Universal Flow Monitors FlowStream FP Series, Руководство пользователя

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FPMAN-1-190214 Page 6
OPERATION
FlowStream flowmeters accurately measure the mass flow rate of most gases. The flow rate is
determined by measuring the pressure drop across a unique internal restriction, known as
Laminar Flow Element (LFE). The restriction is designed such that the gas molecules are forced
into moving in parallel paths along the entire length of the passage for the entire range of
operation of the device. Unlike other pressure-flow measuring devices, the relationship between
pressure drop and flow is
linear in laminar flowmeters.
FlowStream mass flowmeters utilize an absolute pressure sensor along with a temperature
sensor to compensate for density variations of the gas. When combined with the differential
pressure (volumetric flow) output, the mass flow rate of the gas can be determined.
Laminar Flow Illustration
APPLICATIONS
FlowStream flowmeters are designed to work with non-corrosive, non-ionic, clean, dry gases
only. Introduction of liquids to the internal sensors will damage the unit, and the repair is not
covered under warranty. Relative humidity of the gas can be as high as 100%, as long as proper
installation guarantees that no internal condensation will occur. A 50-micron filter and/or dryer
may be required for some applications.
Using FlowStream at Varying Temperatures
Even though
FlowStream flowmeters measure true mass flow, rapid variations in ambient
and/or gas temperature may affect performance. This is due to the time lag of the internal
temperature sensor and the slow heating and cooling of the flowmeter body. It is highly
recommended that through
proper installation the following two objectives be met:

There be minimal difference between gas temperature and ambient temperature;

Rapid temperature variations be avoided.