Menu Item "Difference - InfraTec VARIOCAM HD User Manual

The factory setting of the emissivity is 1.00. Therefore, it is assumed that 100 % of the
measured radiation is emitted by the measuring object. The measuring object corresponds to
the "ideal black-body emitter" and is non-reflective.
If the actual (lower) emissivity of the measuring object is to be taken into consideration, it is absolutely
necessary to also determine the ambient temperature ("reflected temperature"), which must also be
entered as a correction parameter. The ambient temperature frequently differs from the air temperature or
even from the temperature of the camera.
Saving the distance is of particular importance for a number of measuring situations, for example in order
to be able to also perform geometric measurements within the thermograms when analyzing the
thermograms. However, if "manual" is the option selected for setting the distance, the distance input with
the correction parameters is only saved within the thermogram. This is suitable in the event of stationary
measurement setups where the distance between camera and measuring object does not change and
can be determined easily. If the "Automatic" option is selected, the distance calculated from the process
of adjusting the focus is displayed after each manual or automatic focusing ("Dist", see chapter 8.2.1
Elements of the user interface – page 28) and saved within the thermal image. The laser rangefinder*
(LRF) integrated into the VarioCAM
approx. 70 m (see chapter 9.3.8 Menu item "Laser" – page 66). If the "Automatic" option is selected, the
distance measured with the LRF before the image was recorded is saved to the thermal image once the
focus setting is changed afterwards.
Fig. 148 Distance – Manual
The distance entered for the correction parameters does not retroact on the focus.

9.3.5 Menu item "Difference"*

When activating the function "Difference" the temperatures of the previous image content will be
deducted from the temperatures of the current image pixel by pixel. This function can be very helpful if
very small temperature changes should be displayed, but the scene has a larger temperature gradient. If
areas of the scene warm up after activating the function "difference", positive temperatures are displayed.
When cooling down, negative temperatures are displayed. When activating the function "difference" the
difference mode is displayed in the upper right corner of the image above the palette:
the temperature scale °C to the left of date/time disappears. All temperature differences are shown in
Kelvin, independent of the choice of the temperature unit in menu item "System Regional" (see chapter
9.4.2 Menu item "Subframes"* – page 69). The temperature scale setting is being adjusted when
switching in the "difference" mode.
64
® HD allows for precise distance measurement up to a distance of
Fig. 149 Distance – Automatic
© InfraTec GmbH 2016
Thermography System VarioCAM
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® HD