Capacitance measuring circuit and method for liquid leak detection by measuring charging time

摘要

A leak detection system and method are disclosed. The capacitance of a leak detection cable is changed by a leaking liquid. A capacitance measuring circuit detects changes in the capacitance of the cable and thereby detects the presence of a leak. The capacitance measuring circuit includes an inverter, a current source, a comparator, and a timer. The inverter inverts a DC voltage to produce a mirror-image invented DC voltage. The current source produces a constant current proportional to the mirror image inverted DC voltage and supplies the constant current to the cable such that the cable is charged. A comparator compares the voltage across the cable to the input voltage and produces a match signal when they are equal. A timer which is responsive to the match signal measures the time required for the cable to be charged. The capacitance of the cable is directly proportional to the charge time.