MEASURING EQUIPMENT EMPLOYING CAPACITIVE SENSOR HAVING NONNEGLIGIBLE RESISTIVE COMPONENT

摘要

PURPOSE: To allow highly accurate measurement of the quantity of specific component in a specimen using a capacitive sensor having nonnegligible resistive component. ;CONSTITUTION: A pulse generating circuit is constituted of a CMOS type Schmidt inverter 11, a pulse frequency determining element, i.e., a fixed resistor R0, connected across the inverter 11, and another pulse frequency determining element, i.e., a capacitive sensor SC having a resistive component Rh, connected between the input side of the Schmidt inverter 11 and the ground through a fixed series capacitor C0. Variation of the quantity of specific component in a specimen is detected based on the variation of impedance of the capacitive sensor SC and then the variation is converted through a pulse generating circuit into a pulse signal having frequency relevant to the quantity of specific component. The pulse output is then processed to detect a frequency and the quantity of specific component corresponding to the detected frequency is calculated.;COPYRIGHT: (C)1994,JPO&Japio