Onicon F-2600 Uživatelský manuál stáhnout pdf (Strana 13)

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F-2600 & F-2700 Vortex Flow Meter Manual 02/15 - 0808-7 / 19204 Page 13

1.2 HOW THE ONICON VORTEX MASS FLOW METER OPERATES

Figure 1. In-Line Multi-Parameter Vortex Mass Flow Meter

ONICON F-2600 Series & F-2700 Series Vortex Mass Flow Meters use a unique sensor

head to monitor mass ow rate by directly measuring three variables. uid velocity,

temperature and pressure. The built-in ow computer calculates the mass ow rate

and volumetric ow rate based on these three direct measurements. The sensing head

is built into the vortex meter’s ow body. To measure uid velocity, the ow meter

incorporates a bluff body (shedder bar) in the ow stream and measures the frequency of

vortices created by the shedder bar. Temperature is measured using a platinum resistance

temperature detector (PRTD). Pressure measurement is achieved using a solid-state

pressure transducer. All three elements are combined into an integrated sensor head

assembly located downstream of the shedder bar within the ow body.

1.2.1 Velocity Measurement

ONICON’s vortex velocity sensor is a patented mechanical design that minimizes the

effects of pipeline vibration and pump noise, both of which are common error sources

in ow measurement with vortex ow meters. The velocity measurement is based on the

well-known Von Karman vortex shedding phenomenon. Vortices are shed from a shedder

bar, and the vortex velocity sensor located downstream of the shedder bar senses the

passage of these vortices. This method of velocity measurement has many advantages

including inherent linearity, high turndown, reliability and simplicity.

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Onicon F-2600 Uživatelský manuál Strana 13