Title of Invention

AN INTENSITY MODULATED OPTIC FIBER TEMPERATURE SWITCHING IMMERSION PROBE FOR REMOTE SENSING OF TEMPERATURE & SWITCHING OF AN INDUSTRIAL PROCESS THEREOF

Abstract An intensity modulated optic fiber temperature switching immersion probe for remote sensing of temperature, which comprises; a Y-shaped optical fiber light guide encased in a metallic sleeve (8) , the Y-guide having a source arm (2), detector arm (10), a Y-coupler (3), a common arm (9) and a common end cap(4); a light source is coupled to the said source arm; a photo-detector is aligned to the said detector arm; the said Y-guide fits into the said common end cap (4) of the said metal sleeve; an evacuated cell (6) containing a chemical is attached to the said common end of said Y-guide as means for sensing temperature; the said cell having a aluminum coating on the outside of the bottom surface forming a concave mirror; the said cell is covered with a glass plate (5)on the upper side; the said cell is further bonded and coupled to the said metal sleeve by means of a metallic ring(7); and a power meter being connected for the processing of electrical signal;
Full Text This invention relates to an intensity modulated optic fiber temperature switching immersion probe for remote sensing of temperature & switching of an industrial process thereof.
FIELD OF INVENTION
The present invention relates to an intensity modulated fiber temperature optic switching immersion probe for remote temperature monitoring and switching of an industrial process. The present invention also provides a method for remote sensing of temperature.
BACKGROUND OF THE INVENTION
Conventionally, thermometers, thermocouples and pyrometers are used to measure and control the temperature, but they are not immune to hostile, corrosive and electro-magnetically noisy environment. The novelty about this probe is the use of optical fibers in conjunction with a cell containing a chemical and resulting in a change of light level at its melting point. This arrangement overcomes the above mentioned problems effectively and provides the added advantage of remote monitoring. The cell is opaque to light at room temperature but becomes transparent at a given higher temperature enabling actuation of a relay to stop the heating process or raise an alarm. There is no electric signal being guided in this probe. It is only the light signal which is guided through optical fibers and is unaffected by the presence of electrical signals.
OBJECTS OF THE INVENTION
The main object of the present invention is to provide a reliable, durable, cost-effective and in-situ temperature switching fiber optic immersion probe, which overcomes most of the drawbacks present in conventional temperature probes as detailed above.
Another object of the present invention is to provide a method for remote sensing of temperature using this immersion probe.
Further object of the present invention is to provide an immersion probe for remote sensing temperature having a chemical that is non-toxic, non-inductive, non-conductive and non-corrosive.
Yet another object of the present invention is to provide an immersion probe for remote sensing of temperature in harsh working conditions.

SUMMARY OF THE INVENTION
The present invention relates to an intensity modulated fiber optic temperature switching immersion probe for remote temperature monitoring and switching of an industrial process. The present invention also provides a method for remote sensing of temperature. The present invention adopts a method wherein the melting of point of the chemical substance determines the switching mode for the device. DETAILED DESCRIPTION OF THE INVENTION
Accordingly, the present invention provides An intensity modulated optic fiber temperature switching immersion probe for remote sensing of temperature, which comprises;
(a) a Y-shaped optical fiber light guide encased in a metallic sleeve(8) terminated with a metallic end cap (1);
(b) the Y-guide having a source arm (2), detector arm (10), a Y-coupler (3), a common arm (9) and a common end cap(4);
(c) a light source is coupled to the said source arm;
(d) a photo-detector is aligned to the said detector arm;
(e) the said Y-guide fits into the said common end cap (4) of the said metal sleeve;
(f) an evacuated cell (6) containing a chemical is attached to the said common end of said Y-guide as means for sensing temperature;
(g) the said cell having a aluminum coating on the outside of the bottom surface forming a concave mirror;
(h) the said cell is covered with a glass plate (5)on the upper side;
(i) the said cell is further bonded and coupled to the said metal sleeve by means of a metallic ring(7); and
(j) a power meter being connected for the processing of electrical signal; An embodiment of the present invention, wherein the Y-shaped optic guide is encased in a crush resistant metallic sleeve.
Yet another embodiment of the present invention, wherein the optical fiber is made of dielectric material that is non-corrosive, durable and immune to any Electro Magnetic Interference (EMI) and RFI.(Radio Frequency Interference)
Still another embodiment of the present invention, wherein the light source is white
light.
Yet another embodiment of the present invention, wherein the detector arm that is
coupled to a photo-detector is connected to signal processing electronic circuitry and


an output display.
Still another embodiment of the present invention, wherein the chemical used
undergoes phase transformation from solid to a liquid phase at its melting point.
Yet another embodiment of the present invention, wherein the chemical is selected
from oxalic acid, sodium chloride, paraffin wax and preferably acetamide.
Further embodiment of the present invention, wherein the chemical is non-toxic, noncorrosive
and non-inflammable.
Still another embodiment of the present invention, wherein in solid state the chemical
is opaque to light and emits a fixed value of optical output and with the increased
temperature the chemical melts and becomes transparent thus generating an increased
optical output.
Yet another embodiment of the present invention, wherein the phase transformation at
the melting point of the chemical increases the optical output that is used as a detector
signal for actuation of alarm or relay.
Further embodiment of the present invention, wherein the length of the cell is twice
the focal length of the concave mirror.
Still another embodiment of the present invention, wherein the optical signal
propagation is secure and without any cross talk or interference problems.
Yet another embodiment of the present invention, wherein the optical signal is
unaffected by the presence of electrical signals.
Still another embodiment of the present invention, wherein the said probe is used for
remote sensing of temperature upto a distance of 1 km.
Further embodiment of the present invention, wherein the said probe at an increased
temperature provides an increase of 6 times in the output signal over the signal at the
room temperature.
Yet another embodiment of the present invention, wherein said optical probe operates
at the melting temperature of the chemical that is in the range of 75-85 ° C.
Further embodiment of the present invention, wherein said optical probe is used in
monitoring temperature in hostile, inflammable, corrosive and electro-magnetically
noisy environments, preferably in petrochemical industries and power plants.
The present invention also provides a method of sensing temperature through
intensity modulation of light signal using an intensity modulated and remote sensing
optic fiber temperature switching immersion probe, said method comprising the steps
of:
(a) immersing the probe in a liquid container having a temperature below the
melting point of the chemical;
(b) recording a fixed value of optical signal generated by the chemical in solid
state and at the room temperature; and
(c) detecting the maximum optical signal generated by the chemical at its melting
point and in liquid phase;
(d) detecting the optical signal be means of a photo-detector;
(e) signal processing by means of an electronic circuitry; and
(f) enabling actuation of a relay to stop the heating process or raise an alarm.
An embodiment of the present invention, a method wherein the liquid is selected from
the group consisting of water, acetone, carbon tetrachloride and transformer oil.
Another embodiment of the present invention, a method wherein the chemical is
selected from selected from oxalic acid, sodium chloride, paraffin wax and preferably
acetamide.
Still another embodiment of the present invention, a method wherein the chemical
having a melting point in the range of 75-85 °C.
Yet another embodiment of the present invention, a method wherein the optical signal
propagation is secure and without any cross talk or interference problems.
Still another embodiment of the present invention, a method wherein the optical
signal is unaffected by the presence of electrical signals.
Yet another embodiment of the present invention, a method wherein the said probe is
used for remote sensing upto a distance of 1 km.
Still another embodiment of the present invention, a method wherein the said probe at
an increased temperature provides an increase of 6 times in the output signal over the
signal at the room temperature.
Yet another embodiment of the present invention, a method wherein the chemical
substance that is opaque at room temperature becomes transparent at a given higher
temperature enabling actuation of a relay to stop the heating process or raise an alarm.
The invention is further explained in the form of the following embodiments.
In the present invention a fiber optic temperature switching probe, which comprises a
fiber optic Y-shaped light guide and a small cc'l containing a special chemical/which
undergoes solid to liquid phase transformation at its melting point. The cell has a
concave mirror on its lower side and a glass plate on the upper side. The chemical
identified and experimented for this probe undergoes phase change at a temperature of
78-79 °C. A small amount of the chemical is first transferred into cell and then it is
evacuated and properly sealed. The cell is further bonded to a metal tube, which fits
tightly on to the common end cap of the Y-guide. A metallic ring is used for coupling
the cell to the metal tube. The Y-guide has two arms, termed as a source arm and the
detector arm. A white light source is coupled to the source arm while the detector arm
is aligned to a PIN photo-detector. The electrical signal is processed and displayed by
a powermeter.
In an embodiment of the present invention a suitable chemical has been identified and
used to realize the cell for the temperature switching probe. Depending on the
identification of a suitable chemical e.g. non-corrosive, non-inflammable, switch
probes for different temperatures can be realized.
In another embodiment of the present invention, fiber optic light guides have been
employed which are made of optical glass, a highly durable material being nonconductive
and non-inductive in nature.
The sensing signal is in the form of intensity modulated light guided by the fiber. The
signal propagation is secure without any cross talk or interference problems.
The optical fiber temperature switch probe comprises of an indigenously produced Y--
shaped optical fiber light guide/bundle encased in a crush-resistant metallic sleeve
with its ends properly terminated into metallic end caps. A few grams of the
commercially available chemical in grainy form is first vacuum dried under clean
conditions and then transferred into the cell made from a thin-walled glass test tube.
The curved surface at the bottom of the test tube is given a reflective aluminum
coating on the outside as to realize a concave mirror while the upper end is covered
with a plane glass disc. Considering the image formation characteristics, the length of
the cell is chosen to be twice the focal length of the concave mirror. Proper adhesive
sealing is done to make the cell airtight.
With the help of a metallic ring, the cell is firmly coupled onto the common end cap
of the Y-guide and in this situation, the common end rests on to the top glass cover of
the cell.
When the probe is immersed in a liquid container at a temperature below the melting
point of the chemical, there is a fixed value of the detector signal. The chemical
begins to melt as the temperature reaches around 78-79°C and thus more light reaches
the detector resulting in an increased output signal. This continues till the chemical
has melted completely and the detector signal has attained a maximum value which
takes place at about 83 °C. The probe provides typically 6 times increase in the output
signal as compared to the room temperature stage. At any particular value of
temperature in this range (75-85 °C) corresponding to the level of optical signal
available, either an alarm signal could be generated or the process can be shut down
automatically as to stop further heating of the liquid/solvent. Thus the probe can be
used as a temperature switch e.g. to stop the process from further heating at any value
of temperature in this range.
The probe facilitates sensing of temperature through intensity modulation of light
signal. This modulation process is unaffected by a hostile and electrically noisy
environment whereas the prior art has to be either properly shielded for gaining this
immunity or protection. This is so because optical fibers are made from dielectric
materials and therefore, they are both non-inductive and non-conductive in nature
thereby bringing immunity to EMI/RFI. Also the basic raw material, optical glass
from which fibers are made is quite durable and effectively withstands harsh and
corrosive environments encountered in various application areas.
When the probe end is dipped into a liquid whose temperature is to be monitored, the
optical signal reaching the detector depends on the transparency to light provided by
the cell medium. As the temperature rises, the chemical starts melting beyond a point
and transparency to light goes up rapidly thus increasing the detector signal. At a
stage, the signal reaches its maximum value when the entire chemical has melted.
This level of the signal can be used to raise an alarm or actuate a relay/switch to shut
down or start a process at that maximum value of temperature thus working as a
temperature switch probe.
This temperature switch probe has been experimented in the laboratory by dipping it
in water and other solvents such as acetone, carbon tetrachloride, transformer oil etc
to monitor their temperature. The temperature of water and other liquids is recorded
with a mercury thermometer. There has been consistency and repeatability in the
optical output with temperature within 1°C.
This probe could be beneficially used for starting/closing of a process in an industry.
The process monitoring can be carried out remotely by extending the length of optical
fiber arms of the bundle. It can be quite a durable and cost-effective device and the
process monitoring operation can be made automatic.
A comparison between the present probe and the conventional temperature measuring
techniques/ probes is given below:
COMPARISON CHART
S.No
1.
2.
3.
THERMOMETER
No point switching
Immunity to EMI/ RFI
and hostile / corrosive
environments
No remote sensing
THERMOCOUPLE
No point switching
Not immune to EMI/
RFI and hostile /
corrosive environments
No remote sensing
PYROMETER
No point
switching
Not immune to
EMI/ RFI and
hostile / corrosive
environments
Remote sensing
(few 10s of
meters)
FIBER OPTIC
PROBE
Point switching
Immunity to EMI/
RFI and hostile /
corrosive
environments
Remote sensing
(upto a Km)
ADVANTAGES
1. It can work for process industry applications where the environment is hostile and
electrically noisy.
2. It can monitor the temperature remotely and the process can be made automatic.
3. A low cost and durable device.
4. The immersion probe is a simple and useful device, which can be employed in
harsh environments for in-situ temperature switching applications from a remote
location.
The drawings provided in the enclosed sheets indicate the configuration of the fiber
optic temperature switching immersion probe. It basically comprises of a Y-shaped
fiber optic bundle and a small cell made of a thin-walled glass test tube containing a
chemical. The bottom surface of the test tube has been given a protective reflective
aluminum coating on the outside for realizing as a concave mirror. The Y-shaped
fiber optic bundle contains two arms: the source arm and the detector arm. A white
light source is coupled to source arm employing suitable optics while the other arm is
aligned to a PIN photo-detector.
The various parts of the probe have been labeled as under:
1. End Cap for Coupling to the Light Source
2. Source Arm
8
3. Y-Coupler
4. Common End Cap of the Fiber Bundle
5. Reflective Coating on Outside of the Bottom Surface of the Thin-Walled Glass
Cell
6. Cell Containing the Chemical
7. Metallic Ring for Coupling Cell to the Common End Cap
8. Metallic Tube Tightly Fitting the Common End Cap
9. Common Arm
10. Detector Arm

We claim:
1. An intensity modulated optic fiber temperature switching immersion probe for
remote sensing of temperature, which comprises;
(k) a Y-shaped optical fiber light guide encased in a metallic sleeve(8) terminated
with a metallic end cap (1); (1) the Y-guide having a source arm (2), detector arm (10), a Y-coupler (3), a
common arm (9) and a common end cap(4); (m) a light source is coupled to the said source arm; (n) a photo-detector is aligned to the said detector arm; (o) the said Y-guide fits into the said common end cap (4) of the said metal
sleeve; (p) an evacuated cell (6) containing a chemical is attached to the said common
end of said Y-guide as means for sensing temperature; (q) the said cell having a aluminum coating on the outside of the bottom surface
forming a concave mirror; (r) the said cell is covered with a glass plate (5)on the upper side; (s) the said cell is further bonded and coupled to the said metal sleeve by means
of a metallic ring(7); and (t) a power meter being connected for the processing of electrical signal;
2. A probe as claimed in claim 1, wherein the Y-shaped optic guide is encased in a crush resistant metallic sleeve.
3. A probe as claimed in claim 1, wherein the optical fiber is made of dielectric material that is non-corrosive, durable and immune to any Electro Magnetic Interference (EMI) and RFI and RFI (Radio Frequency Interference).
4. A probe as claimed in claim 1, wherein the light source is white light.
5. A probe as claimed in claim 1, wherein the detector arm that is coupled to a photo-detector is connected to signal processing electronic circuitry and an output display.
6. A probe as claimed in claim 1, wherein the chemical selected from chemical which undergoes phase transformation from solid to a liquid phase at its melting point.
7. A probe as claimed in claim 1, wherein the chemical is selected from oxalic acid, sodium chloride, paraffin wax and preferably acetamide.
8. A probe as claimed in claims 1 and 7, wherein the chemical is non-toxic, non-

corrosive non- conductive and non-inductive in nature and non-inflammable.
9. A probe as claimed in claim 1 and 7, wherein in solid state the chemical is opaque to light and emits a fixed value of optical output and with the increased temperature the chemical melts and becomes transparent thus generating an increased optical output.
10. A probe as claimed in claim 1 and 7, wherein the phase transformation at the melting point of the chemical increases the optical output that is used as a detector signal for actuation of alarm or relay.
11. A probe as claimed in claim 1, wherein the length of the cell is twice the focal length of the concave mirror which is formed by the internal surface of the bottom of test tube coated outside by aluminium.
12. A probe as claimed in claim 1, wherein the said probe is used for remote sensing of temperature upto a distance of 1 km.
13. A probe as claimed in claim 1, wherein the said probe at an increased temperature provides an increase of 6 times in the output signal over the signal at the room temperature.
14. A probe as claimed in claim 1, wherein said optical probe operates at the melting temperature of the chemical that is in the range of 75-85 °C.
15. A process of sensing temperature using the probe as claimed in claim 1, which comprises:

(a) immersing the said probe in a liquid container having a temperature below the melting point of the chemical;
(b) recording a fixed value of optical signal generated by the chemical in solid state and at the room temperature; and
(c) detecting the maximum optical signal generated by the chemical at its melting point and in liquid phase;
(d) detecting the optical signal be means of a photo-detector;
(e) signal processing by means of an electronic circuitry; and
(f) enabling actuation of a relay to stop the heating process or raise an alarm.

16. A process according to claim 15, wherein the liquid is selected from the group consisting of water, acetone, carbon tetrachloride and transformer oil.
17. A process according to claim 15, wherein the chemical is selected from selected from oxalic acid, sodium chloride, paraffin wax and preferably acetamide.
18. A process according to claim 15, wherein the chemical having a melting point in
the range of 75-85 °C.

19. A process according to claim 15, wherein the said probe is used for remote sensing upto a distance of 1 km.
20. A process according to claim 15, wherein the said probe at an increased temperature provides an increase of 6 times in the output signal over the signal at the room temperature.
21. A process according to claim 15, wherein the chemical substance that is opaque at room temperature becomes transparent at a given higher temperature enabling actuation of a relay to stop the heating process or raise an alarm.
22. An intensity modulated optic fiber temperature switching immersion probe for remote sensing of temperature substantially as herein describe with reference to examples and figure! accompanying this specification.

Documents:

2371-DELNP-2004-Abstract-(11-09-2009).pdf

2371-delnp-2004-abstract.pdf

2371-DELNP-2004-Claims-(11-09-2009).pdf

2371-delnp-2004-claims.pdf

2371-DELNP-2004-Correspondence-Others-(11-09-2009).pdf

2371-delnp-2004-correspondence-others.pdf

2371-DELNP-2004-Description (Complete)-(11-09-2009).pdf

2371-delnp-2004-description (complete).pdf

2371-delnp-2004-drawings.pdf

2371-DELNP-2004-Form-1-(11-09-2009).pdf

2371-delnp-2004-form-1.pdf

2371-delnp-2004-form-18.pdf

2371-DELNP-2004-Form-2-(11-09-2009).pdf

2371-delnp-2004-form-2.pdf

2371-DELNP-2004-Form-3-(11-09-2009).pdf

2371-delnp-2004-form-3.pdf

2371-DELNP-2004-Form-5-(11-09-2009).pdf

2371-delnp-2004-form-5.pdf

2371-DELNP-2004-Petition-137-(15-09-2009).pdf


Patent Number 259728
Indian Patent Application Number 2371/DELNP/2004
PG Journal Number 13/2014
Publication Date 28-Mar-2014
Grant Date 26-Mar-2014
Date of Filing 13-Aug-2004
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110 001, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 NAHAR SINGH COHERENT OPTICS DIV. C S I O, SECTOR-30, CHANDIGARH-160 030(INDIA)
2 SUBHASH CHANDER JAIN COHERENT OPTICS DIV. C S I O SECTOR-30, CHANDIGARH-160 030(INDIA)
3 ANIL KUMAR AGGARWAL COHERENT OPTICS DIV. C S I O SECTOR-30, CHANDIGARH-160 030(INDIA)
PCT International Classification Number GO1K 11/06
PCT International Application Number PCT/IN02/00075
PCT International Filing date 2002-03-27
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/108,593 2002-03-28 U.S.A.