Abstract: 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.

Abstract: A leak detection system and method are disclosed in which an electrical circuit uses time domain reflectometry techniques to monitor one or more leak detection cables for impedance changes which are caused when a cable is contacted by a leaking liquid. The circuit of the system includes an electrical pulse generator means for generating a single electrical launch pulse, and for selectively transmitting the launch pulse down one of the cables. A delay means responsive to the launch pulse produces a reset signal upon the transmission of the launch pulse. A sensing means connected to a selected cable produces a trip signal upon receiving a reflected launch pulse which exceeds one or more predetermined thresholds. A latch means connected to the sensing means latches (sets) upon receiving the trip signal and unlatches upon receiving the reset signal. A counter means which is responsive to the reset signal and the trip signal measures a time difference therebetween.