Capacitive fuel composition sensor with slow oscillator and high speed switch

Patent · Tue Jul 27 04:00:00 EDT 1993

OSTI ID:6329887

Kapsovathis, N S; Wright, C D; Sanders, S P; Johnson, N M; Chun, F C

A fuel composition sensor is described for a fuel mixture in a fuel supply line for a combustion engine wherein the fuel mixture comprises two fuels of different dielectric constants in unknown relative concentrations, at least one of the fuels being electrically conductive, the sensor comprising, in combination: a sensor capacitor in the fuel line adapted for fuel flow therethrough so that the fuel mixture provided to the engine comprises a dielectric which determines the capacitance thereof but also comprises a capacitor shorting electrical conductance; a reference capacitor of constant capacitance in series with the sensor capacitor to form therewith a voltage divider having an output junction; and circuit means comprising a square wave oscillator with an output high speed switching MOSFET connected in series with a resistance across an electric power supply, the reference and coupling capacitors being connected in series across the MOSFET with the coupling capacitor having an electrode connected to the junction of the resistance and MOSFET, the circuit means being effective to repetitively produce, at a comparatively low frequency, a predetermined fast voltage change across the series combination of the reference and sensor capacitors to produce a corresponding voltage change at the output junction comprising an initial voltage change essentially proportional to the capacitance ratio of the sensor and reference capacitors followed by an opposite voltage change due to leakage current through the fuel mixture, whereby the initial voltage change indicates the fuel composition.

• Assignee: General Motors Corp., Detroit, MI (United States); National Semiconductor Corp., Santa Clara, CA (United States)
• Patent Number(s): A; US 5231358
• Application Number: PPN: US 7-809618
• OSTI ID: 6329887
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
330100* -- Internal Combustion Engines
CHEMICAL COMPOSITION
CONTROL
CONTROL EQUIPMENT
DESIGN
DIELECTRIC PROPERTIES
DISPERSIONS
DUAL-FUEL ENGINES
ELECTRIC POTENTIAL
ELECTRICAL PROPERTIES
ENERGY SUPPLIES
ENGINES
EQUIPMENT
FIELD EFFECT TRANSISTORS
FUEL SUPPLIES
FUELS
HEAT ENGINES
INTERNAL COMBUSTION ENGINES
LIQUID FUELS
MIXING
MIXTURES
MOS TRANSISTORS
MOSFET
OPERATION
PHYSICAL PROPERTIES
PROBES
SEMICONDUCTOR DEVICES
TRANSISTORS