PURPOSE: To accurately measure the flow rate by reducing effect of changes in pressure from the upstream side.
CONSTITUTION: A variable throttling part 40 is provided at an inlet part 11 of the main body 10. The flow rate of a gas flowing through the main body 10 is computed with a microcomputer 42 based on an output of a piezo-electric film sensor 41 and the opening of the variable throttling part 40 is altered properly according to the flow rate of the gas detected by a stepping motor 43. In other words, when the flow rate detected is small, the opening of a fluid passage port 40a is controlled to be decreased and when the flow rate is large, the opening thereof 40a is controlled to be increased. This allows the lessening of the changing range of pressure on the upstream side.
KATO HIDEO
SATO SHINICHI
