Variable capacitors can be divided into air dielectric variable capacitor and solid dielectric variable capacitor according to their dielectric materials.
1. Air dielectric variable capacitor
The electrode of the air dielectric variable capacitor is composed of two sets of metal sheets. Among the two sets of electrodes, the fixed set is the stator, and the rotatable set is the movable plate. Air is used as the medium between the movable plate and the stator.
When the rotor of the air dielectric variable capacitor is rotated so that it is fully screwed into the stator space, its capacitance is the largest; on the contrary, when the rotor is completely rotated out of the stator space, the capacitance is the smallest.
Air dielectric variable capacitor are divided into air single-connect variable capacitor (referred to as air single-connected) and air double-connected variable capacitor (referred to as air double-connected, which are composed of two sets of moving plates and stators, which can rotate simultaneously on the same axis). Air dielectric variable capacitor are generally used in radios, electronic instruments, high-frequency signal generators, communication equipment and related electronic equipment.
2. Solid dielectric variable capacitor
The solid dielectric variable capacitor is to add mica or plastic (polystyrene and other materials) film as the medium between its moving piece and fixed piece (moving and fixed pieces are irregular semi-circular metal pieces). The shell is transparent plastic. Its advantages are small size and light weight; its disadvantages are loud noise and easy wear.
Solid dielectric variable capacitors are divided into sealed single-connection variable capacitors (referred to as sealed single-connection), sealed double-connection variable capacitors (referred to as sealed double-connection, it has two sets of moving plates, stators and media, which can be coaxially and synchronously rotated) And sealed four-connected variable capacitor (referred to as sealed four-connected, it has four moving, fixed and medium).
Sealed single-connect variable capacitors are mainly used in simple radios or electronic instruments; sealed double-connected variable capacitors are used in transistor radios and related electronic instruments and electronic equipment; sealed four-connected variable capacitors are commonly used in AM/FM multi-band radios