5. Emissivity Selection mode—Pressing the Mode button five
times with the IRT powered on causes the Greek letter to
appear blinking on the top line of the display. Unlike in other
modes, the blinking icon indicates that a new mode has
already been entered—in this case, Emissivity Selection
mode.
The factory-set default emissivity value of the IRT105 is 0.95.
To enter the emissivity value of your target surface material:
• Locate the material in Table 1 in the shaded box,
Accounting for Emissivity.
• Press the Meas. (measure) button as many times as
necessary to change the display from the factory-set
default value of 0.95 to the desired value. Note that each
press of the button increases the displayed value by 0.01.
After five presses, starting at 0.95, the displayed value will
be 1.00. The next press will change the value to 0.10—the
lowest possible emissivity setting. Each subsequent press
of the Meas. (measure) button will increase the value by
0.01 units.
• When you have reached the desired emissivity value, press
the Mode button to store the setting. The IRT105 will use this
value in its temperature calculations until you change it.
ACCOUNTING FOR EMISSIVITY
Emissivity is the ability of an object to reflect or absorb
IR radiation (energy). Because the IRT105 measures the
amount of infrared energy emitted by a surface, the IRT’s
measurements are most accurate when they take into
account the characteristic emissivity of the target material.
A perfectly absorbent surface (called a black body) has an
emissivity (represented by the Greek letter
) of 1; it
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