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Infrared History |
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A simple but interesting
history of Infrared Thermometers
Version 017
Copyright 2000-2004
www.ZyTemp.com
--- All Rights Reserved ---
Reproduction of this document in whole or in part is permitted
if both of the following conditions are satisfied:
This notice is included in its entirety at the beginning.
There is no charge except to cover the costs of copying.
Disclaimer:
It is very difficult to prove the accuracy of the order
of inventions, so we have adopted the file dates of patents
for our chronology.
ZyTemp accepts no legal or academic responsibilities for
the true first inventor. |
1884,
The beginning
Stefan-Boltzmann's Law of black body radiation:
In 1884, L.E. Boltzmann showed how Josef Stefan's
empirical T4 Black Body Radiation Law, formulated
in 1879, could be derived from the physical principles
of thermodyamics.
Boltzmann's findings were elegant, yet simple:
Radiation Power = Temperature4 x Constant
Consequently, Boltzmann has been named as the father
of infrared thermometry.
In infrared thermometers, a small CPU inside the
device uses this formula to accurately predict the
temperature of a target.
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Figure 1: LE Boltzmann(1844-1906) |
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1892, The disappearing-filament optical pyrometer
The earliest infrared thermometer (IRT) was known as
the disappearing-filament optical pyrometer.
The glowing brightness of a heated surface as a means
for measuring temperature was first suggested by Becquerel
in 1836, but it was not until 1892 that the French industrialist
Le ChateLier introduced the first laboratory radiation
thermometer.[1]
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1899,
The first patent for disappearing-filament optical pyrometer:
The first patent for the optical pryometer was granted
to Morse in 1899. Holborn and Kurlbaum, apparently unaware
of the Morse patent, independently developed a similar
disappearing-filament optical pyrometer in 1901.
Figure 2: Morse's patent
: the disappearing-filament pyrometer (1899)
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In Morse's improved apparatus some difficulties of previous
optical pyrometer are overcome by so organizing the same
as to permit a comparison based on the fact that if two
substances are made to produce in the eye the same color
effects or sensations and one of them, or a portion thereof
is arranged in the path of the rays passing from the other
to the eye the portion of the one so arranged or superposed
will merge in the other and apparently be obliterated
from view.
The Leeds&Northrup Company acquired the Morse's patent
of 1899 and in 1917 produced a commercially available
disappearing-filament optical pyrometer similar to the
one developed by Holburn and Kurlbaum.
However, one of the main disadvantages of the disappearing-filament
optical pyrometer (even till today) is its large size
and need for an attendant for operation. They are still
in use today because of their high degree of accuracy
and useful functionality.
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1913,
If the Titanic were able to detect icebergs.....
We are reminded of how the Titanic sank after striking
an iceberg, but is there a way that we can show such a
disaster could have been avoided?
L. Bellingham presented a method
to detect the presence of icebergs and steamships by
using a mirror and the original thermopile. He later
patented this device in 1913. His infrared thermometer's
primary advantage over the disappearing-filament optical
pyrometer was that it was able to detect temperatures
substantially lower than ambient. If the Titanic crew
had this device on hand, they would have been able to
steer clear of their grave tragedy!
Figure 3: Bellingham's
Infrared Thermometer(1913)
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1931, Finally, a practical
commercial product
In addition to their accomplishments in 1917, the Leeds&Northrup
Company introduced the first commercially-available total
radiation thermometer.
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1968,
Emissivity altered
The evolution of the IRT came about in various forms.
One of these embodiments is described in the patent shown
in Figure 4:
The file date is 1968 July, it's still an analog; heavy
device, with bulky shutter (or chopper), require long
time to stabilized. this device uses the pyroelectric
crystal as detector.
Figure 4: Pyrometer
employing a pyroelectric crystal detector |
US3586439: DIRECT READING PYROMETER EMPLOYING PYROELECTRIC
CRYSTAL DETECTOR
Country: United States of America
Inventor: Treharne, Richard W.; Xenia, OH
Assignee: Kettering Scientific Research, Inc.
Published / Filed: 1971-06-22 / 1968-07-15
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1973, The development
of the short range IRT
In 1973, a short range IRT was created by Sensors, Inc.
It utilized a pointer to identify the exact location of
measurement. Figure 5 shows the IRT:
Figure 5: Apparatus for
IR radiation temperature measurement |
Title: US3777568: D. C. ELECTRONIC APPARATUS FOR IR RADIATION
TEMPERATURE MEASUREMENT
Inventor: Risgin, Ojars; Grass Lake, MI
Szeles, Donald M.; Ann Arbor, MI
Assignee: Sensors, Inc., Ann Arbor, MI
Published / Filed: 1973-12-11 / 1971-12-21
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1977, Revolution of
a sensor: the miniature thermopile
It has been known that evaporating overlapping films of
antimony and bismuth could form thermocouples. Since this
construction is more rugged than that of the traditional
thermopile, it became advantageous that this method be
applied for the construction of thermopiles. This would
lead to a significant development of the thermopile for
space applications because of its small critical mass.
Overlapping areas that form the junction (hot) are fashioned
on a thermally insulating layer set, or cold junction,
in the middle of an aluminum block, which served as a
heat sink. A reference junction is formed where the evaporated
films come in contact with the aluminum block. Since the
junctions have a very low specific heat, the time constant
of an evaporated thermopile can be as short as 10 milliseconds.
Furthermore, this evaporation technique allows the thermopile
to be easily conformed to any size or shape.[2]
Figure 6 shows the first miniature radiation thermopile,
its sensor is smaller than 4mm2.
The first miniature infrared sensor, before this invention,
the infrared sensor is as large as a coin.
Now, it can be smaller than a bean (4mm).
Figure 6: Small high-performance
radiation thermopile. |
Title: US4111717: Small-size high-performance radiation
thermopile
Inventor: Baxter, Ronald Dale; Furlong, PA
Assignee: Leeds & Northrup Company, North Wales,
PA
Published / Filed: 1978-09-05 / 1977-06-29
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1984, 6,000,000pcs
of Infrared Thermometer for ear
In 1984, a major milestone occurred for infrared thermometers.
IRT applications were soon found in the hospital, home,
and ear! One of the turning point applications - the infrared
ear thermometer - resulted in the sale of six million
pieces, and consequently a substantial drop in the IRT's
sensor cost.
This remarkable invention (USP4602642), has continued
to evolve, and continues to thrive in the market today.
Figure 7a/b show the original patent
and modern day product:
Figure 7ab: Original
picture of patent |
Figure 7b: Modern day
picture |
US4602642: Method and apparatus for measuring internal
body temperature utilizing infrared emissions
Inventor: O'Hara, Gary J.; Escondido, CA ; Phillips, David
B.; San Diego, CA
Assignee: Intelligent Medical Systems, Inc., Carlsbad,
CA
Published / Filed: 1986-07-29 / 1984-10-23
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2002, The Most compact
Infrared Thermometer
In July 2002, ZyTemp introduced the world's smallest infrared
thermometer (IRT), the TN105. The TN1 is as small as the
battery of some of today's IRTs, and with it's anti-thermal
shock capability, it can handily outperform traditional
counterparts (You can put 2~4pcs into your shirt pocket.)
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2003, Infrared meets
Thermocouple
In July 2003, ZyTemp unveiled the TCT1, a low cost, high
value infrared + thermocouple thermometer. In this design,
non-contact and contact functionalities are conjoined
to produce a dual utility of instant results (infrared)
and high accuracy (thermocouple).
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Reference
[1]D.P.DeWitt "Theory and practice of radiation thermometer"
P13-P15
[2] Richard D. HUDSON, JR "Infrared System Engineering"
P272
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