System and method for improving the accuracy of a rate of decay (ROD) measurement in a mass flow controller

A method of manufacturing a mass flow controller, the method comprising:

• providing a block to secure components of the mass flow controller;
• forming a conduit comprising a fluid inlet and a fluid outlet to define a fluid flow path;
• providing an inlet block comprising an inlet passage, an inlet channel fluidly coupled to the fluid inlet, and a reservoir fluidly coupled to the inlet channel upstream from a location at which the inlet channel is fluidly coupled to a bypass of the conduit, wherein the reservoir is sized and configured, based on operating conditions, to enable a rate of decay measurement to be performed without interrupting the flow of fluid to the fluid outlet, and wherein the inlet block is formed from a single piece of material;
• providing filler material within the reservoir;
• providing at least one flow sensor that generates a flow sensor signal proportional to the flow rate of fluid through the conduit;
• providing at least one pressure sensor that generates a pressure sensor signal that is indicative of the pressure of the fluid within the conduit, coupling the at least one flow sensor and the at least one pressure sensor to a control subsystem that is operable to
• receive the flow sensor signal and generate a flow sensor based flow rate for the fluid;
• and coupling a valve assembly to the block and establishing a communicative coupling between the control subsystem and the valve assembly, wherein the control subsystem is operable to control the valve assembly to adjust the rate of fluid through the conduit.

A mass flow controller, comprising:

• at least one conduit comprising a fluid inlet and a fluid outlet, the conduit defining a flow path along which the fluid flows;
• an inlet block comprising an inlet passage, an inlet channel, and a reservoir fluidly coupled to the inlet channel upstream from a location at which the inlet channel is fluidly coupled to a bypass of the conduit, wherein the reservoir is configured, based on the operating conditions of the fluid, to facilitate a rate of decay measurement of the pressure of the fluid within the conduit while the mass flow controller is operational, and wherein the inlet block is formed from a single piece of material;
• wherein filler material is disposed within the reservoir;
• at least one pressure sensor that generates a pressure sensor signal that is indicative of the pressure of the fluid within the conduit, the at least one pressure sensor being coupled to a controller that is operable to generate a pressure sensor based pressure
• measurement for the fluid, the pressure sensor based pressure measurement being determined at least in part from the pressure sensor signal;
• at least one flow sensor that generates a flow sensor signal indicative of a flow rate of the fluid through the conduit, the at least one flow sensor being coupled to a controller that is operable to generate a flow sensor based flow rate for the fluid, the flow sensor based flow rate being determined at least in part from the flow sensor signal;
• a control subsystem coupled to the at least one flow sensor;
• and
• a valve assembly communicatively coupled to the control subsystem and operable to adjust the rate of fluid through the conduit.