U.S. patent application number 11/527046 was filed with the patent office on 2007-01-25 for temperature sensor apparatus and method.
This patent application is currently assigned to Delphi Technologies, Inc.. Invention is credited to Charles R. Harrington, Michel F. Sultan, Da Yu Wang.
Application Number | 20070019704 11/527046 |
Document ID | / |
Family ID | 34062926 |
Filed Date | 2007-01-25 |
United States Patent
Application |
20070019704 |
Kind Code |
A1 |
Sultan; Michel F. ; et
al. |
January 25, 2007 |
Temperature sensor apparatus and method
Abstract
A system and method for determining a temperature including: a
temperature sensor including: a substrate resistance configured to
be primarily responsive to a temperature of a substrate; and a
membrane resistance configured to be primarily responsive to a
temperature of a membrane. The substrate resistance and the
membrane resistance are arranged in a series circuit configured to
facilitate measurement of a voltage responsive to a temperature
change. The system also includes a controller in operable
communication with the temperature sensor. The method includes:
receiving a temperature signal, the temperature signal indicative
of a composite temperature variation including a first varying
portion and a second varying portion; configuring the temperature
signal to eliminate the second varying portion; and generating a
temperature value based on the configuring wherein the temperature
value is substantially based on the first varying portion.
Inventors: |
Sultan; Michel F.; (Troy,
MI) ; Harrington; Charles R.; (Troy, MI) ;
Wang; Da Yu; (Troy, MI) |
Correspondence
Address: |
DELPHI TECHNOLOGIES, INC.
M/C 480-410-202
PO BOX 5052
TROY
MI
48007
US
|
Assignee: |
Delphi Technologies, Inc.
|
Family ID: |
34062926 |
Appl. No.: |
11/527046 |
Filed: |
September 25, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10621140 |
Jul 16, 2003 |
7131766 |
|
|
11527046 |
Sep 25, 2006 |
|
|
|
Current U.S.
Class: |
374/141 ;
374/E7.042 |
Current CPC
Class: |
G01K 7/42 20130101 |
Class at
Publication: |
374/141 |
International
Class: |
G01K 1/14 20060101
G01K001/14 |
Claims
1-24. (canceled)
25. A method of determining a temperature comprising: receiving a
temperature signal, said temperature signal indicative of a
composite temperature variation including a first varying portion
and a second varying portion; configuring said temperature signal
to eliminate said second varying portion; and generating a
temperature value based on said configuring wherein said
temperature value is substantially based on said first varying
portion.
26. The method of claim 25 wherein said temperature signal
comprises a differential voltage.
27. The method of claim 25 wherein said configuring includes
scaling said temperature signal and combining said scaled
temperature signal with an additional signal to cancel said second
varying portion.
28. The method of claim 25 wherein said scaling includes a gain
based on a thermal coupling and indicative of a relative proportion
of said first varying portion and said second varying portion.
29. The method of claim 25 wherein said temperature signal
comprises a voltage from a bridge, said bridge formed with two
pairs of resistances, a first pair corresponding to a substrate
resistance, and a second pair corresponding to a membrane
resistance.
30. The method of claim 25 wherein said first varying portion
corresponds to variations of about 1 to 100 milliseconds and said
second varying portion corresponds to variations in excess of about
200 milliseconds.
31. A system for determining a temperature comprising: a means for
receiving a temperature signal, said temperature signal indicative
of a composite temperature variation including a first varying
portion and a second varying portion; a means for configuring said
temperature signal to eliminate said second varying portion; and a
means for generating a temperature value based on said configuring
wherein said temperature value is substantially based on said first
varying portion.
Description
BACKGROUND
[0001] This invention relates to a temperature sensor bridge
apparatus and an algorithm for processing signals therefrom.
Temperature sensors with fast response-time are desirable for a
number of applications. A conventional approach for fast
temperature sensing a micromachined MEMS device with a low thermal
mass membrane where the temperature detector is located. The
detector typically responds very quickly during the initial phase
of a thermal event, followed by a much slower phase that is
representative of the slower dynamics of the bulk of the silicon
device. Unfortunately, the slower response due to the bulk of the
silicon impedes detection of the faster dynamics.
[0002] Therefore, it would be beneficial to provide an approach
whereby the fast response component is detected and extracted
through a novel use of a temperature detector bridge and associated
electronics.
BRIEF SUMMARY
[0003] Disclosed herein is a temperature sensor comprising: a first
substrate resistance configured to be primarily responsive to a
temperature of a substrate; a first membrane resistance configured
to be primarily responsive to a temperature of a membrane; and
wherein the first substrate resistance and the first membrane
resistance are arranged in a series circuit configured to
facilitate measurement of a voltage across each responsive to a
temperature change.
[0004] Also disclosed herein is a system for determining a
temperature comprising: a temperature sensor comprising: a first
substrate resistance configured to be primarily responsive to a
temperature of a substrate; and a first membrane resistance
configured to be primarily responsive to a temperature of a
membrane. The first substrate resistance and the first membrane
resistance are arranged in a series circuit configured to
facilitate measurement of a voltage across each responsive to a
temperature change. The system also includes a controller in
operable communication with the temperature sensor, the controller
configured to receive and condition a signal indicative of a
temperature.
[0005] Further disclosed herein is a method of determining a
temperature comprising: receiving a temperature signal, the
temperature signal indicative of a composite temperature variation
including a first varying portion and a second varying portion;
configuring the temperature signal to eliminate the second varying
portion; and generating a temperature value based on the
configuring wherein the temperature value is substantially based on
the first varying portion.
[0006] Also disclosed herein, in yet another embodiment, is a
system for determining a temperature. The system comprising: a
means for receiving a temperature signal, the temperature signal
indicative of a composite temperature variation including a fast
varying portion and a slowly varying portion; a means for
configuring the temperature signal to eliminate the slowly varying
portion; and a means for generating a temperature value based on
the configuring wherein the temperature value is substantially
based on the fast varying portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The present invention will now be described, by way of an
example, with references to the accompanying drawings, wherein like
elements are numbered alike in the several figures in which:
[0008] FIG. 1 depicts a simplified block diagram for employing an
implementation of an exemplary embodiment;
[0009] FIG. 2A is a diagram depicting an implementation of a
temperature sensor;
[0010] FIG. 2B is a selected cross sectional view of the sensor of
FIG. 2A depicting an implementation of a temperature sensor;
[0011] FIG. 3A is a diagram depicting an implementation of a
temperature sensor in accordance with an exemplary embodiment;
[0012] FIG. 3B is a selected cross sectional view of the sensor of
FIG. 3A depicting an implementation of a temperature sensor in
accordance with an exemplary embodiment;
[0013] FIG. 4 is a simplified schematic diagram depicting a bridge
amplifier network utilizing an exemplary temperature sensor in
accordance with an exemplary embodiment;
[0014] FIG. 5 is simplified schematic diagram depicting a bridge
amplifier network utilizing an exemplary temperature sensor in
accordance with an exemplary embodiment; and
[0015] FIG. 6 is a block diagram depicting a flow chart of
methodology in accordance with an exemplary embodiment.
DESCRIPTION OF AN EXEMPLARY EMBODIMENT
[0016] Temperature sensors with fast response-time are desirable
for a number of applications including, but not limited to
automotive engine control and emission control. A conventional
approach for fast temperature sensing includes a
micro-electro-mechanical systems (MEMS) device. A low thermal mass
membrane includes the temperature detector. The detector typically
responds very quickly during the initial phase of a thermal event,
followed by a much slower phase that is representative of the
slower dynamics associated with the bulk of the silicon device.
Disclosed herein in an exemplary embodiment is an apparatus and
methodology whereby the fast response component is extracted
utilizing a temperature detector bridge and associated
electronics.
[0017] Referring to FIG. 1, reference numeral 10 generally
designates a control system suitable for implementation of the
disclosed embodiments. It should be noted that although the
disclosed embodiments may be described by way of reference to
temperature sensors for engine and emission control applications,
it will be appreciated that such references are illustrative only
and the disclosed embodiments may be applied to any instance where
temperature sensing is desired
[0018] The temperature sensor 20 transmits temperature signal(s) 22
to controller 16 for processing in accordance with an exemplary
embodiment. Controller 16 executes a processing algorithm
performing a methodology 100 (See FIG. 5) for processing the
temperature signal(s) 22. Preferably, the sensing electronics
associated with the temperature sensor 20 are configured integral
with the temperature sensor 20 or controller 16. Advantageously,
this approach further reduces cost and simplifies the interface
electronics. Further details of the algorithm 100 may be found at a
later point herein.
[0019] The temperature signal 22, among others, is applied to the
controller 16. The controller 16 processes all input signals to
generate values corresponding to each of the signals resulting in a
temperature value being made available for processing in various
algorithms as prescribed herein. Measurement signals, such as the
abovementioned are also commonly linearized, compensated, and
filtered as desired or necessary to enhance the characteristics or
eliminate undesirable characteristics of the acquired signal. For
example, the signals may be linearized to improve processing speed,
or to address a large dynamic range of the signal. In addition,
frequency or time based compensation and filtering may be employed
to eliminate noise or avoid undesirable spectral
characteristics.
[0020] In order to perform the prescribed functions and desired
processing, as well as the computations therefore (e.g., the
temperature sensor signal processing, control algorithm(s), and the
like), controller 16 may include, but not be limited to, a
processor(s), computer(s), DSP(s), memory, storage, register(s),
timing, interrupt(s), communication interface(s), and input/output
signal(s) interfaces, and the like, as well as combinations
comprising at least one of the foregoing. Moreover, controller 16
may include or be implemented with various processors, controllers,
microcontrollers, logic/gate arrays, programmable logic arrays
(PLA), programmable logic devices, and the like, as well as
combinations including any of the foregoing. For example,
controller 16 may include input signal processing and filtering to
enable accurate sampling and conversion or acquisitions of such
signals from communications interfaces. Additional features of
controller 16 and certain processes therein are thoroughly
discussed at a later point herein.
[0021] As exemplified herein and disclosed above one such process
may be determining a temperature value from temperature signal(s)
22. Controller 16 receives various input signals including, but not
limited to, those identified above, to facilitate such processing
and may provide one or more output signals in response. Also
received by the controller 16 are a variety of implementation
specific parameters, signals and values for initialization and
characterization of the prescribed processes and to identify
various states of the processes herein.
[0022] Continuing now with FIGS. 2A and 2B as well, a simple MEMS
temperature sensor is shown generally employing a membrane with a
resistance exhibiting a high thermal coefficient on a silicon
substrate. Two lead traces with low resistance for interconnection
are also depicted. Turning now to FIGS. 3A and 3B, a MEMS
temperature sensor 20 in accordance with an exemplary embodiment is
depicted. A membrane with a resistance 24, also exhibiting a high
thermal coefficient denoted R.sub.m, is depicted. In addition,
another resistance 26 also denoted R.sub.s, in this instance
mounted primarily on a silicon substrate 28 is depicted. A
plurality of traces 30, which facilitate interconnection are also
depicted. It will be appreciated that in an exemplary embodiment
two membrane resistances, R.sub.m 24 and two substrate resistances,
R.sub.s 26, are employed to facilitate implementation with a
Wheatstone bridge circuit. It will be appreciated that the
exemplary embodiments as disclosed herein are equally applicable
employing a plurality of resistances as the membrane resistances,
R.sub.m 24 and substrate resistances, R.sub.s 26, or even a single
membrane resistance, R.sub.m 24 and a single substrate resistance
R.sub.s 26. Implementations with other resistance configurations
would, of course, require varied electrical circuit interfaces.
[0023] A basic understanding of the mathematical background will be
beneficial for appreciation of the exemplary embodiments as
disclosed herein. Let R.sub.m and R.sub.s be the resistances of two
thin film temperature detectors, the first one on a thin, low
thermal mass membrane 24, and the second one on a high thermal mass
silicon substrate 26. Preferably, but not necessarily, these
resistors are made of the same material that exhibits a high
temperature coefficient of resistance. In an exemplary embodiment,
a temperature coefficient of resistance in excess of 3000 parts per
million (ppm) was employed. However, a temperature coefficient of
resistance in excess in excess of about 1200-1500 parts per million
(ppm) is satisfactory.
[0024] Let the two resistances be equal when stabilized at an
ambient temperature T.sub..alpha.:
R.sub.m(T.sub..alpha.)=R.sub.s(T.sub..alpha.)=R.sub..alpha. (1)
When subjected to a temperature step .DELTA.T, the two resistances
R.sub.m and R.sub.s increase with different dynamic responses, with
the resistance of the detector on the membrane R.sub.m reaching its
final value at a faster rate than the detector on bulk silicon
R.sub.s. The final values at temperature T=T.sub..alpha.+.DELTA.T
are: R.sub.m(T)=R.sub.s(T)=R.sub..alpha.+.DELTA.R (2) where
.DELTA.R=R.alpha.(1+c.DELTA.T) (3) where "c" is the temperature
coefficient of resistance for the material.
[0025] Let the response-time of the temperature detector on a
"free-standing", thermally isolated membrane, R.sub.m 24 be
.tau..sub.f, and the response-time of the temperature detector on a
bulk silicon device R.sub.s 26 be .tau..sub.s. Both time constants
.tau..sub.f and .tau..sub.s depend significantly on the geometrical
design as well as the material thermal properties of the membrane
and the bulk silicon device. For a practical configuration though,
it will be appreciated that the membrane cannot be entirely
freestanding. Often, it is part of a silicon device as illustrated
in FIG. 2, with physical and thermal anchoring to the surrounding
bulk silicon 28. Although FIG. 3A shows a silicon substrate 28,
other substrate materials may be suitable as well, including, but
not limited to, ceramic or silicon carbide substrates.
[0026] For such a configuration, as the response of the detector is
primarily a fast rising/varying portion representative of the
membrane dynamics denoted as .tau..sub.f, followed by a slowly
varying response that is representative of the bulk silicon
substrate dynamics .tau..sub.s. It will be appreciated then, that a
composite response-time depends primarily on the degree of thermal
coupling between the membrane and the bulk silicon substrate. In an
exemplary embodiment, a first varying response corresponding to the
fast varying response may be on the order of milliseconds or tens
of milliseconds, while a second varying response corresponding to
the slowly varying response may be on the order of hundreds of
milliseconds or seconds. Therefore, for a first approximation, the
response-times of a detector on a practical membrane detector,
R.sub.m 24 and a sensor on bulk silicon R.sub.s 26 are given by:
R.sub.m(t)=R.sub..alpha.+.DELTA.R
{(1-.alpha.)[1-exp(-t/.tau..sub.f)]+.alpha.[1-exp(-t/.tau..sub.s)]}
(4) R.sub.s(t)=R.sub..alpha.+.DELTA.R [1-exp(-t/.tau..sub.s)] (5)
where ".alpha." is a coefficient that depends on the degree of
thermal coupling between the membrane and the surrounding bulk
silicon substrate. For a membrane with a very high level of thermal
coupling, .alpha..about.1, and for a membrane with very good
thermal isolation, .alpha..about.0. Therefore, for a practical
situation in an actual physical implementation, .alpha. is between
1 and 0.
[0027] It will be appreciated that the slower response-time of the
sensor on the silicon substrate, .tau..sub.s may be more than one
or two orders of magnitude larger than the fast response-time
.tau..sub.f. Accordingly, for a fast response-time sensor e.g.,
membrane resistance 24, it is desirable to maximize the fast
response component in equation (4). This may be achieved by
increasing the isolation between the membrane and the bulk silicon
28. One possible means of increasing the isolation is by increasing
the membrane area. However, a large membrane may not be desirable
because it becomes more fragile and easily subject to fatigue and
breakage, and it would therefore significantly reduce the
durability of the device. Another methodology, such as that
disclosed herein in an exemplary embodiment is to take advantage of
the distinctions between the membrane response and the response due
to the silicon substrate 28.
[0028] Disclosed herein in an exemplary embodiment is an approach
where both types of detectors are used with corresponding
processing to extract the fast response component from the total
response. In an exemplary embodiment as depicted in FIGS. 3A and
3B, as well as FIGS. 4 and 5, two pairs of resistances R.sub.m 24
and R.sub.s 26 are employed in a configuration of a bridge as
illustrated and shown generally as 40. The bridge voltage V.sub.b
and the differential voltage .DELTA.V.sub.b respond differently to
a temperature step .DELTA.T. As demonstrated later in this
disclosure, these two signals may be combined in a novel and unique
way to extract the fast response component, thereby resulting in a
very fast response-time sensing scheme. Advantageously, employing
four resistances in a bridge 40 configuration facilitates
elimination of common errors and variations associated with the
resistances R.sub.m 24 and R.sub.s 26. Moreover, the bridge
configuration facilitates amplification of the differential voltage
generated by the two legs of the bridge 40.
[0029] When the bridge 40 of FIG. 4 is excited with a constant bias
current, denoted as I.sub.0, it may be shown that the bridge
voltage V.sub.b and the differential bridge voltage .DELTA.V.sub.b
are given by the following equations: V.sub.b=0.5 I.sub.0
(R.sub.m+R.sub.s) (6) .DELTA.V.sub.b=V.sub.1-V.sub.2=0.5 I.sub.0
(R.sub.m-R.sub.s) (7)
[0030] The step responses of these two signals are obtained by
replacing equations (4) and (5) in equations (6) and (7):
V.sub.b(b)=I.sub.0R.sub..alpha.+0.5 I.sub.0
.DELTA.R{(1-.alpha.[1-exp(-t/.tau..sub.f)]+(1+.alpha.)[1-exp(-t/.tau..sub-
.s)]} (8) .DELTA.V.sub.b(t)=0.5 I.sub.0
.DELTA.R(1-.alpha.){[1-exp(-t/.tau..sub.f)]-[1-exp(-t/.tau..sub.s)]}
(9) Through a linear combination of equations (8) and (9), it may
be noted that it is possible to cancel out the slowly varying
signal. Elimination of the slowly varying signal yields the fast
responding signal as desired. One implementation to facilitate
elimination of the slowly varying signal may be realized physically
with an electronic circuit as illustrated in FIG. 5 that sums the
bridge voltage V.sub.b and the differential voltage .DELTA.V.sub.b
after the latter has been amplified through an amplifier 50
exhibiting a gain G. The resulting sensor output voltage V.sub.0 of
the summer 60 is given by: V 0 .function. ( t ) = V b .function. (
t ) + G .times. .times. .DELTA. .times. .times. V b .function. ( t
) = I 0 .times. Ra + 0.5 .times. .times. I 0 .times. .DELTA.
.times. .times. R .times. { K 1 .function. [ 1 - exp .function. ( -
t / .tau. f ) ] + K 2 .function. [ 1 - exp .function. ( - t / .tau.
s ) ] } ( 10 ) ##EQU1## where K.sub.1=(1-.alpha.)(1+G),
K.sub.2=[2-(1-.alpha.)(1+G)] (11)
[0031] It is now shown that with an appropriate value for the gain
G, the slow varying term K.sub.2 in equation (10) vanishes. The
optimal value for the gain, G.sub.opt, is:
G.sub.opt=(1+.alpha.)/(1-.alpha.) (12) Using the optimal value for
the gain, equation (10) reduces to: V.sub.0opt(t)=I.sub.0
R.alpha.+I.sub.0 .DELTA.R [1-exp(-t/.tau..sub.f)] (13)
[0032] It will be appreciated that the functionality depicted in
FIG. 5 may also be readily computed with a processor such as with
controller 16. In another exemplary embodiment, controller 16
optionally receives the voltages from the bridge 40 for computation
in accordance with the teachings herein. It will be appreciated
that controller 40 may also receive signals indicative of the
voltages at nodes V.sub.1 and V.sub.2 in advance of the buffer
depicted for internal computation of .DELTA.V.sub.b.
[0033] Turning now to FIG. 6 as well, a flowchart depicting a
methodology 100 in accordance with an exemplary embodiment is
provided. At process block 102, the temperature signals 22 (FIG. 1)
are received from the bridge 40 (e.g., temperature sensor 20).
Optionally, a value for the voltage change for a given temperature
change, .DELTA.V.sub.b is computed from values for the voltages on
each leg of the bridge as depicted at optional process block 104.
At process block 106, the value for .DELTA.V.sub.b is scaled by
gain G, where G is preferably equal to G.sub.opt to facilitate
elimination of the slowly varying portion of the signal. Finally,
the optimal value V.sub.0opt(t) for the temperature including only
the rapidly varying portion may readily be computed by summing the
scaled value of .DELTA.V.sub.b with the bridge voltage V.sub.b in
accordance with Equation 13 as depicted at process block 108.
[0034] The disclosed invention can be embodied in the form of
computer or controller implemented processes and apparatuses for
practicing those processes. The present invention can also be
embodied in the form of computer program code containing
instructions embodied in tangible media 13, such as floppy
diskettes, CD-ROMs, hard drives, or any other computer-readable
storage medium, wherein, when the computer program code is loaded
into and executed by a computer or controller, the computer becomes
an apparatus for practicing the invention. The present invention
may also be embodied in the form of computer program code as a data
signal 15, for example, whether stored in a storage medium, loaded
into and/or executed by a computer or controller, or transmitted
over some transmission medium, such as over electrical wiring or
cabling, through fiber optics, or via electromagnetic radiation,
wherein, when the computer program code is loaded into and executed
by a computer, the computer becomes an apparatus for practicing the
invention. When implemented on a general-purpose microprocessor,
the computer program code segments configure the microprocessor to
create specific logic circuits.
[0035] It will be appreciated that the use of first and second or
other similar nomenclature for denoting similar items is not
intended to specify or imply any particular order unless otherwise
stated.
[0036] While the invention has been described with reference to an
exemplary embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *