JPS5676008A - Capacity type converter - Google Patents

Abstract

PURPOSE: To generate a pulse width voltage of duty ratio corresponding exactly to a capacity to be measured by a method wherein a voltage of terminals of the 1st and 2nd variable capacitors varying its capacitance in accordance with the capacity to be measured is always maintained equal and it is constituted that the charge of the 1st capacitor and the discharge of the 2nd capacitor are performed in a same circuit alternately.

CONSTITUTION: The capacitors C₁, C₂ are composed of a moving electrode 10 displacing in response to a capacity to be measured and fixed electrodes 11, 12. The potential V₁ of a point P₁ and the potential of a point P₂ are equal by means of switches SW₁, SW₂ and a buffer amplifier OP₁, as a result, terminal voltages of the capacitors C₁ and C₂ are maintained equal. When the potential V₁ of the point P₁ reaches the minimum value L, then, a comparator CO is turned ON to generate a pulse voltage PW and the capacitor C₁ is charged through a resistor R and switches SW₁, SW₂ and further, a voltage VC₁ enters the comparator CO. When the voltage VC₁ reaches the maximum value H, the switches SW₁, SW₂ are changed-over to the pulse off side and the voltage VC₂ is discharged, thus, the comparator CO outputting the width output PW having a duty ratio proportional exactly to the displacement of the object to be measured.

COPYRIGHT: (C)1981,JPO&Japio