CAPACITIVE DYNAMIC QUANTITY SENSOR

摘要

PROBLEM TO BE SOLVED: To stably and linearly convert the dynamic displacement detected by means of a capacitive sensor into a voltage (DC output) without being subject to the influence of a stray capacitance by using a driving frequency for high- speed detection without being restricted by the responsiveness of an operational amplifier. SOLUTION: When a capacitance element 5 (Cs) for detecting dynamic quantity is displaced in proportion to a dynamic quantity, the balance between the amount of charges in the element 5 and the that of charges in another capacitance element 4 for reference is destroyed and a difference occurs between the amounts. When the difference occurs, the output Vout of an operational amplifier 7 changes in proportion to the difference, but the output Vout finally stabilizes at the point at which the amounts of charges in the elements 5 and 4 become equal to each other. The output Vout is proportional to the inverse number of the capacitance Cs of the element 5 and takes the form of a DC voltage. In addition, such an output that does not rely upon an integrated feedback capacitance (feedback capacitor) CF can be obtained.