基本信息
摘要：1494636 Measuring fluid-flow rate electrically ELEKTRONIK-KONSTRUKTIONER AB 2 Dec 1974 [3 Dec 1973] 52105/74 Heading G1N A flow measuring or monitoring device comprises a pair of similar temperature sensors, each comprising a monolithic semi-conductor crystal, one of which is associated with a heater arranged to heat it by a constant amount and means for comparing the outputs of the sensors to obtain flow velocity. The device may be used to operate an alarm when flow velocity deviates from a desired value. The sensors 8, 10 may be arranged on a sheet 6 projecting into the fluid stream with its plane parallel to the direction of flow. A radiation shield 12 is sited between them and circuitry and an alarm may be contained in a unit 4 on the exterior of the conduit wall 2. Each sensor 8, 10 may comprise an identical array of four bi-polar transistors T3, T4 Fig.3, integrated on the same silicon wafer, three being connected, as shown, and one 18 being used as a heater in the sensor 10. The corresponding one in the sensor 8 is not utilized. Heater current is supplied to drive the transistor 18 in the reverse direction, by a conventional stabilized voltage assembly I with potentiometer R6 providing for voltage adjustment. Capacitor C2 is a noise filter. The sensor circuit includes a potentiometer R13 for the sensor 8 for voltage adjustment and potentiometers R10, R14, the former for fine adjustment in temperature compensation for the sensor 10 and to account for manufacturing tolerances between the sensors and the latter to adjust the point at which an alarm indicates that flow has deviated from the desired flow valve. Capacitor C3 is a noise suppressor and also forms the shield 12. The two diode paths are connected to a level discriminator IC2 and to a relay Rel which energizes the alarm. The sheet 6 carries some of the circuitry in printed form. The device may be used to regulate flow rather than operate an alarm. Uses described relate to air-flow control.
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