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Infrared Thermometer Theory
BUY HIGH QUALITY INFRARED THERMOMETERS
What is an Infrared thermometers? It is a device that measures temperature using blackbody radiation (generally infrared) emitted from objects that lie above a temperature of 0 degrees Kelvin.
They are sometimes called laser IR thermometers if a laser is used to help aim the thermometer, or non-contact thermometers
to describe the device’s ability to measure temperature from a
distance. By knowing the amount of infrared energy emitted by the
object and its emissivity, the object's temperature can be determined.
The most basic design consists of a lens to focus the infrared energy on to a ir detector, which converts the energy to an electrical signal
that can be displayed in units of temperature after being adjusted
for ambient temperature variation. This configuration facilitates
temperature measurement from a distance without
contact with the object to be measured. As such, the infrared
thermometer is useful for measuring temperature under circumstances
where thermocouples
or other probe type sensors cannot be used because the user can not get
physically close to the object to measure its temperature because it is
not accessible for some reason.
Some typical circumstances are where the object to be measured is moving; where the object is surrounded by an electromagnetic field, as in induction heating ; where the object is contained in a vacuum or other controlled atmosphere; or in applications where a fast response is required.
Infrared
thermometers can be used to serve a wide variety of temperature
monitoring functions. A few examples provided to this article include:
- Detecting clouds for remote telescope operation
- Checking mechanical equipment or electrical circuit breaker boxes or outlets for hot spots
- Checking heater or oven temperature, for calibration and control purposes
- Detecting hot spots / performing diagnostics in electrical circuit board manufacturing
- Checking for hot spots in fire fighting situations
- Monitoring
materials in process of heating and cooling, for research and
development or manufacturing quality control situations
Additional Applications for Infrared Thermometers
There
are many varieties of infrared temperature sensing devices available
today, including configurations designed for flexible and portable
handheld use, as well many designed for mounting in a fixed position to
serve a dedicated purpose for long periods.
Specifications
of portable handheld sensors available to the home user will include
ratings of temperature accuracy (usually plus or minus a degree or two
and othe parameters. The distance-to-spot ratio (D:S) is the ratio of
the distance to the object and the diameter of the temperature
measurement area. For instance if the D:S ratio is 12:1, measurement of
an object 12 inches away will average the temperature over a 1-inch
diameter circular area. The sensor may have an adjustable emissivity
setting, which can be set to measure the temperature of reflective
(shiny) and non-reflective surfaces. A non-adjustable thermometer can
be used to measure the temperature of a shiny surface by applying a
non-shiny paint or tape to the surface.
Useful Emissivity values for exacting IR Measurement applications may be found in the following table.
Emissivity Table
Since the emissivity of a
material will vary as a function of temperature and surface finish, the
values in this table should be used only as a guide for relative or
delta measurements. The exact emissivity of a material should be
determined when absolute measurements are required.
| Material |
°F |
°C |
EMS |
| METALS |
ALLOYS: 20~Ni, 24~CR,
55~FE, Oxid. |
392 |
200 |
.9 |
| 20~Ni, 24~CR, 55~FE, Oxid. |
932 |
500 |
.97 |
| 60~Ni , 12~CR, 28~FE, |
518 |
270 |
.89 |
| 60~Ni , 12~CR, 28~FE,. |
1040 |
560 |
.82 |
| 80~Ni, 20~CR, Oxidized |
212 |
100 |
.87 |
| 80~Ni, 20~CR, Oxidized |
1112 |
600 |
.87 |
| 80~Ni, 20~CR, Oxidized |
2372 |
1300 |
.89 |
| ALUMINUM: Unoxidized |
77 |
25 |
.02 |
| Unoxidized |
212 |
100 |
.03 |
| Unoxidized |
932 |
500 |
.06 |
| Oxidized |
390 |
199 |
.11 |
| Oxidized |
1110 |
599 |
.19 |
| Oxidized at 599°C |
390 |
199 |
.2 |
| Oxidized at 599°C |
1110 |
599 |
.31 |
| Heavily Oxidized |
200 |
93 |
.09 |
| Heavily Oxidized |
940 |
504 |
.18 |
| Highly Polished |
212 |
100 |
.09 |
| Roughly Polished |
212 |
100 |
.04 |
| Commercial Sheet |
212 |
100 |
.06 |
| Highly Polished Plate |
440 |
227 |
.04 |
| Highly Polished Plate |
1070 |
577 |
.05 |
| Bright Rolled Plate |
338 |
170 |
.04 |
| Bright Rolled Plate |
932 |
500 |
.05 |
| Alloy A3003, Oxidized |
600 |
316 |
.4 |
| Alloy A3003, Oxidized |
900 |
482 |
.4 |
| Alloy 1100~0 |
200~800 |
93~427 |
.05 |
| Alloy 24ST |
75 |
24 |
.09 |
| Alloy 24ST, Polished |
75 |
24 |
.09 |
| Alloy 75ST |
75 |
24 |
.11 |
| Alloy 75ST, Polished |
75 |
24 |
.08 |
| Alloy 75ST, Polished |
176 |
80 |
.34 |
| Bismuth, Unoxidized |
77 |
25 |
.05 |
| Bismuth, Unoxidized |
212 |
100 |
.06 |
| BRASS: 73% Cu, 27% Zn, Polished |
476 |
247 |
.03 |
| 73% Cu, 27% Zn, Polished |
674 |
357 |
.03 |
| 62% Cu, 37% Zn, Polished |
494 |
257 |
.03 |
| 62% Cu, 37% Zn, Polished |
710 |
377 |
.04 |
| 83% Cu, 17% Zn, Polished |
530 |
277 |
.03 |
| MATT |
68 |
20 |
.07 |
| Burnished to Brown Colour |
68 |
20 |
.4 |
| Cu~Zn, Brass Oxidized |
392 |
200 |
.61 |
| Cu~Zn, Brass Oxidized |
752 |
400 |
.6 |
| Cu~Zn, Brass Oxidized |
1112 |
600 |
.61 |
| Unoxidized |
77 |
25 |
.04 |
| Unoxidized |
212 |
100 |
.04 |
| Cadmium |
77 |
25 |
.02 |
| CARBON: Lampblack |
77 |
25 |
.95 |
| Unoxidized |
77 |
25 |
.81 |
| Unoxidized |
212 |
100 |
.81 |
| Unoxidized |
932 |
500 |
.79 |
| Candle Soot |
250 |
121 |
.95 |
| Filament |
500 |
260 |
.95 |
| Graphitized |
212 |
100 |
.76 |
| Graphitized |
572 |
300 |
.75 |
| Graphitized |
932 |
500 |
.71 |
| Chromium |
100 |
38 |
.08 |
| Chromium |
1000 |
538 |
.26 |
| Chromium, Polished |
302 |
150 |
.06 |
| Cobalt, Unoxidized |
932 |
500 |
.13 |
| Cobalt, Unoxidized |
1832 |
1000 |
.23 |
| Columbium, Unoxidized |
1500 |
816 |
.19 |
| Columbium, Unoxidized |
2000 |
1093 |
.24 |
| COPPER: Cuprous Oxide |
100 |
38 |
.87 |
| Cuprous Oxide |
500 |
260 |
.83 |
| Cuprous Oxide |
1000 |
538 |
.77 |
| Black, Oxidized |
100 |
38 |
.78 |
| Etched |
100 |
38 |
.09 |
| Matte |
100 |
38 |
.22 |
| Roughly Polished |
100 |
38 |
.07 |
| Polished |
100 |
38 |
.03 |
| Highly Polished |
100 |
38 |
.02 |
| Rolled |
100 |
38 |
.64 |
| Rough |
100 |
38 |
.74 |
| Molten |
1000 |
538 |
.15 |
| Molten |
1970 |
1077 |
.16 |
| Molten |
2230 |
1221 |
.13 |
| Nickel Plated |
100~500 |
38~260 |
.37 |
| Dow Metal |
.4~600 |
~334 |
.15 |
| GOLD: Enamel |
212 |
100 |
.37 |
| Plate on .0005 Silver |
200~750 |
93~399 |
.11~.14 |
| Plate on .0005 Nickel |
200~750 |
93~399 |
.07~.09 |
| Polished |
100~500 |
38~260 |
.02 |
| Polished |
1000~2000 |
538~1093 |
.03 |
| HAYNES ALLOY C: Oxidized |
600~2000 |
316~1093 |
.90~.96 |
| HAYNES ALLOY 25: Oxidized |
600~2000 |
316~1093 |
.86~.89 |
| HAYNES ALLOY X: Oxidized |
600~2000 |
316~1093 |
.85~.89 |
| Inconel Sheet |
1000 |
538 |
.28 |
| Inconel Sheet |
1200 |
649 |
.42 |
| Inconel Sheet |
1400 |
760 |
.58 |
| Inconel X, Polished |
75 |
24 |
.19 |
| Inconel B, Polished |
75 |
24 |
.21 |
| IRON: Oxidized |
212 |
100 |
.74 |
| Oxidized |
930 |
499 |
.84 |
| Oxidized |
2190 |
1199 |
.89 |
| Unoxidized |
212 |
100 |
.05 |
| Red Rust |
77 |
25 |
.7 |
| Rusted |
77 |
25 |
.65 |
| Liquid |
2760~3220 |
1516~1771 |
.42~.45 |
| CAST IRON: Oxidized |
390 |
199 |
.64 |
| Oxidized |
1110 |
599 |
.78 |
| Oxidized |
212 |
100 |
.21 |
| Strong Oxidation |
40 |
104 |
.95 |
| Strong Oxidation |
482 |
250 |
.95 |
| Liquid |
2795 |
1535 |
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