Principle Of Operation; Specifications - Omega FMA 5400A User Manual

FIGURE 2-4 CUTOUT DIMENSIONS FOR LCD PANEL MOUNTING
3.

PRINCIPLE OF OPERATION

The stream of gas entering the Mass Flow transducer is split by shunting a small
portion of the flow through a capillary stainless steel sensor tube. The remainder
of the gas flows through the primary flow conduit. The geometry of the primary
conduit and the sensor tube are designed to ensure laminar flow in each branch.
According to principles of fluid dynamics flow rates of gas in two properly sized
laminar flow conduits are related to one another. Therefore, the flow rates meas-
ured in the sensor tube are directly proportional to the total flow through the trans-
ducer.
In order to sense the flow in the sensor tube, heat flux is introduced at two sec-
tions of the sensor tube by means of precision wound heater-sensor coils. Heat
is transferred through the thin wall of the sensor tube to the gas flowing inside. As
gas flow takes place heat is carried by the gas stream from the upstream coil to
the downstream coil windings. The resultant temperature dependent resistance
differential is detected electronically. The measured gradient at the sensor wind-
ings is linearly proportional to the instantaneous rate of flow taking place.
An output signal is generated that is a function of the amount of heat carried by
the gases to indicate mass-molecular based flow rates.
FMA 5400A/5500A Mass Flow Controller Series Max. Flow 10, 50 and 100 L/min
also incorporate a proportionating solenoid valve and Series Max. Flow 200, 500
and 1000 L/min a motorized valve. The closed loop control circuit of the FMA
5400A/5500A continuously compares the mass flow output with the selected flow
rate. Deviations from the setpoint are corrected by compensating valve adjust-
ments, thus maintaining the desired flow parameters.
4.

SPECIFICATIONS

FLOW MEDIUM: Please note that FMA 5400A/5500A Mass Flow Controllers are designed
to work with clean gases only. Never try to meter or control flow rates of liquids.
CALIBRATIONS: Supplied at Standard Conditions (14.7 psia and 70
F
Conditions (0 C and 1.01 bar abs) unless otherwise requested or stated.
ENVIRONMENTAL (per IEC 664): Installation Level II; Pollution Degree II.
7
F
F), or Normal