Mass flow control systems and methods for controlling the mass flow rate of a gas through a primary conduit are disclosed. One mass flow control system includes a primary conduit for directing a flow of a gas and an adjustment system configured to divert a portion of the gas from the primary conduit to a secondary conduit and provide an adjustment signal that changes when a composition of the gas changes. A mass flow controller is operatively coupled to the primary conduit to control a primary flow rate of the gas. The mass flow controller includes a valve to control the primary flow rate of the gas and a control loop configured to receive the adjustment signal and control the valve to provide the primary flow rate of the gas at a set point.

An automated liquid inventory monitoring and inventory reconciliation system. The system uses a liquid densitometer to precisely measure the density of liquid being dispensed. This allows the system to account for the significant temperature-induced volume variations existing in common liquids such as gasoline. In the preferred embodiments, a fuel inventory processor tracks the quantity of fuel loaded into the tank and the quantity of fuel dispensed to maintain an ongoing computation of the quantity of fuel that should be present in the tank. An accurate tank depth measurement device is also employed. The processor compares the tank depth measurement to the computed quantity of fuel in the tank and uses the values to create an updated tank strapping chart.

In one aspect, fuel inventory data characterizing a level of fuel stored at a fuel storage facility can be received from a sensor in operable communication with the fuel storage facility. Flow meter data characterizing an amount of fuel dispensed from the fuel storage facility by a fuel dispenser nozzle can be received from a flow meter in fluid communication with the fuel dispenser nozzle and the fuel storage facility. Fuel transaction data characterizing the dispensing of fuel by the fuel dispenser nozzle and the dispensing of the fuel by one or more additional fuel dispenser nozzles in fluid communication with the fuel storage facility can be received. An estimate of meter drift characterizing a change in calibration of the flow meter can be determined based on the fuel inventory data, the flow meter data, and the fuel transaction data. The estimate of meter drift can be provided.

In one aspect, fuel inventory data characterizing a level of fuel stored at a fuel storage facility can be received from a sensor in operable communication with the fuel storage facility. Flow meter data characterizing an amount of fuel dispensed from the fuel storage facility by a fuel dispenser nozzle can be received from a flow meter in fluid communication with the fuel dispenser nozzle and the fuel storage facility. Fuel transaction data characterizing the dispensing of fuel by the fuel dispenser nozzle and the dispensing of the fuel by one or more additional fuel dispenser nozzles in fluid communication with the fuel storage facility can be received. An estimate of meter drift characterizing a change in calibration of the flow meter can be determined based on the fuel inventory data, the flow meter data, and the fuel transaction data. The estimate of meter drift can be provided.

A multi-chamber rate-of-change flow meter system and methods for operating the same are disclosed. The multi-chamber rate-of-change flow meter system includes a collection of N chambers, means for drawing a gas into or out of the collection of N chambers, N pressure sensors corresponding one of the N chambers, and means for redistributing the gas among the chambers. A measurement module is coupled to the pressure sensors to obtain a rate of change of pressure in each of the chambers due to the redistribution of the gas and calculate a flow rate of the gas flowing into or out of the collection of N chambers based upon the rate of change of pressure in each of the chambers.

Gas distribution apparatus to provide uniform flows of gases from a single source to multiple processing chambers are described. A regulator is positioned at an upstream end of a shared volume having a plurality of downstream ends. A flow controller is positioned at each downstream end of the shared volume, the flow controller comprising an orifice and a fast pulsing valve. Methods of using the gas distribution apparatus and calibrating the flow controllers are also described.

Mass flow verification systems and apparatus verify mass flow rates of mass flow controllers (MFCs) based on pressure decay principles. Embodiments include a location for coupling a calibrated gas flow standard or a MFC to be tested in a line to receive a gas flow from a gas supply; a control volume serially coupled to the location in the line to receive the gas flow; a flow restrictor serially coupled to the control volume; a pump serially coupled to the flow restrictor; and a controller adapted to allow the gas supply to flow gas through the mass flow control verification system to achieve a stable pressure in the control volume, terminate the gas flow from the gas supply, and measure a rate of pressure decay in the control volume over time. Numerous additional aspects are disclosed.

A valve of a first container is opened to remove fluid from the first container into a second container, where the output of the first container is arranged to be above a maximum fluid level of the second container. The valve of the first container is closed based on a fluid sensor indicating that a fluid level in the first container is at a first fluid level. A pump is caused to pump the fluid from the second container to the first container via a flow meter. An indication is received after pumping the fluid which causes the pump to stop pumping the fluid from the second container to the first container based on the indication. An amount of fluid pumped into the first container is determined based on the first fluid level and a second fluid level indicated by the fluid sensor. An indication of total fluid volume measured by the flow meter is compared to the amount of fluid pumped. An indication of accuracy of the flow meter is output based on the comparison.

A system, comprising a first sensor that generates a first output signal representative of a first flow rate measurement in a first flow rate range of a fluid, a second sensor that generates a second output signal representative of a second flow rate measurement in a second flow rate range of the fluid that at least partially overlaps the first flow rate range of the fluid to form a partially overlapping region, a data repository storing a first calibration relationship corresponding to a first condition of the fluid and a second calibration relationship corresponding to a second condition of the fluid, wherein the first calibration relationship and the second calibration relationship correspond to the first sensor, and a processing subsystem that automatically generates a third calibration relationship when the second flow rate measurement falls in the partially overlapping region, wherein the third calibration relationship corresponds to a third condition of the fluid based at least on the first calibration relationship, the second calibration relationship, the first output signal and the second output signal.

A reference volume for use with pressure change flow rate measurement apparatus has an internal structure comprising elements with cross section and length comparable to the cross section and length of adjacent interstitial fluid regions. The reference volume may have one or more heat conduction elements exterior to and in good thermal contact with a corrosion resistant material that defines the internal fluid holding region.