FLIR E50 User Manual

Theory of thermography
32
Figure 32.5 Wilhelm Wien (1864–1928)
The sun (approx. 6 000 K) emits yellow light, peaking at about 0.5 μm in the middle of
the visible light spectrum.
At room temperature (300 K) the peak of radiant emittance lies at 9.7 μm, in the far infra-
red, while at the temperature of liquid nitrogen (77 K) the maximum of the almost insignif-
icant amount of radiant emittance occurs at 38 μm, in the extreme infrared wavelengths.
Figure 32.6 Planckian curves plotted on semi-log scales from 100 K to 1000 K. The dotted line represents
the locus of maximum radiant emittance at each temperature as described by Wien's displacement law. 1:
Spectral radiant emittance (W/cm
2
(μm)); 2: Wavelength (μm).
32.3.3 Stefan-Boltzmann's law
By integrating Planck’s formula from λ = 0 to λ = ∞, we obtain the total radiant emittance
(W
b
) of a blackbody:
This is the Stefan-Boltzmann formula (after Josef Stefan, 1835–1893, and Ludwig Boltz-
mann, 1844–1906), which states that the total emissive power of a blackbody is propor-
tional to the fourth power of its absolute temperature. Graphically, W
b
represents the
area below the Planck curve for a particular temperature. It can be shown that the radiant
emittance in the interval λ = 0 to λ
max
is only 25% of the total, which represents about the
amount of the sun’s radiation which lies inside the visible light spectrum.
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FLIR E50 Specifications

General

Resolution	240 x 180 pixels
Image Storage	SD card
Focus	Manual
Image Frequency	60 Hz
Accuracy	±2°C or ±2% of reading
Digital Camera	3.1 MP
Digital Zoom	4x continuous
Measurement Presets	Yes
Laser Pointer	Yes
Battery Operating Time	4 hours
Spectral Range	7.5 – 13 µm
Operating Temperature Range	-15°C to +50°C
Storage Temperature Range	-40°C to +70°C
Thermal Sensitivity	<0.05°C at 30°C
Field of View	25° × 19°
Temperature Range	-20°C to +650°C
Display	3.5" LCD touchscreen
Image Modes	Thermal, MSX
Battery Type	Li-Ion battery
Weight	0.825 kg