# US 8,739,620 B1 · Liquid-sensing probe and methods for using the same

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- Number: US 8,739,620 B1
- Document ID: US8739620B1
- Status: Granted
- Kind: B1
- Application number: 12/860,394
- Filed: 2010-08-20
- Granted: 2014-06-03
- Earliest claimed: 2009-08-20
- Assignees: Sierra Lobo, Inc.
- Applicants: Mark S. Haberbusch; Jacob C. Ickes; Adam Thurn; Branden J. Lawless
- Inventors: Mark S. Haberbusch; Jacob C. Ickes; Adam Thurn; Branden J. Lawless
- Web page: https://patentgrep.com/patent/US8739620B1

## CPC

- G01F 23/00: Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME

## Abstract

A sensor assembly includes a main body, a sensor, and a filler. The main body includes an outer surface having a continuously-variable radius of curvature in at least one portion. A sensor in thermal communication with a region of that surface having relatively low radius of curvature is disposed in the assembly recessed from the outer surface. Liquid droplets adhered to the outer surface in this region tend to migrate to a distant location having a higher radius of curvature. The main body has low thermal conductivity. The filler has a relatively higher thermal conductivity and, in embodiments, fills an opening in the outer surface of the main body, providing a thermally-conductive pathway between the sensor and the surrounding environment via the opening. A probe having a plurality of such sensors, and methods of detecting the presence of liquid and phase transitions in a predetermined space are also disclosed.

## Claims

### Claim 1

A sensor assembly comprising:
a main body comprising an outer surface, at least a portion of which is curved such that its radius of curvature increases continuously from a first location on said outer surface to a second location on said outer surface;
a sensor recessed in said main body beneath said outer surface; and
a conductive pathway between said sensor and an environment outside said main body adjacent said first location, said conductive pathway having a thermal conductivity greater than the thermal conductivity of said main body.

### Claim 2 (depends on 1)

The sensor assembly of claim 1, said conductive pathway having a thermal conductivity at least one order of magnitude greater than the thermal conductivity of said main body.

### Claim 3 (depends on 1)

The sensor assembly of claim 1, said main body having a thermal conductivity not more than 2 W/m-K, said conductive pathway having a thermal conductivity of at least 14 W/m-K.

### Claim 4 (depends on 1)

The sensor assembly of claim 1, said main body having a thermal conductivity not more than 1 W/m-K, said conductive pathway having a thermal conductivity of at least 18 W/m-K.

### Claim 5 (depends on 1)

The sensor assembly of claim 1, said outer surface being conical such that its radius of curvature in a direction normal to an axis of symmetry of said conical surface increases continuously in a longitudinal direction from a first end thereof to a second end thereof.

### Claim 6 (depends on 5)

The sensor assembly of claim 5, further comprising an opening in said outer surface at said first location adjacent said first end, and a conductive filler in thermal contact with said sensor, said conductive filler providing said conductive pathway via said opening.

### Claim 7 (depends on 6)

The sensor assembly of claim 6, said conductive filler filling said opening such that an exposed portion of said filler has a continuous contour with, and matches the curvature of, said outer surface.

### Claim 8 (depends on 7)

The sensor assembly of claim 7, said exposed portion of said filler being substantially seamless with said outer surface adjacent said opening.

### Claim 9 (depends on 5)

The sensor assembly of claim 5, said conductive pathway having a thermal conductivity at least one order of magnitude greater than the thermal conductivity of said main body.

### Claim 10 (depends on 5)

The sensor assembly of claim 5, said main body having a thermal conductivity not more than 2 W/m-K, said conductive pathway having a thermal conductivity of at least 14 W/m-K.

### Claim 11 (depends on 5)

The sensor assembly of claim 5, said conical outer surface having a cone angle not more than 20°.

### Claim 12 (depends on 1)

The sensor assembly of claim 1, said main body comprising polyamide-imide polymer having a thermal conductivity of about 0.5 W/m-K.

### Claim 13 (depends on 1)

The sensor assembly of claim 1, said outer surface being entirely curved.

### Claim 14 (depends on 1)

The sensor assembly of claim 1, said sensor comprising a diode.

### Claim 15 (depends on 1)

A probe comprising a support strip having at least one conductor extending therein along the probe's length, and a sensor assembly as in claim 1, the sensor in said sensor assembly being in electrical communication with said at least one conductor for conducting signals to and/or from said sensor.

### Claim 16 (depends on 15)

The probe of claim 15:
the main body of said sensor assembly further comprising a flange at an end thereof, and
said support strip comprising a first cover layer, a second cover layer and a circuit layer sandwiched therebetween, said circuit layer comprising said conductor, said first cover layer having an aperture through which the main body of said sensor assembly extends and which is sized to prevent the flange from passing therethrough, said flange being sandwiched between said circuit layer and said first cover layer adjacent said aperture.

### Claim 17 (depends on 16)

The probe of claim 16, comprising a plurality of said sensor assemblies disposed along the length of said support strip, having respective main bodies extending through respective apertures in said first cover layer, their respective flanges being sandwiched between said circuit layer and said first cover layer, said circuit layer comprising a plurality of conductors extending along the strip's length and in electrical communication with respective sensors in said plurality of sensor assemblies.

### Claim 18 (depends on 16)

The probe of claim 16, said conductive pathway having a thermal conductivity at least one order of magnitude greater than the thermal conductivity of said main body.

### Claim 19 (depends on 16)

The probe of claim 16, the outer surface of said main body being conical such that its radius of curvature in a direction normal to an axis of symmetry of said conical surface increases continuously in a longitudinal direction from a first end thereof to a second end thereof.

### Claim 20 (depends on 19)

The probe of claim 19, said flange being located at said second end.

### Claim 21 (depends on 19)

The probe of claim 19, further comprising an opening in said outer surface adjacent said first end, and a conductive filler in thermal contact with said sensor, said conductive filler providing said conductive pathway via said opening.

### Claim 22 (depends on 21)

The probe of claim 21, said conductive filler filling said opening such that an exposed portion of said filler has a continuous contour with, and matches the curvature of, said outer surface.

### Claim 23 (depends on 1)

A method of detecting whether liquid is present in a predetermined space, comprising the steps of:
exposing the main body of the sensor assembly of claim 1 to said predetermined space;
applying a current to the sensor in said sensor assembly to generate heat at the sensor, wherein heat generated at said sensor is dissipated via the conductive pathway in said sensor assembly to the predetermined space; and
detecting the voltage drop across said sensor as a function of time and correlating voltage drop-versus-time data for said sensor with the rate of dissipation of said heat to determine the presence or absence of liquid in the predetermined space.

### Claim 24 (depends on 23)

The method of claim 23, said predetermined space being in a reduced-gravity environment.

### Claim 25 (depends on 23)

The method of claim 23, said predetermined space being a location inside a storage vessel in a reduced-gravity environment, wherein the liquid whose presence or absence is detected is a cryogenic liquid within said storage vessel.

### Claim 26 (depends on 23)

The method of claim 23, further comprising determining a transition from liquid-to-vapor or vapor-to-liquid by calculating a first derivative of the voltage drop across said sensor as a function of time, and correlating a peak in said first derivative with said transition.

### Claim 27 (depends on 26)

The method of claim 26, further comprising operating a computer according to an algorithm so that said computer carries out said first-derivative calculation based on voltage-versus-time data from said sensor, and records vapor-to-liquid or liquid-to-vapor transitions based on correlated peaks in said first derivative, said computer storing information related to said transitions in a memory and/or outputting said information to a medium.