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ManualsBrandsFLUKE CALIBRATION ManualsTest Equipment9133-256 Calibrator Temperature Calibrated to Manufacturer's standards (with certificate)

Application Note

Infrared Temperature

Calibration 101

Using the right tool means better

work and more productivity

hot,” such as the red glow of

the embers of a fire, the yellow

glow of a candle, and the white

glow of an incandescent light

bulb. The color we perceive is

related to the temperature of

the heated object. In fact, steel

workers claim that they can

accurately judge the tempera-

ture of molten steel to within

50 °C based on the color alone.

Like the eyes of steel work-

ers, infrared thermometers are

also designed to be sensitive

around a specific band of

wavelengths. The most

commonly used spectral band

for general purpose infrared

thermometers is from 8 µm to

14 µm (8 to 14 micrometers).

Infrared radiation is elec-

tromagnetic radiation with

wavelengths longer than visible

light and shorter than millime-

ter wave radiation. Terms like

wavelength and amplitude are

used to describe infrared and

other forms of electromagnetic

radiation. For example, wave

amplitude describes the inten-

sity of electromagnetic radiation

and wavelength is used among

other things to determine

whether it is a microwave, visi-

ble light, or infrared radiation.

Infrared thermometers let you measure a target’s

surface temperature from a distance without physically

touching it. To point and shoot at a target to measure

its temperature may seem a little like magic. This

application note demysties the process of infrared (or

“IR”) thermometry and explains why regular calibration

is important for maximizing the value of these useful

devices.

From the Fluke Digital Library @ www.fluke.com/library

How infrared

thermometers

measure temperature

Infrared thermometers

measure the electromagnetic

radiation emitted by an object

as a result of the object’s

temperature. Until an object

becomes very hot, most of this

radiation is in a band of wave-

lengths called the infrared

spectrum. Very hot objects emit

visible light which is also a form

of electromagnetic radiation.

While the human eye is very

sensitive to yellow light with

wavelengths around 0.555

micrometers, it cannot detect

light with wavelengths longer

than 0.700 micrometers (red)

and shorter than the 0.400

micrometers (violet). Although

our eyes can’t detect the energy

outside of this narrow band of

wavelengths, called the visible

spectrum, we still know it is

there, because we can detect it

with a radiometer.

“Seeing” temperature

We have some experience

measuring temperature by

detecting electromagnetic

radiation with our eyes. We are

familiar with things that “glow

How small is a micrometer?

A micrometer is very small; in

fact, it is one one-millionth of a

meter. To put that into perspective,

around 100 micrometers would

equal the thickness of a human

hair.

Summary of content (7 pages)

PAGE 1
Infrared Temperature Calibration 101 Using the right tool means better work and more productivity Application Note Infrared thermometers let you measure a target’s surface temperature from a distance without physically touching it. To point and shoot at a target to measure its temperature may seem a little like magic. This application note demystifies the process of infrared (or “IR”) thermometry and explains why regular calibration is important for maximizing the value of these useful devices.
PAGE 2
Calibration is easy with the 4180 Series Precision Infrared Calibrator. Temperature source In spite of our experiences with seeing temperature, confidence in IR temperature measurement usually requires the use of calibrated instruments.
PAGE 3
same temperature. Emissivity is greatly affected by the type of material and surface finish of an object. Metals with smooth surface finishes tend to have low emissivity and high reflectivity while long narrow holes have relatively high emissivity and very little reflectivity. The sum of emissivity, reflectivity, and transmission is always equal to one.
PAGE 4
resistance thermometer (PRT) physically into the target. This technique also neglects temperature losses at the surface of the infrared target. With this type of calibration, the user may not be aware that complicated emissivity-related corrections are required at each temperature in order to achieve the accuracy claimed by the manufacturer.
PAGE 5
Manufacturer recommended large target IR thermometer spot size 199.3 Smaller target = IR thermometer field of view Peripheral vision in infrared thermometers makes large targets necessary for many calibrations. the object appears to glow. The emissivity at each wavelength, called spectral emissivity, determines how bright each wave will be. The thermometer uses the total brightness of a selected band of these waves to determine the temperature.
PAGE 6
the correct temperature. This is because the reflected energy is a relatively large proportion of the signal received by the thermometer when the target temperature is below ambient temperature. This situation is often referred to as a low signal-to-noise ratio. IR thermometers measure a group of wavelengths called a spectral band.
PAGE 7
sometimes called a non-contact thermometer because of its ability to measure the temperature of a surface without making contact with that surface. Infrared radiation: Infrared (IR) radiation is electromagnetic 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.