초록 ▼

A system and method for operating a mass flow controller is described. One embodiment validates the operation of a mass flow controller thermal sensor, including detecting zero drift and span drift in the sensor by comparing the thermal sensor output to a pressure sensor output. In one embodiment, e

A system and method for operating a mass flow controller is described. One embodiment validates the operation of a mass flow controller thermal sensor, including detecting zero drift and span drift in the sensor by comparing the thermal sensor output to a pressure sensor output. In one embodiment, each sensor provides a signal to a digital controller or other processing unit and the controller calculates the mass flow rates of a gas flowing through the unit as measured by the sensors. The mass flow rates may then be compared to determine if one of the thermal sensor is operating properly.

대표청구항 ▼

What is claimed is: 1. A method of operating a mass flow controller comprising, directing a portion of gas flow from a main flow line through a first tube, the first tube having a center portion, the center portion coupled to a first sensor; coupling a second tube comprising a second-tube-proximal-

What is claimed is: 1. A method of operating a mass flow controller comprising, directing a portion of gas flow from a main flow line through a first tube, the first tube having a center portion, the center portion coupled to a first sensor; coupling a second tube comprising a second-tube-proximal-end and a second-tube-distal-end to the main flow line so that the second-tube-proximal-end is coupled to an upstream-main-flow-line-portion and the second-tube-distal-end is coupled to a second sensor; coupling a third tube comprising a third-tube-proximal-end and a third-tube-distal-end to a main flow line, the third-tube-proximal-end coupled to a downstream-main-flow-line-portion and the third-tube-distal-end coupled to the second sensor; processing a first signal from the first sensor; processing a second signal from the second sensor; sending the first and second signals to a digital controller; using at least one of the first and second signals to (i) operate a control valve and (ii) validate the proper operation of the mass flow controller. 2. The method of claim 1 wherein, directing a flow of gas from a main flow line through a first tube comprises, creating a pressure differential across a mass flow controller bypass, coupling a proximal end of a first tube to a high gas pressure flow section upstream of the bypass, and coupling a distal end of a first tube to a low gas pressure flow section downstream of the bypass; coupling a second-tube-proximal-end to an upstream-main-flow-line-portion comprises coupling the second-tube-proximal-end to the high gas pressure flow section; and coupling a third-tube-proximal-end to a downstream-main-flow-line-portion comprises coupling the third tube proximal end to the low gas pressure flow section. 3. The method of claim 1 wherein, using at least one of the first and second signals to validate the proper operation of the mass flow controller comprises, using a thermal sensor to output the first signal; utilizing the first signal to calculate a first mass flow rate; using a pressure sensor to output the second signal; utilizing the second signal to calculate a second mass flow rate; and comparing the first and second mass flow rates. 4. The method of claim 1 further including, determining whether thermal siphoning is occurring in the mass flow controller; and extending an operational range of the mass flow controller beyond a laminar flow. 5. The method of claim 4 wherein, determining whether thermal siphoning is occurring in the mass flow controller comprises, using the second signal to calculate a real-time pressure differential across the mass flow controller bypass; and comparing a present pressure differential reading to a past pressure differential reading to determine if thermal siphoning is occurring. 6. The method of claim 4 wherein, extending an operational range of the mass flow controller comprises, controlling the mass flow rate of a turbulent gas flow through a mass flow controller.