Where c is capacitance, ε is dielectric constant, A is electrode spacing, and D is electrode spacing. In practical application, the required plate capacitance can be calculated according to the required capacitance and electrode spacing. In addition, the calculation of plate capacitance is also related to the dielectric constant of electrolyte or air, and different electrolytes or air will correspond to different dielectric constants.

The plate capacitor is composed of two parallel metal plates as electrodes, with electrolyte or air as the medium between them, and a certain potential difference is generated between the two electrodes through the charging process. The capacitance of plate capacitor is related to the electrode area and the distance between two electrodes, which is inversely proportional, that is, the larger the electrode area or the smaller the distance between two electrodes, the greater the capacitance.

Plate capacitor has the characteristics of simple structure, wide capacity range, wide voltage range and small volume, and is widely used in various electronic circuits, such as phase shifting, filtering, oscillation, pulse shaping, analog multiplier and frequency conversion.

Flat capacitors have the following advantages and disadvantages:

1, advantages

(1) has good linearity and consistency.

(2) Large capacitance per unit area, saving area.

2. Deficiencies

(1) When the ambient temperature, humidity and electric field change, the capacitive screen will drift, resulting in inaccurate operation.

(2) Only objects with bioelectricity can be sensed.