| 摘要 |
1510085 Fire alarms AMERICAN DISTRICT TELEGRAPH CO 4 June 1976 [5 Feb 1976] 23069/76 Heading G4N A sprinkler flow detector for providing an alarm signal when a predetermined condition of fluid flow exists in a sprinkler system which includes a system side containing fluid under pressure and having at least one inlet and at least one outlet port, the detector comprising a pressure transducer 24 in communication with the system side for translating fluid pressure into an electrical output signal and signal processing circuitry supplied with the transducer output for providing the alarm signal whenever pressure excursions of the fluid exceed at least one predetermined criterion. As described and shown in Fig. 3, the transducer is a linear variable differential transformer type and the processing circuitry consists of a bandpass amplifier 42 having a low frequency cut-off of 0À025 Hertz and a highfrequency cut-off of 1 Hertz and gives an output inversely proportional to pressure, a pressure-drop threshold circuit 44, an integrator 46, a second threshold circuit 48 and an alarm relay 50. Redundant circuitry 42a-48a and an OR circuit 64 are also provided. Thus, if the pressure drops and the threshold level of 44 is exceeded, and if this condition persists for a time determined by integrator 46, alarm relay 50 is energized to operate an alarm, e.g. a lamp. Circuitry is also provided for checking system parameters, and low or high level pressure excursions. As shown in Fig. 3 a comparator 38 compares the pressure signal with low and high reference levels and causes de-energization of a trouble alarm relay 40, via an OR gate 60. An out-of-limit sensor 56 monitors the transducer 24, a supply-level sensor 58 monitors the supply level, and a coil-continuity sensor 62 monitors the coil of the alarm relay 50. Also provided, but not shown in Fig. 3, are means for producing a trouble alarm if a cover of the system is tampered with and means for testing the system. Details of the circuitry of Fig. 3 are described with reference to Figs. 4A and 4B (not shown). |
