| 摘要 |
An apparatus is provided for determining the mass flow rate of a fluid using thermal means. The apparatus utilizes resistance temperature detectors having substantially linear temperature dependencies to determine the mass flow rate of a fluid. The apparatus maintains a constant ratio between resistances of the first and second resistance temperature detectors, the amount of current necessary to maintain the constant ratio corresponding to the mass flow rate of the fluid. The apparatus includes a microprocessor wherein an algorithm relating the current and mass flow rate including thermophysical properties of the fluid, sensor thermal resistance, and probe stem loss information provides the fluid mass flow rate based upon calibration information. Operation in alternate fluids without the need for recalibration is possible utilizing calibration constants obtained in the primary fluid and substitution of thermophysical properties and stem loss characteristics of each fluid in which operation is desired.
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