FLIR E40 User Manual

Theory of thermography
32
32.4 Infrared semi-transparent materials
Consider now a non-metallic, semi-transparent body – let us say, in the form of a thick flat
plate of plastic material. When the plate is heated, radiation generated within its volume
must work its way toward the surfaces through the material in which it is partially ab-
sorbed. Moreover, when it arrives at the surface, some of it is reflected back into the inte-
rior. The back-reflected radiation is again partially absorbed, but some of it arrives at the
other surface, through which most of it escapes; part of it is reflected back again.
Although the progressive reflections become weaker and weaker they must all be added
up when the total emittance of the plate is sought. When the resulting geometrical series
is summed, the effective emissivity of a semi-transparent plate is obtained as:
When the plate becomes opaque this formula is reduced to the single formula:
This last relation is a particularly convenient one, because it is often easier to measure
reflectance than to measure emissivity directly.
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FLIR E40 Specifications

General

Resolution	160 x 120 pixels
Accuracy	±2°C or ±2% of reading
Focus	Manual
Image Storage	SD card
Image Frequency	60 Hz
Digital Camera	3.1 MP
Battery operating time	Approx. 4 hours
Operating Temperature	-15°C to +50°C
Storage Temperature	-40°C to +70°C
Spectral Range	7.5 - 13 µm
Field of View	25° x 19°
Display	3.5 in color LCD
Image Modes	Thermal, Visual, MSX
Measurement Presets	Center Spot, Hot Spot, Cold Spot
File format	JPEG
Battery type	Li-Ion battery
Connectivity	USB, Wi-Fi
Thermal Sensitivity	< 0.07°C @ +30°C (+86°F) / 70 mK