Apparatus and method for determining the amount of material in a tank

Claim 1

In a system comprising a tank for storing liquid material, sensing means fitted to the tank for sensing liquid level in the tank and providing first output signals, metering means for metering said liquid material and providing second output signals, and processing means having a first input for receiving said first output signals and a second input for receiving said second output signals, said processing means being operative: (a) to store a first set of data values which represent initial estimates of volumetric quantities of liquid in the tank corresponding to predetermined liquid levels in the tank as sensed by said sensing means, said processing means being programmed with an algorithm which employs a mathematical expression for computing said first data values from said first output signals based on the dimensions of the tank, (b) to store a second set of data values derived from said second output signals, said second set of data values corresponding with actual volumetric quantities of metered liquid, which volumetric quantities are related to said predetermined liquid levels, (c) to compare the first and second sets of data values in order to compute errors in the first set of data values with respect to the second set of data values, (d) to vary the data values in said first set, by varying at least one constant in said mathematical expression, so as to cause new data values to be stored and then to be compared with corresponding data values in said second set to determine if there has been any improvement; the new data value being stored where there is an improvement and the old data value being retained where there is no improvement; the first set of data values which contain the improvements then being employed to provide a corrected calibration characteristic for said sensing means, (e) to refine the corrected calibration characteristic by again varying the first set of data values and repeating a process of comparing the first and second sets of data values and storing a fresh set of first data values containing any further improvements, (f) to compute a correlation between the first and second sets of data values, after each comparison, to determine when there is substantially no further improvement in the calibration characteristic, and (g) to store the refined and corrected calibration characteristic.

Claim 5

A method of calibrating sensing means for providing an output depending on an amount of liquid in a tank, the method including the steps of: providing metering outputs which represent volumetric quantities of metered liquid; providing liquid level sensing outputs; computing volumetric quantities of liquid in the tank from a mathematical expression relating the dimensions of the tank to volumetric content and assigning the computed values to the sensing outputs for respective liquid levels; comparing the computed volumetric quantities with actual volumetric quantities derived from the metering outputs; and providing a corrected calibration characteristic for computing volumetric quantities of liquid in the tank from the sensing outputs; varying constants in the mathematical expression and iteratively comparing the volumetric quantities derived from the varying step with actual volumetric quantities derived from the metering output until there is no substantial improvement in the calibration characteristic.

Claim 6

A method of calibrating sensing means for providing an output depending on an amount of liquid in a tank, the method including the steps of: providing metering outputs which represent volumetric quantities of metered liquid; providing liquid level sensing outputs; computing volumetric quantities of liquid in the tank from a mathematical expression relating the dimensions of the tank to volumetric content and assigning the computed values to the sensing outputs for respective liquid levels; comparing the computed volumetric quantities with actual volumetric quantities derived from the metering outputs; and providing a corrected calibration characteristic for computing volumetric quantities of liquid in the tank from the sensing outputs; varying constants in the mathematical expression and iteratively comparing the volumetric quantities derived from the varying step with actual volumetric quantities derived from the metering output until there is no substantial improvement in the calibration characteristic.