Neugeboren O'Dowd PC
Method and apparatus for measuring the temperature of a gas in a mass flow controller
A method and apparatus for measuring the temperature of a gas in a mass flow controller is described. One embodiment derives gas-temperature information from a mass flow sensor of the mass flow controller without relying on a separate temperature sensor. This embodiment supplies a substantially constant electrical current to a thermal mass flow sensor of the mass flow controller, the thermal mass flow sensor being designed to measure a mass flow rate of the gas; measures an input voltage of the thermal mass flow sensor to obtain a present input voltage, the input voltage varying with a temperature differential between a pair of sensing elements of the thermal mass flow sensor; calculates an adjusted input voltage by accounting for a component of the present input voltage that is dependent on the mass flow rate of the gas; and calculates the temperature of the gas based on the adjusted input voltage. In some embodiments, the calculated gas temperature is used to compensate for the variation, with temperature, of an output voltage of the thermal mass flow sensor under a zero-flow condition.
Advanced Energy Industries, Inc.
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Hiroyuki Michael John
Ito Zolock