Capacitive sensing device

摘要

A digital capacitive sensing device comprises: a reference capacitor having a reference capacitance unaffected by a force to be measured; a reference pulse signal generating circuit which generates a reference pulse signal of a frequency corresponding to the reference capacitance; a sensing capacitor having capacitance variable according to the magnitude of the force; a measuring pulse signal generating circuit having a construction similar to that of the reference pulse signal generating circuit and capable of generating a measuring pulse signal of a frequency corresponding to the capacitance of the sensing capacitor; and a differential arithmetic circuit which adds the number of pulses of the reference pulse signal in a predetermined time interval to a set value and subtracts the number of pulses of the measuring pulse signal in a predetermined time interval from the set value. The reference pulse signal generating circuit is capable of compensating a zero point temperature characteristic of a detection value, and the measuring pulse signal generating circuit is capable of compensating a detection sensitivity temperature characteristic.