| 摘要 |
A flow rate sensor includes a diaphragm operated switch coupled to a Venturi in a flow conduit. The apparatus includes a housing having a diaphragm defining a chamber. The chamber has a first port connected to the Venturi and a second vent port. A valve connected between the first port and the diaphragm is spring loaded so that the first port is normally open. In the absence of fluid flow, the Venturi pressure is zero under the diaphragm and the diaphragm is at rest in an up position so that the valve is open. With fluid flow through the Venturi, vacuum will build under the diaphragm so that the diaphragm will travel down until the valve closes the first port. With the valve closed, pressure under the diaphragm will increase due to flow through the vent port and the diaphragm will move up. The valve will remain closed until the diaphragm up stroke is equal to the valve stem lost motion. The valve will then open and the process will cycle so that the diaphragm oscillates at a rate that bears a relationship to the square of the fluid flow rate through the Venturi. A sensor coupled to the diaphragm produces a pulsating digital signal, from which signal the flow rate may be calculated.
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