Method and system for flow measurement and validation of a mass flow controller
View Patent ↗Systems and methods for flow verification and validation of mass flow controllers are disclosed. A mass flow controller may be commanded to a specified flow and flow measurement commenced. Gas is accumulated in a first volume and while measurements are taken within this volume. Gas may then flow into a second volume while measurements are taken. The various measurements taken during the two intervals may then be used to calculate the flow rate. The flow rate, in turn, may be used to determine the accuracy of the mass flow controller relative to a setpoint. Additionally, these systems and methods may utilize only one volume to perform flow verification by flowing gas into this volume, taking measurements, and calculating the flow rate based only upon this set of measurements.
1. A method of measuring a rate of flow through a flow controller that is operatively connected to a distribution system having a first region and a second region, the first region having a first internal volume and the second region having a second internal volume, wherein fluid communication between the first region and the second region may be operatively allowed and disallowed via a valve, the method comprising acts of:
collecting first data pertaining to the first region during a first interval;
collecting second data pertaining to the first region and the second region during a second interval;
determining the first internal volume based upon the first data, the second data, and the second internal volume; and
calculating the rate of flow based upon the first internal volume and the first data.
2. The method of claim 1 , wherein the act of determining the first internal volume comprises calculating the first internal volume based upon an equation of state.
3. The method of claim 1 , wherein the first data includes a change in pressure over the first interval and the second data includes a change in pressure over the second interval.
4. The method of claim 3 , wherein the act of collecting second data is performed before the act of collecting first data.
5. The method of claim 3 , wherein the act of collecting first data is performed before the act of collecting second data.
6. The method of claim 3 , wherein at least one of the duration of the first interval and the duration of the second interval is a predetermined length of time.
7. The method of claim 3 , wherein at least one of the duration of the first interval and the duration of the second interval is determined based upon at least one of the first data and the second data meeting a condition.
8. The method of claim 1 , wherein determining the first internal volume comprises receiving an input corresponding to the second internal volume.
9. The method of claim 8 , wherein the first data includes a change in pressure over the first interval and the second data includes a change in pressure over the second interval.
10. The method of claim 9 , wherein the act of collecting second data is performed before the act of collecting first data.
11. The method of claim 9 , wherein the act of collecting first data is performed before the act of collecting second data.
12. The method of claim 1 , wherein at least one of the duration of the first interval and the duration of the second interval is determined based upon at least one of the first data and the second data meeting a condition.
13. The method of claim 1 , further comprising an act of determining the second internal volume prior to the acts of collecting at least one of the first data and the second data.
14. The method of claim 13 , wherein the second internal volume is determined empirically.
15. The method of claim 13 , wherein the second internal volume is determined by receiving an input corresponding to the second internal volume.
16. A method of measuring a rate of flow through a flow controller that is operatively connected to a distribution system having a first region and a second region, the first region having a first internal volume and the second region having a second internal volume, wherein fluid communication between the first region and the second region may be operatively allowed and disallowed via a valve, the method comprising acts of:
collecting first data pertaining to the first region during a first interval;
collecting second data pertaining to the first region and the second region during a second interval; and
calculating the rate of flow based on the first data, the second data, and the first internal volume, wherein the first internal volume was previously determined or is received as input.
17. The method of claim 16 wherein the first internal volume was previously determined by:
collecting previous first data pertaining to the first internal volume during a previous first interval;
collecting previous second data pertaining to the second internal volume during a previous second interval; and
calculating the first internal volume based on the previous first data and previous second data.
18. A measurement system for measuring a rate of flow through a flow controller that can be operatively coupled to a fluid distribution system downstream of the flow controller, the measurement system comprising:
an inlet;
a pressure sensor operatively coupled to the inlet;
a valve operatively coupled to the inlet downstream of the pressure sensor; and
a chamber having a known internal volume and operatively coupled to the valve downstream of the valve;
wherein, when the inlet of the measurement system is operatively coupled to the fluid distribution system, the measurement system is:
collects a first data pertaining to a first volume during a first interval, the first volume corresponding to an internal volume of the fluid distribution system and an internal volume of the measurement system that is disposed downstream of the flow controller and upstream of the valve;
collects a second data pertaining to a second volume during a second interval, the second volume corresponding to the internal volume of the fluid distribution system and an internal volume of the measurement system that is disposed downstream of the flow controller; and
determines the rate of flow through the flow controller based upon the first data, the second data, and the known internal volume of the chamber.
19. The measurement system of claim 18 , wherein the first data includes a change in pressure over the first interval and the second data includes a change in pressure over the second interval.
20. The measurement system of claim 18 , wherein the measurement system is operable to collect the second data before collecting the first data.
21. The measurement system of claim 18 , wherein the measurement system is operable to collect the first data before collecting the second data.
22. The measurement system of claim 18 , wherein at least one of the duration of the first interval and the duration of the second interval is determined based upon at least one of the first data and the second data meeting a condition.
23. The measurement system of claim 18 , further comprising:
an outlet operatively coupled to a second valve, the second valve being disposed downstream of the chamber.