Liquid condition and level detector

Claim 1

ELECTRICAL MEASURING APPARATUS COMPRISING, IN COMBINATION, SENSING MEANS ADAPTED TO BE POSITIONED WITHIN A FLUID, THE PRESENCE OF WHICH IS TO BE DETERMINED; AMPLIFYING MEANS INCLUDING INPUT AND OUTPUT TERMINALS; A FIRST FEEDBACK PATH INCLUDING SAID SENSING MEANS; A SECOND FEEDBACK PATH; SAID FIRST AND SECOND FEEDBACK PATHS CIRCUIT CONNECTED INTERMEDIATE SAID AMPLIFIER OUTPUT AND INPUT TERMINALS TO COMBINEDLY PRESENT OPPOSITELY PHASED FEEDBACK SIGNALS TO SAID AMPLFIIER INPUT TERMINALS; SAID FEEDBACK SIGNALS PRESENTED BY SAID FIRST AND SECOND FEEDBACK PATHS CANCELLING TO PRESENT A SUBSTANTIALLY ZERO NET FEEDBACK SIGNAL CORRESPONDING TO A FIRST PREDETERMINED CONDITION OF FLUID PRESENCE AT SAID SENSING MEANS, WHEREBY SAID AMPLYFING MEANS WILL BE IN A NON-OSCILLATING CONDITION; VARIATION OF SAID CONDITION OF FLUID PRESENCE TO A SECOND PREDETERMINED CONDITION EFFECTING THE ELECTRICAL CHARACTERISTICS OF SAID SENSING MEANS TO PRESENT A NET POSITIVE FEEDBACK SIGNAL TO SAID AMPLFIIER INPUT TERMINALS, WHEREBY SAID AMPLIFYING MEANS WILL BE IN AN OSCILLATING CONDITION; SAID SECOND PREDETERMINED CONDITION LYING WITHIN A PREDETERMINED RANGE OF FLUID CONDITIONS; SAID AMPLIFIER MEANS WHEN IN SAID OSCILLATING CONDITION BEING NEAR ITS SATURATION LEVEL, THEREBY PROVIDING A SUBSTANTIALLY CONSTANT AMPLITUDE SOURCE OF OSCILLATION RESPONSIVE TO ANY OF A PLURALITY OF FLUID CONDITIONS WITHIN SAID PREDETERMINED RANGE; SAID AMPLIFIER MEANS MAINTAINING SAID SUBSTANTIALLY CONSTANT AMPLITUDE SOURCE OF OSCILLATION RESPONSIVE TO VARIATIONS OF SAID SECOND CONDITION OF FLUID PRESENCE LYING WITHIN SAID PREDETERMINED RANGE; FLUID CONDITION SENSING MEANS FOR DETERMINED THE PARTICULAR FLUID CONDIU TION WITHIN SAID PREDETERMINED RANGE; SAID FLUID CONDITION SENSING MEANS OPERATING IN CONJUNCTION WITH SAID OSCILLATING AMPLIFIER MEANS, WHEREBY SAID OSCILLATING AMPLIFIER MEANS PROVIDES A SUBSTANTIALLY CONSTANT AMPLITUDE FIRST SIGNAL FOR INDICATING THE PRESENCE OF A FLUID CONDITION WITH IN SAID PREDETERMINED RANGE AND SAID FLUID SENSING MEANS PROVIDES A SECOND SIGNAL FOR INDICATING THE PARTICULAR FLUID CONDITION WITHIN SAID PREDETERMINED RANGE.