LumaSense Technologies MC320 Manual - Manual (Page 24)

24 Principle of Thermal Imaging MC320 Thermal Imager Manual
1. By means of a printed table
Various books and literature carry physical constants
tables, but if the measuring condition is not identical, the
constants may not usable. In such cases the literature
should be used only for reference.
2. Determination by ratio — Option 1
A contact-type thermometer is used to confirm that the
measured object is in thermal equilibrium and that the
blackbody-type source is at the same temperature. The
object and the blackbody-type source are then measured
with the radiation thermometer and the resulting energy
ratio is then used to define the emissivity as follows:
Where, EK : ES = 1 : X
3. Determination by ratio — Option 2
An object, resembling a blackbody, is attached to a heat
source to make the temperature of the blackbody part
and the measuring object the same. The ratio of infrared
radiation energies are then determined as in #2 above.
4. Comparison with blackbody surface — Option 1
A very small hole is made in the measured object to
satisfy the aforementioned blackbody conditions, and to
make the temperature of the entire object uniform. Then,
using the emissivity correcting function of thermal
imager, the emissivity is reduced until the temperature of
the point to be measured equals the temperature of the
small hole measured at an emissivity of 1. The emissivity
setting should be the emissivity of the object. (This
applies only when the conditions are the same as at
measurement.)
5. Comparison with blackbody surface — Option 2
If a small hole cannot be made in the object, then the
emissivity can be obtained by applying black paint to the
object and reaching a thermal equilibrium through
similar procedures. But since the painted object will not
provide a complete blackbody, the emissivity of the
painted object needs to be set first and then the
temperature can be measured. The following figure
shows examples of blackbody paint.
EK : energy of blackbody-type source
ES: energy of measured object
X: emissivity of measured object