Patent ID: 7979165
Filing Date: 2011-07-12
Classification: G01F,G05D,Y10T

Abstract:
1. A mass flow controller having a path for flowing a fluid, comprising a calibrating valve disposed on the most upstream side of said path for opening or closing said path; a mass flow rate control valve mechanism having such a changeable degree of opening that the mass flow rate of said fluid is equal to a set mass flow rate; a tank provided at said path upstream of said mass flow rate control valve mechanism; a means for sensing the mass flow rate of said fluid to output a mass flow rate signal; a means for sensing the pressure of said fluid to output a pressure signal; and a calibration control means for carrying out mass flow rate calibration using said calibrating valve, said tank, said mass-flow-rate-sensing means and said pressure-sensing means, wherein said calibration control means comprises a reference data memory for memorizing the pressure and mass flow rate of said fluid in an initial state as a reference pressure and a reference mass flow rate, and a calibrating data memory for memorizing the pressure and mass flow rate of said fluid after the lapse of time as a calibrating pressure and a calibrating mass flow rate, and wherein a ratio of the product of a decrement of said reference pressure and a volume of said tank to an integral value of said reference mass flow rate or a difference therebetween is defined as a reference comparator Ai, and a ratio of the product of a decrement of said calibrating pressure and said tank volume to an integral value of said calibrating mass flow rate or a difference therebetween is defined as a calibrating comparator Af; and wherein a variation ratio H of Af to Ai is compared with a predetermined value for calibration.