| 摘要 |
1466594 Electro-physical measurement - flow detectors E B WOLSTENHOLME 25 July 1974 [27 July 1973] 32964/74 Heading G1N Apparatus for detecting a change in a flowing fluid, comprises a constriction in the flow-path with a sensor adjacent but outside the narrowest part of the constriction, means being provided to monitor changes in electrical impedance between this sensor and at least one further sensor to indicate the passage of a discontinuity in the fluid. As described to detect air bubbles in blood e.g. for a transfusion capacitor electrodes are arranged around a Venturi constriction in the flow-pipe. The capacitor varies the frequency of an oscillator, which is detected by a frequency-discriminator to operate an alarm circuit. A rate-of-change circuit is connected to the discriminator output to eliminate long-term D.C. drift signals.
|
