Setting Emissivity And Reflected Temperature Coefficient (Rtc) - RIDGID RT-3 Manuel D'utilisation

RT-3, RT-5x, RT-7x and RT-9x Thermal Imagers
Setting Emissivity And Reflected
Temperature Coefficient (RTC)
Emissivity
Emissivity is a term use to describe energy emit-
ting characteristics of materials and has a value
ranging from 0 to 1. Emissivity values approaching
zero are typical for things with a high reflectivity,
like a mirror. Low reflectivity materials (such as
items painted flat black) have emissivity values
approaching 1. Emissivity is material-specific and
must be adjusted for correct measurement re-
sults. Improper emissivity values can cause sig-
nificant temperature errors.
Non-metals (paper, ceramic, gypsum, wood,
paints and coatings), plastics and food typically
have high emissivity, which means that the sur-
face temperature can be easily measured using
infrared.
Because of their low or non-uniform emissivity,
bright metals and metal oxides only have limited
suitability for infrared measurement. Highly inac-
curate measurements should be expected. A
remedy for this is coatings that increase emissiv-
ity, e.g. paint or emission adhesive, which must
be applied to the object to be measured.
Alternately, the RT-5x, RT-7x and RT-9x thermal
imagers are equipped with -Assist, a feature that
will determine the emissivity using the -marker
affixed to the target surface.
The following tables gives the standard prepro-
grammed materials and emissivity and typical
emissivity of common materials for use as a
guideline in setting emissivity.
Standard Preprogrammed Materials
Material (material temperature)
Aluminum, bright rolled (170°C)
Cotton (20°C)
Concrete (25°C)
Ice, smooth (0°C)
Iron, emery-ground (20°C)
Iron with casting skin (100°C)
Iron with rolling skin (20°C)
Gypsum (20°C)
Glass (90°C)
Rubber, hard (23°C)
Rubber, soft grey (23°C)
Wood (70°C)
Cork (20°C)
12
Other Common Materials
Material (material temperature)
Radiator, black anodized (50°C)
Copper, slightly tarnished (20°C)
Plastics: PE, PP, PVC (20°C)
Steel, heat-treated surface (200°C)
Brick, mortar, plaster (20°C)
Selecting/Setting The Emissivity
1. Select the Emissivity function.
2. Move the joystick up/down to select the de-
sired material (with permanently set emissiv-
ity) and then press OK.
3. Move the joystick up/down until User defined
is selected. Move the joystick to the right until
desired emissivity value is selected. Manually
set value and press OK.
Reflected Temperature Coefficient (RTC)
Information:
The Reflected Temperature Coefficient (RTC) is
calculated based on the Reflected Temperature.
In most cases, the reflected temperature is iden-
tical to the ambient air temperature. Only when
objects with strong emissions at much lower tem-
peratures (such as cloudless skies during outdoor
readings) or much higher temperatures (such as
ovens or machines) are in proximity to the object
being measured should the radiation temperature
of these sources be determined and used. The
Emissivity
reflected temperature has little effect on objects
0.04
with high emissivity.
0.77
0.93
Reflected temperature can be determined by:
0.97
1. Use a 12" x 12" (300 mm x 300 mm) minimum
0.24
sheet of aluminum foil. Crumple up the alu-
0.80
minum foil.
0.77
0.90
2. Uncrumple the aluminum foil. Attach the foil to
0.94
cardboard the same size.
0.94
3. Place the foil directly in front of the surface that
0.89
you want to measure the temperature of, foil
0.94
side out.
0.70
4. Set the thermal imager emissivity to 1.0.
5. Use the thermal imager to measure the
temperature of the middle of the foil. Use
Copper, oxidized (130°C)
Brass, oxidized (200°C)
Paper (20°C)
Porcelain (20°C)
Flat Black paint (80°C)
Steel, oxidized (200°C)
Clay, burnt (70°C)
Transformer paint (70°C)
Emissivity
0.98
0.04
0.76
0.94
0.61
0.97
0.92
0.97
0.52
0.79
0.91
0.94
0.93
999-995-119.10_REV. A