate the rated voltage, others omit it. When omitted, the voltage rating can be determined from information provided by the manufacturer. Capacitor tolerances are usually expressed in percent, e.g., ±10%. Temperature coefficients are expressed in parts per million (ppm). Such markings consist of a P or N followed by a number. For example, N750 indicates a negative temperature coefficient of 750 ppm /°C, while P30 indicates a positive temperature coefficient of 30 ppm /°C. The NPO marking indicates that both the positive and negative temperature coefficients are O so that the capacitance value does not vary with temperature. Also, certain types of capacitors are marked with coloured ribbons

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