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The output of a capacitance fuel sensor is supplied to two switches that are controlled by a switching control unit. The two switches are opened and closed in synchronism and antiphase with one another, and in quadrature with the drive voltage applied to the sensor. The output of one switch is suppl

The output of a capacitance fuel sensor is supplied to two switches that are controlled by a switching control unit. The two switches are opened and closed in synchronism and antiphase with one another, and in quadrature with the drive voltage applied to the sensor. The output of one switch is supplied to the input of a first integrating current-to-voltage amplifier which in turn supplies a signal representative of fuel quantity to a fuel indicator. The output of the other switch is supplied to another integrating current-to-voltage amplifier which in turn supplies a signal representative of the quantity of contaminants to a contaminant indicator.

대표청구항 ▼

A fluid gauging system of the kind including a capacitance sensor adapted for immersion within a fluid, a supply unit that supplies an alternating input signal to said sensor such that said sensor provides an alternating output signal that varies in accordance with change in fluid quantity, and a de

A fluid gauging system of the kind including a capacitance sensor adapted for immersion within a fluid, a supply unit that supplies an alternating input signal to said sensor such that said sensor provides an alternating output signal that varies in accordance with change in fluid quantity, and a detector circuit that receives said output signal, the improvement wherein said system includes switching control means that receives a sample of said input signal, and wherein the detector circuit includes a first switching device having first and second inputs and an output, means supplying the output signal of said sensor to the first input of said first switching device, said switching control means being coupled to the second input of said first switching device to cause switching of the said first switching device and thereby connection of the first input with said output in synchronism and in quadrature with said input signal to said sensor, such that the first switching device passes to its output only a unidirectional current component of said output signal representative of said fluid quantity, amplifier means, and means for supplying said unidirectional current component from the output of said first switching device to said amplifier means such that said amplifier means provides a d.c. signal the amplitude of which varies in accordance with said fluid quantity.