`Principle of setting a triangular prism acetylene flowmeter vortex body fluid, from the vortex of both sides alternately produce two columns regular vortex, the vortex is called Karman vortex street, as shown in (a) below. Load capacitance detection probe or piezoelectric detection probe in the vortex shedder in and the corresponding matching circuit, can constitute a capacitance detection type acetylene flow meter / sensor or piezoelectric detection of acetylene-type flowmeter. Figure (a) listed in the vortex shedder vortex downstream arranged asymmetrically. Set the frequency of the vortex is f, the average speed measured medium to flow is V, the vortex shedder welcome stream surface width d, table body diameter is D, based on the principle of Karman vortex street, there is the following relationship: f = St.V / [(1-1.25d / D) d] where: f- Karman vortices occur resulting frequency side of the average velocity d- St- Strouhal number V- fluid flow cylinder surface width D- pipe diameter Figure (b) in the curve table St = straight section 0.17, the frequency and velocity is proportional to the release of the vortex, namely acetylene flow meter measuring range of the sensor. As long as the detected frequency f can be obtained within a tube of fluid flow rate, volume flow rate calculated by the velocity V. Second, the acetylene flow meter installation requirements: 1, acetylene flow meter can be installed indoors or outdoors. When installed in ground wells, and there is the possibility of flooding, you should choose submersible sensor or transmitter. 2 ~ acetylene flowmeters horizontal, vertical or inclined installation in the pipeline, but when measuring liquids, the pipeline must be filled with liquid. Therefore, acetylene flow meter installed in a vertical or inclined pipe flow direction of the liquid should be from the bottom up. 3, the upstream and downstream sides of the acetylene flow meter should be left long straight pipe upstream and downstream straight pipe length requirements with piping conditions vary. Upstream acetylene should avoid installing the meter control valve or half open valves or valve should be installed after the half-open valve downstream of the meter 5D. 4, the installation of acetylene meter pipe diameter must be consistent with the meter diameter, otherwise it must be adjustable. 5, in the design of the pipeline, the upper end of the sensor or transducer should stay at least 500mm of space to facilitate debugging and maintenance.