| 摘要 |
A valve arrangement includes a variable aperture through which fluid may flow, a closure element adjustable to vary the size of the aperture, and a sensor unit which generates an output signal dependent on the aperture size. The sensor unit has a light detector disposed downstream of the aperture to detect light passed through the aperture and to generate the output signal dependent on the detection of the light. This signal is supplied to a visual display unit having indicators that are respectively activated to show if the valve is open or closed.
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