Continuous sensor measurement in harsh environments

Patent metadata

Field	Value
Publication number	US-2016266277-A1
Application number	US-201415034478-A
Country	US
Kind code	A1
Filing date	Nov 5, 2014
Priority date	Nov 6, 2013
Publication date	Sep 15, 2016
Grant date	—

Abstract

A sensor module may be formed including a core of ferromagnetic material associated with a wire coil forming a passive inductor resonant circuit, which may be used in temperature sensor modules and pressure sensor modules suitable for use in high temperature, high pressure, and corrosive environments. The passive inductor resonant circuits of the sensors may be tuned such that its resonant frequency is in a bounded frequency band interrogable with an electromagnetic energy signal having a frequency of less than or equal to about 10 MHz. Such sensors may be disposed in series in a sensor array, interrogable with an interrogation module, where the interrogation module may demultiplex, the frequencies of the multiple sensors to determine the environmental conditions sensed by the individual sensors.

First claim

What is claimed:

1 . A sensor module, comprising: a core of ferromagnetic material associated with a wire coil forming a passive inductor resonant circuit, wherein the passive inductor resonant circuit is tuned such that its resonant frequency is in a bounded frequency band interrogable with an electromagnetic energy signal having a frequency of less than or equal to about 10 MHz.

2 . A temperature sensor module, comprising:
a housing; a temperature sensor disposed within the housing and comprising a core of ferromagnetic material associated with a wire coil forming a passive inductor resonant circuit, an inductance of which varies with temperature; and wherein the passive inductor resonant circuit is tuned such that its resonant frequency is in a bounded frequency band interrogable with an electromagnetic energy signal having a frequency of less than or equal to about 10 MHz.

3 . The temperature sensor module of claim 2 , wherein the inductance (L) of the passive inductor resonant circuit follows the equation:

L
=

N
2



μ
r



μ
o


A

l
m

where
N=number of turns of the coil of wire,
A=cross sectional area of the ferromagnetic core material,
l m =mean magnetic path length through the core,
μ r =relative permeability of the ferromagnetic core material, and
μ o permeability of free space;

wherein each of A, l m , and μ r vary as a function of temperature.

4 . The temperature sensor module of claim 2 , wherein the core of ferromagnetic material comprises a ferromagnetic material having a closed-core geometry with a gap perpendicular to the magnetic flux path, and the wire coil is disposed around at least a portion of the core.

5 . The temperature sensor module of claim 4 , wherein the inductance (L) of the passive inductor resonant circuit follows the equation:

L
=

N
2


A

l
m

μ

r



1



μ
o

+

l
g

μ

r



2



μ
o

where
N=number of turns of the coil of wire,
A=cross sectional area of the ferromagnetic core material,
l m =mean magnetic path length through the core,
μ r1 =relative permeability of the ferromagnetic core material,
μ o =permeability of free space,
l g =length of the gap, and
μ r2 =relative permeability of material in the gap;

wherein each of A, l m , l g , and μ r1 vary as a function of temperature.

6 . The temperature sensor module of claim 5 , wherein the inductance of the passive inductor resonant circuit is primarily a function of a length of the gap.

7 . The temperature sensor module of claim 5 , wherein a ratio of μ r2 to μ r1 is at least 50:1.

8 . The temperature sensor module of claim 2 , wherein the temperature sensor is configured to measure a temperature range, the range having a maximum temperature below a Curie temperature of the core and the range inclusive of a temperature of at least 220° C.

9 . A pressure sensor module, comprising:
a core, including a fixed core portion and a deflectable core portion, comprising a ferromagnetic material associated with a wire coil forming a passive inductor resonant circuit; a gap between at least a portion of the fixed core portion and an internal surface of the deflectable core portion; wherein a pressure applied to an outer surface of the deflectable core portion deflects the deflectable core portion, decreasing a length of the gap and affecting an inductance of the resonant circuit.

10 . The pressure sensor module of claim 9 , wherein the passive inductor resonant circuit is timed such that its resonant frequency is in a bounded frequency hand interrogable with an electromagnetic energy signal having a frequency of less than or equal to about 10 MHz.

11 . The pressure sensor module of claim 9 , wherein the inductance (L) of the passive inductor resonant circuit follows the equation:

L
=

N
2


A

l
m

μ

r



1



μ
o

+

l
g

μ

r



2



μ
o

where
N=number of turns of the coil of wire,
A=cross sectional

Assignees

• Fmc Tech Inc

Inventors

• Blackburn T Joel
• Knaub Mitchell K
• Triche Matthew S
• Sanford L Lane
• Snell Eric J
• Lisk Mahlon
• Honeker Levi

Classifications

• G01K7/36

  using magnetic elements, e.g. magnets, coils (magnetic elements per se H01F) · CPC title

• G01V9/005

  by thermal methods, e.g. after generation of heat by chemical reactions · CPC title

• G01V11/002 Primary

  Details, e.g. power supply systems for logging instruments, transmitting or recording data, specially adapted for well logging, also if the prospecting method is irrelevant (means for transmitting well survey signals E21B47/12; signal transmission systems in general G08C; transmission in general H04B) · CPC title

• G01L9/007 Primary

  using variations in inductance · CPC title

• G01K1/026

  arrangements for monitoring a plurality of temperatures, e.g. by multiplexing · CPC title