Applications Guide
Modline 5
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The window material must be highly transparent in the Sensor's infrared spectral region. Yet, there is
always some signal loss due to reflection or absorption when using a window. To compensate for this
loss, first multiply the emissivity of the target object by the window's transmission factor (T) shown in
the Window Selection Guide. Then adjust the emissivity setting to this value.
Example:
Emissivity of object = 0.8
Transmission factor of window = 0.92
Emissivity setting = 0.8 X 0.92 = 0.74
The window specifications given at the top of the chart are suitable for most applications. However,
high pressure or vacuum chamber applications may require windows that are thicker than 1/8" (3 mm).
Be aware that transmission of thicker windows may be significantly degraded.
It is good practice to use a window at least twice the diameter of the Cone of Vision at the point where
the window is to be installed. Note that the dimensions of the Cone of Vision can be changed by focusing
the optics. It is essential for all Sensor Series except Series 5R that you never allow any part of the Cone
of Vision to be obstructed.
illustrates the correct use of windows. Keep the window clean to
prevent low temperature indications.
Figure 90: Viewing a Target through a Sight Hole and Window
8.10.1
Special Considerations for Ratio Units
Because Modline Series 5R ratio Sensors compare the radiation detected at two separate wavelengths,
the best windows for these units have the same transmission value at both wavelengths. All acceptable
Series 5R windows specified in the Guide have this characteristic. No additional E Slope adjustment is
required when these windows are used.
Note that certain materials, which are transparent to the human eye, can cause serious measurement
errors when with a 5R Ratio Sensor. For instance, it almost always causes problems if any of soda-lime
plate glass, "PLEXIGLASTM", water, or "PYREXTM" glass lies between the Sensor and the target during
a measurement. Similarly, if you need to reflect your target's radiation in order to measure it with a 5R
Ratio Sensor, use a front surface gold mirror, not a mirror with an aluminum reflecting surface.
The materials listed in the Guide are not all common optical materials and you may have some difficulty
locating a source for windows. If you do, here are some suggestions.
Sensor Lens
Window
Sight Hole
Cone of Vision
Target
