Apparatus for measuring level and quantity of fuel oil stored in a tank, which comprises a pair of electrodes, one being a number of segmented electrodes while the other is an elongated electrode to form a number of capacitors, a source for applying high frequency voltage to said electrodes one by one to generate electric signals, means for converting said signals to corresponding high frequency signals, means for computing height of said liquid level from frequencies of signals, and means for computing the fuel quantity. Said capacitor probe is prepared by fastening an elongated flexible substrate IS printed with said electrodes round a rigid bar S, covering the outer surface thereof with insulative material, and fitting a metallic tube. Said segmented electrodes are arranged lengthwise in two rows in zig-zagged and partly overlapped.

Liquid level and quantity measuring apparatus

A liquid level gauge for monitoring the height of liquid in a storage tank or the like. The gauge comprises an upright conducting probe adapted to be immersed in the liquid in the tank, and an upright series of electrodes closely adjacent the probe. The latter is adapted to be excited from a source of a.c. voltage generated by an astable multivibrator. Each of the electrodes is connected to the input of an amplifier through a rectifier circuit. The amplifiers are of the digital comparator type and have output terminals respectively connected by means of summing resistors to an electrical indicator such as a milliammeter, which provides an indication of the number of amplifiers being driven to full output at any particular time. The arrangement is such that each of the electrodes constitutes one plate of a capacitor, the other plate being formed by the single upright conducting probe. When a particular electrode is above the level of fluid in the tank, the magnitude of the a.c. signal received at the electrode is of a sufficiently small magnitude to provide only a low level drive voltage to its respective comparator amplifier, the latter thus assuming a low output signal level. Once a particular plate becomes submerged, the increased dielectric constant (fluid) effects an increase in the value of the capacitor, and a correspondingly larger drive signal to the amplifier results, causing the output thereof to assume a high level and yielding a contribution to the meter reading through the respective summing resistor. The meter reading thus responds to the number of electrodes submerged at any particular time, and provides an indication of the liquid level in the tank.

Liquid level gauging apparatus

A system for automatically phase aligning parallel signal processing channels such as those used in the receiving system of monopulse radars, for example. Test signals having a predetermined phase relationship are applied at the inputs of each of two signal processing channels and a phase detector measures the phase of the resulting output signals. The phase detector''s output signal is processed to control a variable phase shifter, series coupled with the local oscillator signal applied to a mixer in one of these channels, so as to cause the test signals at the output of the two processing channels to have a predetermined phase relationship.

System for phase aligning parallel signal processing channels

A liquid level sensor based on a closed field circuit comprises a ring oscillator using a symmetrical array of plate units that creates a displacement current. The displacement current varies as a function of the proximity of a liquid to the plate units. The ring oscillator circuit produces an output signal with a frequency inversely proportional to the presence of a liquid. A continuous liquid level sensing device and a two point sensing device are both proposed sensing arrangements. A second set of plates may be located inside of the probe housing relative to the sensing plate units. The second set of plates prevent any interference between the sensing plate units.

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Closed-field capacitive liquid level sensor

A single capacitor is used to measure the oil level in an engine or transmission and compensate the sensed capacitance for changes in dielectric constant. Measurements are made for two different running conditions, one giving a capacitance reading dependent only on dielectric constant and one giving a capacitance dependent on oil level as well as dielectric constant. The transmission application uses a capacitor that is fully immersed in oil when the engine is off and partly immersed when the engine is idling, so that both types of measurements can be obtained. The engine application uses a capacitor having an upper section spaced from a lower section. Only the lower section is immersed during engine idle to render dielectric constant information, while the upper section is partly immersed when the engine is off.

Jack W Schuck

Papers

Divided capacitance probe level gauge

Digital phase control circuit for synchronizing an oscillator to a harmonic of a reference frequency

Discharge circuitry for voltage doubling and switching circuitry