Fluid level detector

Claim 2

A liquid level indicator apparatus for a vehicle braking system having first and second containers electrically coupled to a potential reference level and having electrically conductive brake fluid therein comprising: a potential source; first and second probes each coupled to said potential source and positioned within one of said containers for developing first and second resistance values in accordance with the level of said brake fluid; voltage divider means coupling said potential source to a potential reference level; first and second switching means coupled to said first and second probes respectively and to said voltage divider means, and having an output; and current amplifier means coupled to said switching means output and coupled to a load circuit having a signal indicator and via a feedback circuit to said voltage divider means whereby a shift in fluid level causing an increased resistance value of one of said probes is accompanied by activation of said signal indicator and of said feedback circuit to effect a saturation conduction condition of said current amplifiers.

Claim 3

The liquid level indicator apparatus of claim 1 wherein each of said first and second probes is coupled by a resistor to said potential source.

Claim 4

The liquid level indicator apparatus of claim 1 wherein said voltage divider means is in the form of first and second resistors series connecting said potential source to said potential reference level with said first and second switching means coupled to the junction of said series connected resistors.

Claim 5

The liquid level indicator apparatus of claim 1 wherein each of said first and second switching means is in the form of a transistor having a base electrode coupled to one of said first and second probes, an emitter electrode coupled to said voltage divider, and a collector electrode coupled to said current amplifier means.

Claim 6

The liquid level indicator apparatus of claim 1 wherein said load circuit coupled to said current amplifier means includes a signal indicator coupled to said potential source and a zener diode coupled to said potential reference level.

Claim 7

The liquid level indicator apparatus of claim 1 wherein said feedback circuit is in the form of a resistor coupling said current amplifier means to the junction of said series connected resistors of said voltage divider means.

Claim 8

Liquid level indicator apparatus including first and second containers electrically coupled to a potential reference level and having an electrically conductive fluid therein comprising: a potential source; first and second voltage divider circuits each including a resistor connected to said potential source and to a probe positioned within one of said first and second containers for developing first and second resistance values in accordance with the level of said fluid; voltage divider means coupling said potential source to a potential reference level; current amplifier means coupling said potential source to said potential reference level, said current amplifier means having an output coupled to a load circuIt having an indicating device and by a feedback circuit to said voltage divider means; and first and second switching means coupled to said first and second voltage divider circuits respectively and to said current amplifier means and said voltage divider means whereby a shift in resistance value of one of said first and second voltage dividers, due to a shift in fluid level alters conduction of one of said switching means and said current amplifier means to activate said indicating device and feedback circuit for effecting saturation conduction of said current amplifier means.

Claim 9

Liquid level indicator apparatus including first and second containers electrically coupled to a potential reference level and having an electrically conductive fluid therein comprising: a potential source; first and second voltage divider circuits each including a resistor connected to said potential source and to a probe positioned within one of said first and second containers for developing first and second resistance values in accordance with the level of said fluid; voltage divider means coupling said potential source to a potential reference level; current amplifier means coupling said potential source to said potential reference level, said current amplifier means having an output coupled to a load circuIt having an indicating device and by a feedback circuit to said voltage divider means; and first and second switching means coupled to said first and second voltage divider circuits respectively and to said current amplifier means and said voltage divider means whereby a shift in resistance value of one of said first and second voltage dividers, due to a shift in fluid level alters conduction of one of said switching means and said current amplifier means to activate said indicating device and feedback circuit for effecting saturation conduction of said current amplifier means.

Claim 10

The liquid level indicating apparatus of claim 7 wherein said voltage divider means includes first and second resistors series coupling said potential source to a potential reference level, said resistors having a junction coupled to each of said first and second switching means and to said feedback circuit of said current amplifier means.

Claim 11

The liquid level indicating apparatus of claim 7 wherein said first and second switching means each include a transistor coupled intermediate said current amplifier means and said voltage divider means and to one of said first and second voltage divider circuits.

Claim 12

The liquid level indicating apparatus of claim 7 wherein said output of said current amplifier means is coupled via an indicating device to said potential source and via a zener diode to said potential reference level.