Temp. compensation system for sound wave propagation distance measurements - using capacitor charging source or discharge circuit having temp. coefft. compensating temp. dependence of propagation time

摘要

A storage capacitor is charged from a source (Q1,R1..R4) upon transmission of the sound waves. The reception of the corresponding echo pulse is used to initiate its subsequent discharge, via a discharge circuit (Q2,R5,R6,D1,D2), with evaluation of the interval between the beginning of the capacitor charging and full discharge of the capacitor. The charging source (Q1,R1..R4) may have a positive temp coefficient and the discharge circuit (Q2,R5,R6,D1,D2) a negative temp coefficient. USE/ADVANTAGE - Precision ultrasonic ranging device, eliminating need for correction stage.