46
Rev
001
7.16 What is emissivity?
The amount of infrared radiation emitted by a surface depends on both its
temperature and its emissivity. Surfaces that are good reflectors (e.g. polished
metal) are poor emitters, and surfaces that are good emitters (e.g. human skin)
are poor reflectors. A
black body
is defined as an object that absorbs all
radiation falling on it; and it is a perfect emitter of radiation.
The
emissivity
of a surface (usually written
ε
) is the ratio of energy radiated by
that surface to energy radiated by a
black body
at the same temperature. For
accurate temperature measurements, the emissivity of the surface being
measured must be entered into the camera. This is done by entering a number
in the range 0.10 (for polished chromium) to 1.00 (for a black body). An
emissivity lookup table is provided, which lists the emissivities of a range of
common materials.
It is not recommended that temperature measurements be attempted when
emissivity values lower than 0.70 are required, because large errors are likely
due to reflected radiation from surrounding objects.
How do I set emissivity?
1. Press Hotkey 4
to select the menu (Fig 1).
2. “Infrared Settings”
.will be highlighted. Press Hotkey 3
to select it.
3. Emissivity is the first item in the “Infrared Settings” menu, and will be
highlighted. See Fig 2.
4. Use the left/right navigation buttons
to change the emissivity value.
5. Or select the emissivity table by pressing Hotkey 3
, and use the
up/down navigation buttons
to highlight the desired value/surface.
6. Press Hotkey 4
to exit.
Fig 2.
Hotkey 1 Hotkey 2 Hotkey 3 Hotkey 4
Fig 1.
Centre toggle button
Up/Down, Left/Right
navigation buttons.
