Microprocessor-based liquid sensor and ice detector

• US 6,776,037 B2
• Filed: 05/01/2001
• Issued: 08/17/2004
• Est. Priority Date: 03/31/1995
• Status: Expired due to Term

• Current Assignee: Josef Maatuk
• Original Assignee: Josef Maatuk
• Inventors: Maatuk, Josef
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): Frank, Rodney T.
• Application Number:
  US09/845,979
• Publication Number:
  US 20020100318A1
• Time in Patent Office: 1,204 Days
• Field of Search: 732/95, 374/15, 374/54, 374/16, 374/45, 340/580, 340/581
• US Class Current: 73/295
• CPC Class Codes: B64D 15/20 Means for detecting icing or initiating de-icing
• CPC Class Codes: B64D 37/005 Accessories not provided for in the groups B64D37/02 - B64D37/28
• CPC Class Codes: G01F 23/22 by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water involving the use of floats G01F23/30
• CPC Class Codes: G01F 23/247 for discrete levels
• CPC Class Codes: G01F 23/248 Constructional details; Mounting of probes

Abstract

Apparatus and a method of operating any structural configuration of a heater and array of temperature sensors to measure with high accuracy, the level of stratified liquids like water and oil or water and gasoline and non-stratified liquids, liquid temperature, and other liquid properties and detect ice formation on aircraft surfaces. Thin and narrow strips of dissimilar material will be used for the heater, array of temperature sensors, mount, and coating. The connecting wires to and from the apparatus will be from the same material. Simultaneous measurements from all the temperature sensors, before and after heat is applied, will be used to generate accurate temperature profiles for the entire configuration and not just from two adjacent temperature sensors. 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.

Claims

1. An apparatus for accurately determining the level in a liquid container, or the presence of ice on a surface, said apparatus comprising:

a first layer material comprising of an alloy strip secured along the longitudinal extent of the face of an elongated substrate or plastic sheet;

a plurality of metallic pads secured to said substrate, each pad having one end electrically connected to said alloy strap to form a plurality of thermocouples, said thermocouples being spaced apart over the longitudinal extent of said alloy constantan strip;

a second layer material comprising of a thin dielectric film secured to said substrate covering said thermocouples for electrically isolating said thermocouples from air or liquid;

means for applying electrical power to said alloy strip, controlled by a power control switch, wherein both ends of said alloy strip are connected to said electrical power applying means for heating by electrical pulses of said alloy strip;

display means for indicating the liquid level in said liquid container;

a data acquisition system comprising, analog and digital circuitry, a microprocessor, and display means for indicating said liquid level from temperatures sensed by said thermocouples.

2. The apparatus recited in claim 1, whereby the alloy strip is comprised of constantan and the metallic elements are comprised of copper.

3. The apparatus recited in claim 1, wherein said constantan strip is an electrically pulsed heater and a common wire for said thermocouples.

4. The apparatus recited in claim 1 whereby said data acquisition system comprises:

first and second multiplexers for odd and even thermocouples;

wiring of said multiplexers to a single differential amplifier, an and analog to digital converter, said analog to digital filter wired to a microprocessor;

said microprocessor connected to a power supply capable of supplying power to said alloy strip, and a display capable of displaying information obtained from said microprocessor.

5. A data acquisition system as recited in claim 4, further comprising software used with the microprocessor, capable of eliminating non-random electronic hardware errors and minimizing random errors in differential voltage readings of said thermocouples.

6. A data acquisition system as recited in claim 4, further comprising of software capable of determining absolute temperature of each said thermocouples using said differential voltages.

7. A data acquisition system as recited in claim 4, further comprising of software determining the kind of liquid based on the curvature of the temperature profile, such that the transition temperature between the thermocouples in liquid and thermocouples in air Can increase or decrease depending upon the type of liquid being measured.

8. An apparatus for detecting ice on horizontal and vertical surfaces, comprising the apparatus of claim 1, further comprising a dome over one or more of the thermocouples and means for determining the response tame of the differential voltage for each thermocouple close to the response time of the voltage of the thermocouple under the dome.

9. A method for accurately detecting ice on one of horizontal and vertical and inclined surfaces, said method comprising the steps of:

operating the device of claim 8;

determining the presence of ice on any section of said surfaces by measuring a differential voltage from each said thermocouples;

determining the existence of a time-delay of said differential voltage time behavior of each thermocouple;

determining the steady-state differential voltage for each thermocouple close to the steady-state voltage of the thermocouple(s), under the dome;

determining the response time of the differential voltage for each thermocouple close to the response time of the voltage of the thermocouple(s) under the dome.

10. A method for accurately determining the liquid parameters of level, temperature and viscosity in a three-dimensional liquid container, said method comprising:

Determining the three components of the temperature profile of the liquid being measured namely;

a first temperature value indicative of the sensor exposed only to air;

a second temperature value indicative of the sensor exposed only to liquid; and

a transition range indicative of the temperature change along the length of the sensor determined by the temperature difference between the portion of the sensor in air and the portion of the sensor in liquid.