# US 2014/0190579 A1 · System for and Method of Monitoring Flow Through Mass Flow Controllers in Real Time > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0190579 A1 - Document ID: US20140190579A1 - Status: Published application - Kind: A1 - Application number: 14/205,030 - Filed: 2014-03-11 - Published: 2014-07-10 - Earliest claimed: 2012-01-20 - Assignees: MKS Instruments, Inc. - Inventors: Junhua Ding - Web page: https://patentgrep.com/patent/US20140190579A1 ## CPC - G05D 7/0635: {by action on throttling means (G05D7/0688, G05D7/0694 take precedence)} - G01F 1/88: with differential-pressure measurement to determine the volume flow - G01F 15/002: {for gases} - G01F 15/005: {Valves (valves in general F16K)} - G01F 25/13: {using a reference counter} - G01F 25/15: {specially adapted for gas meters (G01F25/11 - G01F25/14, G01F25/17 take precedence)} - Y10T 137/776: Control by pressures across flow line valve - G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A mass flow controller comprises: a first flow meter constructed and arranged to measured flow rate of mass through the mass flow controller; a second flow meter constructed and arranged to measure flow rate of mass through the mass flow controller; a control valve constructed and arranged so as to control the flow rate of mass through the mass flow controller in response to a control signal generated as a function of the flow rate as measured by one of the flow meters; and a system controller constructed and arranged to generate the control signal, and to provide an indication when a difference between the flow rate of mass as measured by the first flow meter and the flow rate of mass as measured by the second flow meter exceeds a threshold. ## Claims ### Claim 1 A mass flow controller for controlling the flow of gas from a source to a target, the mass flow controller comprising: a first flow meter constructed and arranged to measure the flow rate of the mass of a gas through the mass flow controller as a function of thermal sensing mass flow; a second flow meter including a pressure sensor and a structure defining a predefined volume for receiving gas flowing through the mass flow controller, the second flow meter being constructed and arranged to measure flow rate of the mass of the gas through the mass flow controller as a function of measured rate of decay of the pressure of the gas when allowed to flow from a predefined volume; an upstream proportional control valve constructed and arranged to selectively control the rate of flow of gas into the mass flow controller; a downstream proportional control valve constructed and arranged so as to control the flow rate of the mass of the gas from the mass flow controller in response to a control signal generated as a function of a set point and the flow rate as measured by one of the flow meters; and a system processor/controller constructed and arranged to generate the control signal, and to provide an indication when a difference between the flow rate of mass the gas as measured by the first flow meter and the flow rate of the mass of the gas as measured by the second flow meter exceeds a threshold; wherein the pressure sensor, upstream flow proportional control valve and system processor/controller are further constructed and arranged so as to form a closed-loop pressure controller configured to regulate the pressure inside the predefined volume. ### Claim 2 (depends on 1) The mass flow controller according to claim 1, wherein the closed-loop pressure controller is further constructed and arranged so that the upstream proportional control valve can be adjusted so as to let the inside pressure of the predefined volume rise to the upstream pressure of inlet gas sufficiently slow so as to avoid in-rush gas. ### Claim 3 (depends on 2) The mass flow controller according to claim 2, wherein the closed-loop pressure controller is further constructed and arranged so that if there is an upstream pressure disturbance during flow control when the mass flow controller is controlling the flow of gas from a source to a target, the closed-loop pressure controller will automatically adjust the openness of the upstream proportional control valve so as to regulate the pressure within the predetermined volume such that the inlet pressure disturbance effect on the output flow control of the mass flow controller is minimized and the pressure insensitivity performance of the flow control of mass flow controller is improved. ### Claim 4 (depends on 1) The mass flow controller according to claim 1, wherein the closed-loop pressure controller is constructed and arranged so that if there is an upstream pressure disturbance during flow control when the mass flow controller is controlling the flow of gas from a source to a target, the closed-loop pressure controller will automatically adjust the openness of the upstream proportional control valve so as to regulate the pressure within the predetermined volume such that the inlet pressure disturbance effect on the output flow control of the mass flow controller is minimized and the pressure insensitivity performance of the flow control of mass flow controller is improved. ### Claim 5 (depends on 1) A mass flow controller according to claim 1, wherein the structure defining the predefined volume supports one or more of the first flow meter, the second flow meter, the upstream proportional control valve and the downstream proportional control valve. ### Claim 6 (depends on 1) A mass flow controller according to claim 1, wherein the first mass flow meter comprises a thermal mass flow meter, and the downstream proportional control valve is positioned downstream from the thermal mass flow meter. ### Claim 7 (depends on 1) A mass flow controller according to claim 1, wherein the second proportional control valve is positioned upstream from the first proportional control valve, the predefined volume is positioned between the first proportional control valve and the second proportional control valve through which gas can flow; and the mass flow controller further includes a pressure sensor and temperature sensor for respectively generating a pressure signal and a temperature signal representing the temperature and pressure of gas in the predefined volume. ### Claim 8 (depends on 7) A mass flow controller according to claim 7, wherein the predefined volume is within the mass flow controller between the first and second control valve, and the closed-loop pressure controller is constructed and arranged so that (1) the second control valve can be controlled so as to slowly let the inside pressure of the MFC rise to the upstream pressure of the inlet gas in order to avoid in-rush gas; and (2) if there is an upstream pressure disturbance during the flow control period, the closed-loop pressure controller will automatically adjust the openness of the second control valve so as to regulate the pressure within the predetermined volume such that the inlet pressure disturbance effect on the output flow control of the mass flow controller is minimized, so as to improve the pressure insensitivity performance of the flow control of mass flow controller. ### Claim 9 (depends on 1) A mass flow controller according to claim 1, wherein the mass flow controller and the processor/controller are configured and arranged to operate as follows: (a) when the set point at zero the flow control valve is closed, and the second control valve upstream from the flow control valve is opened to allow the gas from the source to fill the predefined volume. Then the second control valve is closed; (b) when a flow set point is changed from zero to a non-zero value, the second control valve is kept close and the flow control valve is opened to regulate the flow Qt measured by the first flow meter to the flow set point; (c) for a predetermined period of time, the mass flow controller verifies the flow rate based on the rate of decay of the pressure signal in accordance with the following relationship: Qv=−V[d(P/T)]/dt wherein Qv is the verified flow rate as determined by the second flow meter; V is the predetermined volume; P is the pressure as measured by the pressure signal; T is the temperature as measured by the temperature signal; and d(P/T)/dt is the first derivative of the ratio P/T; i.e., the rate of change of the ratio P/T. and (d) After the flow verification, the second control valve is opened to let mass flow controller continue the flow control. ### Claim 10 (depends on 9) A mass flow controller according to claim 9, wherein the predetermined period of time is between about 50 ms and 1000 ms. ### Claim 11 (depends on 9) A mass flow controller according to claim 9, wherein the mass flow controller is further configured to compare the verified flow rate Qv, with the flow rate measured by the first flow meter Qt, and wherein a flow error alarm signal is provided if the deviation between Qt and Qv exceeds the threshold. ### Claim 12 (depends on 11) A mass flow controller according to claim 11, wherein the mass flow controller is configured to perform self-calibration based on the measured values of Qv and Qt. ### Claim 13 (depends on 1) A mass flow controller according to claim 1, wherein the first proportional control valve is controlled allowing gas to flow through the mass flow controller as a function of the flow set point flow rate of mass through the mass flow controller so long as the flow set point is non-zero. ### Claim 14 (depends on 1) A mass flow controller according to claim 1, wherein following the setting of the flow set point to zero, the mass flow controller is configured to immediately close the second proportional flow control valve. ### Claim 15 (depends on 1) A mass flow controller according to claim 1, wherein the threshold is user set. ### Claim 16 (depends on 1) A mass flow controller according to claim 1, wherein the threshold is factory set. ### Claim 17 (depends on 1) A mass flow controller according to claim 1, wherein the threshold is set as a function of permissible tolerance in mass flow for the process with which the controller is used to deliver gas. ### Claim 18 A pressure insensitive mass flow controller for controlling the flow of gas from a source to a target, the mass flow controller comprising: a first flow meter constructed and arranged to provide a mass flow signal as a function of a set point and the measured flow of gas through the mass flow controller; a first proportional control valve constructed and arranged to control the flow of gas through the mass flow controller in response to a valve control signal; a system processor/controller constructed and arranged to generate the valve control signal as a function of a set point signal and mass flow signal; a second flow meter including a pressure sensor constructed and arranged to provide a pressure measurement signal representing the measured pressure of the gas flowing through the mass flow controller, the second flow meter being constructed and arranged to provide a second mass flow signal as a function of the measured pressure of the gas; a second, upstream proportional control valve constructed and arranged upstream from the pressure sensor to selectively control the rate of flow of gas into the mass flow controller as a function of the second mass flow signal; wherein the pressure sensor, second upstream flow proportional control valve and system processor/controller are further constructed and arranged so as to form a closed-loop pressure controller configured to regulate the pressure flow into the mass flow controller. ### Claim 19 A mass flow controller for controlling the flow rate of gas from a source to a target, the mass flow controller comprising: a first flow meter constructed and arranged to measure the flow rate of the mass of a gas through the mass flow controller as a function of sensing mass flow; a second flow meter including a pressure sensor and a structure defining a predefined volume for receiving gas flowing through the mass flow controller, the second flow meter being constructed and arranged to measure and verify the flow rate of the mass of the gas through the mass flow controller as a function of measured pressure rate of decay of the gas when allowed to flow from the predefined volume; an upstream proportional control valve constructed and arranged to selectively control the flow rate of gas into the mass flow controller; a downstream proportional control valve constructed and arranged so as to control the flow rate of the mass of the gas from the mass flow controller in response to a control signal generated as a function of a set point and the flow rate as measured by the first flow meter; and a system processor/controller constructed and arranged to generate the control signal and verify the accuracy of the mass flow control of the mass flow controller as a function of the measured pressure rate of decay of the gas allowed to flow from the predetermined volume; wherein the structure defining the predefined volume is a mounting block for supporting at least the second flow meter and the upstream proportional control valve.