32
Thermographic measurement
techniques
32.1
Introduction
An infrared camera measures and images the emitted infrared radiation from an object.
The fact that radiation is a function of object surface temperature makes it possible
for the camera to calculate and display this temperature.
However, the radiation measured by the camera does not only depend on the tem-
perature of the object but is also a function of the emissivity. Radiation also originates
from the surroundings and is reflected in the object. The radiation from the object
and the reflected radiation will also be influenced by the absorption of the atmosphere.
To measure temperature accurately, it is therefore necessary to compensate for the
effects of a number of different radiation sources. This is done on-line automatically
by the camera. The following object parameters must, however, be supplied for the
camera:
■
The emissivity of the object
■
The reflected apparent temperature
■
The distance between the object and the camera
■
The relative humidity
■
Temperature of the atmosphere
32.2
Emissivity
The most important object parameter to set correctly is the emissivity which, in short,
is a measure of how much radiation is emitted from the object, compared to that from
a perfect blackbody of the same temperature.
Normally, object materials and surface treatments exhibit emissivity ranging from
approximately 0.1 to 0.95. A highly polished (mirror) surface falls below 0.1, while an
oxidized or painted surface has a higher emissivity. Oil-based paint, regardless of
color in the visible spectrum, has an emissivity over 0.9 in the infrared. Human skin
exhibits an emissivity 0.97 to 0.98.
Non-oxidized metals represent an extreme case of perfect opacity and high reflexivity,
which does not vary greatly with wavelength. Consequently, the emissivity of metals
is low – only increasing with temperature. For non-metals, emissivity tends to be high,
and decreases with temperature.
32
Publ. No. 1558550 Rev. a557 – ENGLISH (EN) – October 7, 2011
263
Содержание B6 series
Страница 2: ......
Страница 4: ......
Страница 6: ......
Страница 8: ......
Страница 9: ...User s manual Publ No 1558550 Rev a557 ENGLISH EN October 7 2011...
Страница 12: ...INTENTIONALLY LEFT BLANK xii Publ No 1558550 Rev a557 ENGLISH EN October 7 2011...
Страница 22: ...INTENTIONALLY LEFT BLANK 1 4 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 1 Warnings Cautions...
Страница 24: ...INTENTIONALLY LEFT BLANK 2 6 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 2 Notice to user...
Страница 26: ...INTENTIONALLY LEFT BLANK 3 8 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 3 Customer help...
Страница 28: ...INTENTIONALLY LEFT BLANK 4 10 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 4 Documentation updates...
Страница 36: ...INTENTIONALLY LEFT BLANK 7 18 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 7 Quick Start Guide...
Страница 60: ...INTENTIONALLY LEFT BLANK 12 42 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 12 Pairing Bluetooth devices...
Страница 86: ...INTENTIONALLY LEFT BLANK 13 68 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 13 Handling the camera...
Страница 112: ...INTENTIONALLY LEFT BLANK 15 94 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 15 Working with fusion...
Страница 124: ...INTENTIONALLY LEFT BLANK 16 106 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 16 Working with measurement tools...
Страница 142: ...INTENTIONALLY LEFT BLANK 19 124 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 19 Annotating images...
Страница 144: ...INTENTIONALLY LEFT BLANK 20 126 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 20 Programming the camera...
Страница 172: ...INTENTIONALLY LEFT BLANK 23 154 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 23 Cleaning the camera...
Страница 192: ...it 26 174 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 26 Dimensional drawings...
Страница 198: ...INTENTIONALLY LEFT BLANK 26 180 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 26 Dimensional drawings...
Страница 204: ...INTENTIONALLY LEFT BLANK 27 186 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 27 Application examples...
Страница 323: ...INTENTIONALLY LEFT BLANK 36 Publ No 1558550 Rev a557 ENGLISH EN October 7 2011 305 36 Emissivity tables...
Страница 325: ......