| 摘要 |
A pneumatic remote sensing device having a passageway, a connecting tube connected to the downstream end of the passageway, and blockage means for preventing or permitting the escape of gas from the downstream end of the connecting tube. The passageway includes a venturi section, and means for detecting the pressure within the venturi section and producing an output signal dependent on that pressure are provided. Gas under a supply pressure can be introduced at the upstream end of the passageway. Thus, so long as the blockage means are open, the gas can flow through the passageway and the connecting tube, and the pressure within the venturi section of the passageway will remain low. However, when the blockage means close and prevent the escape of gas from the downstream end of the connecting tube, the pressure in the venturi section rises rapidly and the detector means produces an output signal indicative of the closure of the blockage means almost instantaneously after such closure occurs. The device is relatively insensitive to changes in gas supply pressure, and can accommodate an extremely wide range of connecting tube lengths without any adjustment.
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