A leak detector includes an off-center mounted metering pin cooperating with a single cross-hole in a poppet valve to accommodate adjustment of the flow rate past the metering pin by rotating the poppet valve about its longitudinal axis. A flow director, cooperating with the poppet valve, directs all flow into the leak detector directly into the line during initial flow into the leak detector. A piston, responsive to line pressure, is sized smaller in diameter than the poppet valve to cause the line pressure to increase rapidly and significantly during the leak sense mode and which size permits reduction in size and weight of the leak detector.
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and includes a disclosure contained in a provisional application entitled "LEAK DETECTOR" filed Feb. 22, 2000, and assigned Ser. No. 60/184,084, and this application is a continuation application of an application entitled "LEAK DETECTOR", filed Feb. 29, 2000, assigned Ser. No. 09/515,002 now U.S. Pat. No. 6,269,678, issued Aug. 7, 2001, all of which applications are assigned to the present assignee.
Measurements are obtained by a computing unit based on an output Vh from an indirectly-heated constant-temperature controlling flow rate measuring section (16) and an output Vout from a two-constant-point temperature difference detecting flow rate measuring sections (18a, 18b). In the flow rate measuring section (16), a heating element (163) is feedback-controlled based on a detected temperature by a heat sensing element (162) to obtain an output Vh based on the feedback-controlled condition. An output Vout is obtained from flow rate measuring sections (18a, 18b) based on the detected temperature difference between a heat sensing element (182) disposed on the liquid-flow-direction upstream side of the flow rate measuring section (16) and a temperature sensing element disposed on the downstream side. A computing unit outputs as a measurement a flow rate obtained based on the output Vh in a flow rate region where a flow rate is larger than a predetermined boundary flow rate, and outputs as a measurement a flow rate obtained based on the output Vout in a flow rate region where it is less than a boundary flow rate. Accordingly, a flow rate is measured with good precision and sensitivity over a wide flow rate range from a trace-amount flow rate region to a comparatively large flow rate region.
