The invention relates to an annular
variable capacitor and an application thereof, and belongs to the technical field of electromagnetic touch induction. The annular
variable capacitor comprises a pen shell and a large-capacity pen refill assembled in the pen shell, and is characterized in that the
tail end of the pen refill is closely contacted with an axial
variable capacitor capable of expanding and contracting in the axial direction, and the axial variable
capacitor is used for detecting
axial pressure of the pen refill; an annular variable
capacitor which is tightly nested between the outer side of the front half part of the pen refill and the inner side of the pen shell is used for detecting
radial pressure of the pen refill; two electrodes of the annular variable
capacitor are an inner
electrode nested at the outer side of the pen refill and an outer
electrode abutted inside the pen shell, a deformable elastic medium is arranged between the two electrodes, and the center of the inner
electrode deviates when the pen refill moves along the radial direction; and the axial variable capacitor and the annular variable capacitor are arranged in parallel. According to the invention, both radial sensitivity detection and axial sensitivity detection are satisfied through a method of additionally arranging the annular variable capacitor at the outer side of the pen refill, so that replacement of a light small-capacity pen refill for a large-capacity pen refill is enabled to be possible in the field of electromagnetic touch induction.