Richard A Kent

US Patent:

7607823, Oct 27, 2009

Filed:

Mar 2, 2005

Appl. No.:

10/597857

Inventors:

Richard Kent - Norfolk MA, US

Assignee:

Waters Technologies Corporation - Milford MA

International Classification:

G01N 27/20
G01K 1/00
G01K 7/22

US Classification:

374 4, 374 43, 374 45, 374147, 374185, 374163

Abstract:

A system and method for detecting leaks includes a sensing circuit including a first thermistor device adapted to detected a leak upon contact with a liquid, and, a second thermistor device functioning as a reference device. The first and second thermistor devices are driven with a current such that both devices operate in self-heated mode at a temperature above an ambient temperature. A control system controls a drive circuit for maintaining a constant application of power through both devices in response to a voltage monitored at a reference point in the sensing circuit including the reference thermistor. The voltage at a reference point in a portion of the sensing circuit including the first thermistor device is additionally monitored and compared with the voltage at the reference point in the sensing circuit including the second thermistor device. A leak condition is determined on the basis of a comparison result of the ambient temperature.