An apparatus and method for determining tank contents employs processing means for comparing sensing outputs (e.g. derived from a liquid level sensor (4)) with metering outputs (e.g. derived from a volumetric totaliser connected to a dispenser (2)) in order to determine errors in the sensing outputs and thereby to provide a corrected calibration characteristic. In the preferred embodiment (which applies to a storage tank (1) containing petroleum), the calibration characteristic is refined, in stages, by applying incremental changes to a conversion factor used in determining data values related to the sensing output and by computing correlations to determine an optimum calibration characteristic. A corrected calibration characteristic (stored in a PROM) may be subsequently employed in equipment for displaying tank contents.

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

Method and apparatus for continuously monitoring the volume of liquid in an underground storage tank and producing data for reconciling volume with throughput. This invention provides a set of algorithms and hardware which allows the loss of product caused by equipment failure or pilferage to be determined in one day or less. In order to accomplish this task this system requires a mechanism in each tank which is capable of indicating liquid depth and temperature to a very high degree of accuracy, a water table indicator, data collection equipment for the dispenser metering system, a local computer system for calculating several algorithms and a second computer, either local or remote, which calculates the daily reconciliation and finds the source of any indicated errors. This second computer also provides reports to the tank operator and activates an alarm system in case there is a loss due to a leak in any part of the tank system.

Method and apparatus for continuous tank monitoring

The present disclosure generally relates to a capacitance sensing apparatus equipped with self-calibrating capacity and method of use thereof. The disclosure contemplates the determination using a secondary means of precise fluid levels according to five possible embodiments, and the use of the determined fluid level to recalibrate the capacitance sensing apparatus along its continuous analog level, namely, a variation of the thickness of the insulation of a capacitance sensing apparatus, the variation of the surface geometry of the capacitance sensing apparatus, the use of a dual-probe sensor including a probe with a varied surface geometry, the use of an electromagnetic sensor adjoining the capacitance sensor, and the variation of the electromechanical sensor to serve as a capacitance sensing apparatus. The disclosure also contemplates methods for using the sensing apparatus previously disclosed to measure a fluid level using a self-calibrating capacitance sensing apparatus. Finally, the present disclosure contemplates the use of an improved mathematical method associated with a variability measurement, such as an exponential smoothing method, to determining locally discrete changes in the variability measurement of the capacitance in order to determine a fixed fluid level.

Self-calibrating liquid level transmitter

A method and a system for detecting the level of fluid in a container is provided: The level meter includes first, second and third generally parallel probes being positioned within the container. The first probe includes a first portion that is at least partially covered by an insulating material, and a second generally exposed end. The second probe is generally free of the insulating material and the third probe provides an electrical ground. An electronic unit is operable to measure electrical characteristics of the first and second probes to determine an amount of the second probe which is exposed to a fluid within the container.

Impedance level meter for liquids in tanks

A fluid characterization sensor comprising a plurality of sensor segments is disclosed. Each segment comprises two electrodes, spaced apart so the fluid in the corresponding interval of depth for that segment is positioned between them. Complex current or impedance is measured by exciting one electrode with an AC signal, and measuring the amplitude and phase of the current in the other electrode. After automatically measuring and accounting for pre-determined gain, offset, temperature, and other parasitic influences on the raw sensor signal, the complex electrical impedance of the fluid between the electrodes is calculated from the measured phase/amplitude and/or real/imaginary components of the received electrical current signal and/or the variation of the measured response with variation in excitation frequency. Comparison of measured results with results taken using known fluids identifies fluid properties. Alternatively, measured results are compared to predicted results using forward models describing expected results for different fluids or contaminants.

Automated phase separation and fuel quality sensor

Method and apparatus for deriving a correction factor used in calculating corrected liquid (e.g., fuel) quantity of a tank having a probe capacitance which varies in accordance with the quantity of liquid contained within the tank. The correction factor reduces sensing diode voltage drop errors and stray capacitance errors (affecting the capacitance of the probe) through use of a switchable high/low amplitude Lo-Z oscillator. All oscillator outputs are "low" amplitude relative to the output amplitudes of conventional devices. Signal processing is effected by inputting raw data (both reference and probe-sensed signals) to an analog-to-digital sampling circuit, which raw data are used for deriving the correction factor. The correction factor is then applied to the raw data to determine a corrected liquid quantity indication. Recalibration of the correction factor periodically permits automatic adaption to changing error magnitudes (i.e., changes in the deleterious effects of diode-voltage drop and/or stray capacitance). Additionally, the relative "health" of the component elements of the tank unit is monitored by tracking changes occurring during recalibration of the correction factor. Establishment of a correction factor outside a predetermined range might indicate faulty probe components or other such difficulties. Numerous practical advantages and economies are obtained by the method and apparatus presently disclosed because of the enabled use of an oscillator with a relatively low voltage output (e.g., under 10 volts peak).

Kurt A. Ramsdale

Papers

Capacitive gauging method and apparatus