Analog liquid level sensor

A sensor for determining the analog location of the surface of liquid in a container, comprising:

• an elongated probe inserted into said container, said probe having one portion arranged above the surface of said liquid and having another portion submerged in said liquid;
• a first temperature sensor operatively arranged within said probe adjacent the upper end thereof to sense the temperature above said liquid surface;
• a second temperature sensor operatively arranged within said probe adjacent the lower end thereof to sense the temperature of said liquid at a point beneath said surface;
• a resistance wire operatively arranged within said probe;
• a current source operatively arranged to supply a current to said wire;
• and
• a voltmeter arranged to measure the voltage drop across said wire;
• wherein the resistance of said wire may be calculated according to the equation:
• RT=ƒ[kaTaHh+kwTwH(1−h)]={fraction (V/i)}
• where RT is the resistance of said wire, ƒ is the symbol for “a function of”, ka is a constant for the probe first portion, Ta is the temperature sensed by the first temperature sensor, kw is a constant for the probe second portion, Tw is the temperature sensed by said second temperature sensor, H is the vertical distance between said first and second temperature sensors, h is the distance from said first temperature sensor to said liquid surface, and V is the voltage sensed by said voltmeter, and i is the current in said wire;
• such that the liquid level may be indicated by the value of h when the liquid level is between said first and second sensors, but will be indicated by a first constant value if the second temperature sensor is above said liquid surface and will be indicated by a second constant value if the first temperature sensor is arranged beneath said liquid surface.