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3. STRUCTURE & OPERATION PRINCIPLE
3.1 Structure
The MFC consists of four basic devices: flow sensor, flow-splitter bypass, control valve and printed circuit
board.
Figure 2. Structure of D07-7K
Structure of D07-7M is basically as same as structure of D07-7A except solenoid valve.
3.2 Operation Principle
The flow sensor that measure the mass flow (it don’t need pressure compensation) is a kind of capillary pipe
temperature difference flow sensor which consists of two dependent resistors winding on the thin-wall capillaries.
As the gas flows through the sensor tube, gas molecules carry heat down the tube from the upstream coil to the
downstream coil, and a temperature difference is produced. The resistance thermometers are parts of a bridge and
amplifier circuit, thus the change in resistance due to the temperature difference results in a 0～5 VDC electric
Printed Circuit Board
Electric Connector
Sensor
Zero Adjustment
Stand
Inlet-Fittings
Outlet-Fittings
Solenoid Valve
Locknut
Base
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