Information

7 Fluke Corporation Infrared Temperature Calibration 101
sometimes called a non-contact
thermometer because of its abil-
ity to measure the temperature
of a surface without making
contact with that surface.
Infrared radiation:
Infrared (IR) radiation is elec-
tromagnetic radiation with
wavelengths longer than visible
light and shorter than millimeter
wave radiation. All surfaces with
temperatures above absolute
zero (-273.15 °C) emit infrared
radiation.
Opaque:
An opaque object does not allow
electromagnetic radiation to
pass through it. A surface may
be opaque for some wave-
lengths and transparent for
others. For example, glass is
opaque to infrared radiation
with wavelengths longer than
~3 microns but is transparent to
visible light.
Radiance:
A measure of the intensity of
electromagnetic radiation emit-
ted by or passing through a
particular area in a specified
direction. It is defined as power
per unit area per unit solid
angle. The SI unit of radiance is
watts per steradian per square
meter (W·sr
--1
·m
-2
).
Radiometric calibration:
A calibration that compares
the measurements made by an
instrument to the measurements
made by a reference radiometer,
for the purpose of detecting
and reporting, or eliminating by
adjustment, errors in the instru-
ment tested.
Radiometer:
A device used to measure the
power, also called radiant flux,
in electromagnetic radiation.
See also infrared thermometer.
Reflection:
Electromagnetic radiation is
reflected when it changes direc-
tions at a surface while remain-
ing in the first medium without
passing into the second.
Reflectivity:
The fraction of incident radia-
tion reflected by a surface.
Scatter:
An effect caused by non-unifor-
mities in a medium that forces
light to travel in a direction that
deviates from a straight path.
Spectral band:
A well-defined, continuous
wavelength range electromag-
netic energy. The range from
8 to 14 microns used by many
infrared thermometers is an
example of a spectral band.
Spectral radiance:
A measure of the intensity of
electromagnetic radiation at a
specific wavelength emitted by
or passing through a particular
area in a specified direction. It
is defined as radiance per unit
wavelength. Spectral radiance
has SI units W·sr
--1
·m
-3
when
measured per unit wavelength.
Spot size:
The diameter of the measure-
ment spot of a radiometer. It is
usually defined as the diameter
that collects a defined percent-
age of the total power collected
by the radiometer, e.g., 95 %.
This spot size will vary with
distance from the radiometer.
Thermodynamic temperature:
A temperature value based on a
scale that is consistent with all
the known laws of thermody-
namics.
Transmission:
The process by which some
fraction of electromagnetic
energy reaching a surface is
allowed to pass through the
material belonging to that
surface. Transmission assumed
to be zero for surfaces that are
opaque at the measured
spectral band.
Transmissivity:
A measure of how much of an
electromagnetic wave passes
through a surface. It is calcu-
lated by taking the ratio of the
value that passes through the
surface to the value that reaches
the surface.
Uniformity:
A uniformity specification is an
expression of the maximum
allowable difference between
two measurement results
within the region contained
by a measurement medium or
surface.
Wavelength:
The distance in the direction
of a moving wave that it takes
to complete a single cycle. In a
wave, a property such as elec-
tric potential varies cyclically
with position. In a moving wave
the position also changes with
time.
Fluke Calibration
PO Box 9090,
Everett, WA 98206 U.S.A.
Fluke Europe B.V.
PO Box 1186, 5602 BD
Eindhoven, The Netherlands
For more information call:
In the U.S.A. [phone] or Fax [phone]
In Europe/M-East/Africa [phone] or Fax [phone]
In Canada (800)-36-FLUKE or Fax [phone]
From other countries [phone] or Fax [phone]
Web access: http://www.fluke.com
©2007-2011 Fluke Corporation. Specifications subject to change without notice.
Printed in U.S.A. 1/2011 3187781C A-EN-N Pub_ID: 11329-eng, rev 03
Modification of this document is not permitted without written permission from Fluke Corporation.
Fluke Calibration. Precision, performance, confidence.
™