Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1990-05-21
1992-12-29
Ng, Jin F.
Communications: electrical
Condition responsive indicating system
Specific condition
340603, 7386118, G08B 2100
Patent
active
051755300
ABSTRACT:
A non-intrusive liquid flow detection apparatus for detecting liquid flow in a select pipe, the flow generating a sound wave of known frequency and wavelength. The apparatus includes a pair of transducers spaced along the select pipe approximately one-half wavelength apart. In-phase transducer signals are generated for liquid flow through the select pipe, while out of phase transducer signals are generated for flow from remote pipes. Respective band-pass amplifiers receive and amplify the transducer signals passing the portion within a narrow-band corresponding to the known frequency of the flow sound waves. The amplified signals are summed to cancel out of phase signal components attributable to flow through remote pipes. Thus, high amplitude signals are generated only by fluid flow through the select pipe. The real time summed signal is compared to a time-averaged background noise signal to avoid inadvertent triggering from non-fluid flow sounds of similar sound print. When the real time signal is greater than the background signal by a prescribed amount for a pre-specified period of time a liquid flow detection signal is generated to trigger an alarm.
REFERENCES:
patent: 3176513 (1965-04-01), Kriete
patent: 4905897 (1990-03-01), Rogers et al.
Product Engineering, "Calibrated electronic listener hears flow and measures it" Sep. 1969.
Hofsass Jeffery A.
Ng Jin F.
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