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A fuel-gauging system has a capacitive probe comprising an outer tubular electrode and a coaxial inner electrode. The outer electrode is supplied with an alternating signal from an oscillator, the inner electrode being connected to a detector unit via a resistor. The resistor is mounted between the

A fuel-gauging system has a capacitive probe comprising an outer tubular electrode and a coaxial inner electrode. The outer electrode is supplied with an alternating signal from an oscillator, the inner electrode being connected to a detector unit via a resistor. The resistor is mounted between the electrodes about midway along the length of the probe, the resistor having a value that is selected to give a substantially linear output of the probe and is at least 0.1 of the reactance of the probe, preferably being about 0.3595 of the reactance. The resistor may be connected to a phase-sensitive circuit that is controlled by a phase-shift circuit which receives the input signals to the probe and shifts their phase by 90°, so as to produce an output that is in phase with the probe output. In this case the value of the resistor is preferably 0.2178 of the probe reactance.

대표청구항 ▼

In a capacitive fluid-gauging system of the kind having a probe that extends within a fluid container, the probe having first and second electrodes separated from one another by a gap that is filled with fluid to a height according to the height of fluid in the container; oscillator means; means con

In a capacitive fluid-gauging system of the kind having a probe that extends within a fluid container, the probe having first and second electrodes separated from one another by a gap that is filled with fluid to a height according to the height of fluid in the container; oscillator means; means connecting said oscillator means with the first electrode of said probe so as to supply an alternating input signal to said probe; detector means; and means connecting said detector means to the second electrode of said probe so as to receive an output signal from said probe, said detector means providing an output representation in response to fluid height, the improvement wherein the system includes a fixed value resistor, means connecting said resistor in series intermediate said second electrode and the said detector means, the value of the resistor being at least 0.1 of the reactance of the probe and being selected to give a substantially linear output of the probe.