Liquid sensor and ice detector

Abstract

An improved apparatus and a method of measuring and interpreting reliably, simply and accurately the information on continuous liquid level, liquid temperature and other liquid properties within a vessel. The apparatus could be made of a powered heater element and temperature sensors can be screen-printed, vacuum deposited, etched, welded, soldered or plated on one or both sides of a single rigid or a flexible substrate. The geometry of the heater determines the curve shape, such as steepness or shallowness of a temperature profile along a heater. Various parallel and serial configurations of thermocouples or temperature sensors can be used to measure the temperature along a heater. Simultaneous measurements from all the temperature sensors, before and after heat is applied, are used to generate accurate temperature profiles for the entire heater. Different features of the temperature profiles will determine accurately the liquid level, liquid temperature and other liquid properties. Apparatus of the invention may also be used to detect ice formation.

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       16 . Apparatus for determining accurately liquid level in a container by providing a signal and/or signals indicative of the level to which said sensor is submerged in a liquid, said apparatus comprising: 
 a substrate having a longitudinal axis;    a common heater wire secured along the longitudinal axis of one face of said substrate;    said common heater having uniform or non-uniform cross-section provided on either side of said substrate;    a plurality of thermocouples or temperature sensors provided on one side of said substrate in longitudinally spaced relationship;    said plurality of thermocouples located at strategic vertically spaced points and located very close to the common heater on one side of said substrate;    said temperature sensors are plurality of thermocouples with hot and cold junctions connected serially or in parallel configuration;    a single cold thermocouple junction for said parallel thermocouple configuration and/or a single common hot thermocouple junction provided on one face of said substrate;    a plurality of cold thermocouple junctions for serially connected thermocouples provided on one side of said substrate in longitudinally spaced and positioned in a laterally spaced relationship to said plurality of hot thermocouples junctions;    isothermal block means for keeping said cold junction of serially connected thermocouple at the same temperature; coating of said heater, said temperature sensors and two sides of said substrate is thermally conductive, electrically insulating, chemically inert to the operating liquid, slippery and liquid impermeable;    means for applying electrical power to heat said common heater wire, controlled by a power control switch and power circuitry, wherein both ends of said common heater wire are connected to said electrical power applying means for heating by continuous or discrete electrical pulses of said common heater;    said apparatus is being adapted to be positioned within a vessel containing a volume of liquid with said coated substrate partially immersed in said liquid such that said hot and cold junctions of plurality of thermocouples will cooperate to generate a signal indicative of the continuous level of liquid within said vessel;    display means for indicating the liquid level in said liquid container;    a data acquisition means comprising a microprocessor and or a signal conditioning circuit connected to said thermocouples and display means for indicating said liquid level from one of voltage and temperature sensed by said thermocouples; and    said power and signal conditioning circuitry are provided on said substrate.    
   
   
       17 . A liquid level apparatus as set forth in  claim 16 , wherein said hot and cold plurality of thermocouple junctions generate a signal of opposite plurality.  
   
   
       18 . A liquid level apparatus as set forth in  claim 16 , wherein said apparatus thermocouples operate to generate a signal indicative of a pressure within said vessel;  
   
   
       19 . A liquid level apparatus as set forth in  claim 16 , further comprising a regulated power source for supplying power to said common heater.  
   
   
       20 . A liquid level apparatus as set forth in  claim 16 , wherein said signal from said thermocouples is supplied to signal conditioning circuitry.  
   
   
       21 . A liquid level apparatus as set forth in  claim 16 , wherein thermocouple junctions are positioned along a line extending generally parallel to the surface of said liquid.  
   
   
       22 . A method for accurately determining the density and pressure change of compressible fluid and the liquid parameters of level, absolute temperature and viscosity degradation in a three dimensional liquid container, said method comprising of three components on a monotonic profile namely: 
 a line along most of the lineal dimension of the sensor that is immersed in liquid;    a line along a significant portion of the lineal dimension of the sensor that is in air or other medium above the liquid;    a steep or shallow curved line connecting said two lines;    reading of a point or a few points along each of said three components will be used to construct said profile;    adding, averaging or interpolation of said readings from said points determine with different accuracy the said density and pressure changes, liquid level, absolute temperature and viscosity degradation.    
   
   
       23 . The method recited in  claim 17 , wherein said monotonic profile is a voltage or temperature profile, each of its three components is constructed from reading of one or more hot thermocouple junctions after power is applied to the heater and after zeroing one of the voltage and the temperature reading from all of the hot thermocouple junctions while the cold junctions temperature remains equal and constant for all of the cold thermocouple junctions.  
   
   
       24 . The apparatus recited in  claim 16 , wherein said common heater is an electrically pulsed heater and a common wire for the hot and cold junction of parallel configuration of thermocouples.  
   
   
       25 . The method recited in  claim 17 , wherein the determining step includes detecting the presence of two or more different stratified liquids, such as oil and water, and determining the level of each liquid.  
   
   
       26 . The method recited in  claim 17 , wherein the determining step includes detecting the level at pre-set points at one of the bottom and top of liquid containers such as oil pans, fuel tanks and coolant reservoir.  
   
   
       27 . A data acquisition system comprising: 
 an analog power circuitry connected to the heater and an analog signal conditioning circuitry with self-calibrated differential amplifier is connected to all possible configuration of thermocouples;    a first and second multiplexers for odd and even thermocouples connected to said configuration with parallel thermocouples; wiring of said multiplexers to an analog signal conditioning circuitry and a single differential amplifier and analog to digital converter; said analog to digital filter wired to a microprocessor;    said microprocessor wired to the apparatus recited in  claim 1 , and a display through a serial port and digital to analog input/output; said microprocessor connected to a health monitoring electronic circuitry for the apparatus in  claim 1;     said microprocessor connected to a power supply circuitry capable of having a power switched on and off; and    said microprocessor comprise of algorithms for signal conditioning and signal processing.    
   
   
       28 . A data acquisition system as recited in  claim 27 , further comprising software used with the microprocessor of said data acquisition system, capable of eliminating non-random electronic hardware errors and minimizing random errors in differential voltage reading of said thermocouples.  
   
   
       29 . A data acquisition system as recited in  claim 27 , further comprising of software capable of determining absolute temperature of each said thermocouples using said differential voltages.  
   
   
       30 . A data acquisition system as recited in  claim 27 , further comprising of software determining the kind of liquid based on curvature of the temperature profile and the rise of temperature of the thermocouples in liquid, and thermocouples in air.