Apogee SI-421 Kullanıcı El Kitabı - Sayfa 15
Ölçüm Cihazları Apogee SI-421 için çevrimiçi göz atın veya pdf Kullanıcı El Kitabı indirin. Apogee SI-421 20 sayfaları. Infrared radiometer
Ayrıca Apogee SI-421 için: Kullanıcı El Kitabı (20 sayfalar), Kullanıcı El Kitabı (20 sayfalar)
2
b
=
C
2
⋅
T
+
1 C
D
Where C2, C1, and C0 are the custom calibration coefficients listed on the calibration certificate (shown
above) that comes with each SI-100 series radiometer (there are two sets of polynomial coefficients, one
set for m and one set for b). Note that T
temperature in K minus 273.15) before m and b are plotted versus T
To make measurements of target temperatures, Eq. (1) is rearranged to solve for T
of S
and T
are input, and predicted values of m and b are input:
D
D
(
4
T
=
T
+
m
⋅
T
D
Emissivity Correction:
Appropriate correction for surface emissivity is required for accurate surface temperature measurements.
The simple (and commonly made) emissivity correction, dividing measured temperature by surface
emissivity, is incorrect because it does not account for reflected infrared radiation.
The radiation detected by an infrared radiometer includes two components: 1. radiation directly emitted
by the target surface, and 2. reflected radiation from the background. The second component is often
neglected. The magnitude of the two components in the total radiation detected by the radiometer is
estimated using the emissivity (ε) and reflectivity (1 - ε) of the target surface:
E
=
⋅ ε
E
Sensor
T
arg
where E
is radiance [W m
Sensor
the target surface, E
Background
outdoors the background is generally the sky), and ε is the ratio of non-blackbody radiation emission
(actual radiation emission) to blackbody radiation emission at the same temperature (theoretical
maximum for radiation emission). Unless the target surface is a blackbody (ε = 1; emits and absorbs the
theoretical maximum amount of energy based on temperature), E
reflected radiation from the background.
Since temperature, rather than energy, is the desired quantity, Eq. (1) can be written in terms of
temperature using the Stefan-Boltzmann Law, E = σT
fourth power of its absolute temperature):
4
⋅ σ
T
=
⋅ ε
⋅ σ
Sensor
where T
[K] is temperature measured by the infrared radiometer (brightness temperature), T
Sensor
actual temperature of the target surface, T
(usually the sky), and σ is the Stefan-Boltzmann constant (5.67 x 10
temperatures in Eq. (2) is valid for the entire blackbody spectrum.
⋅
T
+
C
0
(3)
D
is converted from Kelvin to Celsius (temperature in C equals
D
)
1
S
+
b
−
273
.
15
(4)
4
D
(
)
+
1
−
ε
⋅
E
et
Background
sr
] detected by the radiometer, E
-2
-1
is radiance [W m
(
)
4
T
+
1
−
ε
⋅
⋅ σ
T
T
arg
et
Background
Background
(1)
Target
sr
] emitted by the background (when the target surface is
-2
-1
sensor
4
(relates energy being emitted by an object to the
4
(2)
[K] is brightness temperature of the background
-8
.
D
[C], measured values
T
is radiance [W m
sr
-2
will include a fraction (1 – ε) of
W m
-2
K
-4
). The power of 4 on the
15
] emitted by
-1
[K] is
Target