| 摘要 |
The unknown amount or mass of liquid contained in a storage tank is measured by calibrating the tank in an empty and partially full condition. The calibration includes measuring the mass of the empty tank, and is accomplished by applying a measured amount of heater power or energy to the tank and its contents, and measuring the temperature response to determine the product of total mass multiplied by specific heat. The specific heat depends upon the mass or amount of liquid in the tank, but a linear relationship is established between total mass and the product of total mass times specific heat. The unknown mass of liquid is then determined by applying a known amount of heater power or energy to the tank and its contents, and measuring the temperature rise or rate of rise in response thereto. The mass of the system multiplied by specific heat is determined from the temperature rise or rate of rise, and is interpolated or extrapolated relative to the calibration to determine the mass of the system with its unknown amount of liquid. The mass of the tank is subtracted from the unknown system mass to determine the mass of the liquid. In a spacecraft fuel tank application, the tank-empty calibration is performed in an evacuated test chamber, and the partially-full calibration is performed on-orbit after one thruster burn has consumed an amount of fuel which is determined from a schedule based upon knowledge of the consumption of the particular thrusters or types of thrusters being used.
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