Capacitive fluid level sensor

Details Capacitive fluid level sensor Capacitive fluid level sensor

1990-07-23

1991-08-27

Shoap, Allan N.

Measuring and testing

Liquid level or depth gauge

Immersible electrode type

340620, 324663, 324678, G01F 2326

Patent

active

050422995

ABSTRACT:
A linear compensated capacitive fluid-level sensing device includes three capacitors. A measurement capacitor is positionable during use to receive a fluid. A compensation capacitor is submerged in the fluid so that the fluid fills the space between the electrodes. An offset capacitor has a capacitance equivalent to the capacitance of the measurement capacitor when only air exists between the measurement electrodes. Charge applied to each of the three capacitors is discharged to an associated differential amplifier through a respective switch when the capacitors are disconnected from a charging voltage supply. The offset amplifier generates an inverted output current that is applied to the discharge currents of the measurement and compensation amplifiers. The compensation amplifier output gates a frequency-controlled oscillator that in turn controls the switches.

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