TDR system and method for detecting leakage of a liquid

Claim 1

An electrical circuit for detecting leakage of a liquid for use with a leak detection cable which changes impedance when contacted by the liquid, said electrical circuit comprising: (a) electrical pulse generator means for generating a single electrical launch pulse, and for transmitting said single electrical launch pulse down the leak detection cable; (b) delay means, responsive to said single electrical launch pulse, for producing a reset signal upon the transmission of said single electrical launch pulse; (c) sensing means, electrically connected to the leak detection cable, for producing a trip signal upon receiving, from the leak detection cable, a reflected launch pulse which exceeds a predetermined threshold; and (d) latch means, connected to said sensing means, for latching upon receiving said trip signal, and for unlatching upon receiving said reset signal, wherein said latching is indicative of a detection of the leakage of the liquid.

Claim 11

A system for detecting leakage of a liquid, said system comprising (a) a plurality of leak detection cables, each of said plurality of leak detection cables having two substantially parallel conductors with a permeable insulator disposed therebetween, each of said plurality of leak detection cables exhibiting a change of impedance when contacted by the liquid; (b) electrical pulse generator means for generating a single electrical launch pulse; (c) switch means, connected to said electrical pulse generator means, for selectively coupling a selected one of said plurality of leak detection cables to said electrical pulse generator means such that said single electrical launch pulse is selectively transmitted down said selected one of said plurality of leak detection cables; (d) delay means, connected to said electrical pulse generator means, for producing a reset signal upon a transmission of said single electrical launch pulse; (e) sensing means, connected to said selected one of said plurality of leak detection cables, for producing a trip signal upon receiving a reflected launch pulse which exceeds a predetermined threshold for said selected one of the plurality of leak detection cables; (f) latch means, connected to said sensing means, for latching upon receiving said trip signal, and for unlatching upon receiving said reset signal; (g) a microcontroller unit including, (1) means for controlling said switch means wherein any one of said plurality of leak detection cables may be selectively coupled to said electrical pulse generator means, (2) means for determining said predetermined threshold for said selected one of the plurality of leak detection cables, (3) means for causing said electrical pulse generator means to generate said single electrical launch pulse, and (4) means for generating a fault status signal in response to a latching state of said latch means; and (h) counter means, responsive to said reset signal and to said reflected launch pulse, for measuring a time difference therebetween, said time difference being indicative of the relative distance of the leakage disposed along said selected one of said plurality of leak detection cables.

Claim 12

A system for detecting leakage of a liquid, said system comprising (a) a plurality of leak detection cables, each of said plurality of leak detection cables having two substantially parallel conductors with a permeable insulator disposed therebetween, each of said plurality of leak detection cables exhibiting a change of impedance when contacted by the liquid; (b) electrical pulse generator means for generating a single electrical launch pulse; (c) switch means, connected to said electrical pulse generator means, for selectively coupling a selected one of said plurality of leak detection cables to said electrical pulse generator means such that said single electrical launch pulse is selectively transmitted down said selected one of said plurality of leak detection cables; (d) delay means, connected to said electrical pulse generator means, for producing a reset signal upon a transmission of said single electrical launch pulse; (e) sensing means, connected to said selected one of said plurality of leak detection cables, for producing a trip signal upon receiving a reflected launch pulse which exceeds a predetermined threshold for said selected one of the plurality of leak detection cables; (f) latch means, connected to said sensing means, for latching upon receiving said trip signal, and for unlatching upon receiving said reset signal; (g) a microcontroller unit including, (1) means for controlling said switch means wherein any one of said plurality of leak detection cables may be selectively coupled to said electrical pulse generator means, (2) means for determining said predetermined threshold for said selected one of the plurality of leak detection cables, (3) means for causing said electrical pulse generator means to generate said single electrical launch pulse, and (4) means for generating a fault status signal in response to a latching state of said latch means; and (h) counter means, responsive to said reset signal and to said reflected launch pulse, for measuring a time difference therebetween, said time difference being indicative of the relative distance of the leakage disposed along said selected one of said plurality of leak detection cables.

Claim 15

A method for monitoring an impedance of each of a plurality of leak detection cables, wherein for each of the plurality of leak detection cables a position of an impedance change is determined and a fault signal is generated in response to the impedance change, said method comprising the steps of: (1) autoreferencing each of said plurality of leak detection cables to establish a predetermined threshold for each of the plurality of leak detection cables; (2) generating a single electrical launch pulse; (3) selectively transmitting said launch pulse down one of the plurality of leak detection cables; (4) generating a reset signal by tapping off and delaying a portion of said single electrical launch pulse; (5) monitoring said one of the plurality of leak detection cables for a reflected launch pulse; (6) comparing said reflected launch pulse to said predetermined threshold for said one of the plurality of leak detection cables, and generating a trip signal when said reflected launch pulse exceeds said predetermined threshold; (7) setting a latch and generating a fault signal in response to said trip signal; (8) resetting a latch in response to said reset signal; (9) measuring a time between steps (7) and (8) and determining, in accordance with said time, the position of the impedance change of said one of the plurality of leak detection cables; and (10) repeating steps (2) through (9) for each of the plurality of leak detection cables.

Claim 16

A method for monitoring an impedance of each of a plurality of leak detection cables, wherein for each of the plurality of leak detection cables a position of an impedance change is determined and a fault signal is generated in response to the impedance change, said method comprising the steps of: (1) autoreferencing each of said plurality of leak detection cables to establish a predetermined threshold for each of the plurality of leak detection cables; (2) generating a single electrical launch pulse; (3) selectively transmitting said launch pulse down one of the plurality of leak detection cables; (4) generating a reset signal by tapping off and delaying a portion of said single electrical launch pulse; (5) monitoring said one of the plurality of leak detection cables for a reflected launch pulse; (6) comparing said reflected launch pulse to said predetermined threshold for said one of the plurality of leak detection cables, and generating a trip signal when said reflected launch pulse exceeds said predetermined threshold; (7) setting a latch and generating a fault signal in response to said trip signal; (8) resetting a latch in response to said reset signal; (9) measuring a time between steps (7) and (8) and determining, in accordance with said time, the position of the impedance change of said one of the plurality of leak detection cables; and (10) repeating steps (2) through (9) for each of the plurality of leak detection cables.