| 摘要 |
In a mass flow meter comprising two flow sensor units with identical specifications, flow rate deviations between these two flow sensor units are initially measured at various mass flow rates under a circumstance having the same fluctuating factors as those when a mass flow is actually measured. Subsequently, based on these flow rate deviations, a correction value for matching the values of the mass flow rates measured by these two flow sensor units is calculated and stored in a data storage device. Thereafter, when measuring a mass flow rate, a flow rate deviation, from which the influence by the individual difference in the response to a fluctuating factor between these two flow sensor units has been removed, is calculated by correcting a measured value based on the correction value. The existence or non-existence of an occurrence of a malfunction is judged based on whether the flow rate deviation exceeds a predetermined threshold value t or not. |
| 主权项 |
1. A mass flow meter, comprising:
a flow passage through which a fluid flows, a first flow sensor unit which outputs a first signal that is an output signal corresponding to a mass flow rate of said fluid which flows through said flow passage, a second flow sensor unit which outputs a second signal that is an output signal corresponding to a mass flow rate of said fluid which flows through said flow passage, and a first control unit which determines whether there is a malfunction in said first flow sensor unit or said second flow sensor unit based on the extent of a deviation between the intensity of said first signal and the intensity of said second signal, and said first flow sensor unit and said second flow sensor unit have an identical specifications; wherein said first control unit is configured so as to:
flow said fluid through said flow passage at a plurality of different mass flow rates in a predetermined range and at a predetermined temperature and pressure,execute a learning function for each of said plurality of different mass flow rates, in which:
said first control unit measures the intensity of said first signal and the intensity of said second signal,said first control unit calculates a flow rate deviation, which is a deviation between the intensity of said first signal and the intensity of said second signal, and a correction value for correcting the intensity of a signal S, which is one of said first signal and said second signal, to make the absolute value of said flow rate deviation less than a predetermined threshold value d, andsaid first control unit stores said flow rate deviation and said correction value in a data storage device in relation to a mass flow rate at the time of measuring the intensity of said first signal and the intensity of said second signal, andexecute a self-diagnostics function when measuring a mass flow rate of said fluid in said predetermined temperature and pressure after the execution of said learning function, in which:
said first control unit measures the intensity of said first signal and the intensity of said second signal,said first control unit corrects the intensity of said signal S based on said correction value stored in said data storage device,said first control unit calculates a corrected flow rate deviation which is a deviation between the intensity of said corrected signal S and the intensity of a signal M which is one of said first signal and said second signal and a signal other than said signal S, andsaid first control unit judges that there is a malfunction in either one of said first flow sensor unit and said second flow sensor unit when said corrected flow rate deviation is larger than a predetermined threshold value t. |
