Principles behind the TIR100

Principles behind the TIR100

Measuring principle

The sample is subject to thermal radiation at a temperature of 100°C. A black body half-sphere radiator is used to capsulate the sample to ensure homogenous illumination. The reflected infrared radiation is observed at an angle and is converted into a numeric value. This value is then plotted against a calibration table from high and low emissivity reference standards.
All of this is accomplished at a touch of a button when using the TIR.

Specifications of the TIR100-2

Voltage range 90 VAC – 260 VAC
Power rating 240 VAC max. 130 W
120 VAC max. 260 W
Measuring range As Calibration Standards
Measure Uncertainty +- 0,005 (lowE) … +-0,01 (hiE)
Spectral range 2,5 – 40µm
λmax of radiant energy 7,8 µm
Radiator temperature 100°C
Measuring Duration approx. 5 sec.
Measuring spot approx. 5mm
Interface USB-B
Dimension 230mm x 140mm x 120mm
Weight TIR100-2: approx. 2,0kg

Some basic physics principles

Stefan Boltzmann‘s law

The following physic principles are used to determine the emissivity from a black body radiator. 
Every body with a temperature above absolute zero radiates thermal heat. The quantity of heat (power) is given by

P= σ * ε * T4
P = RadiativePower [W/㎡]
ε = Emissivity
σ = Planck’s Constant [W/K4㎡]

Emissivity ε is the degree of radiative energy compared to that of an ideal blackbody: 
ε = 0 .. 1


Wien’s displacement law states that the wavelength distribution of radiated heat energy from a black body at any temperature has essentially the same shape as the distribution at any other temperature, except that each wavelength is displaced, or moved over, on the graph. 

The wavelength of maximum radiative energy could be calculated by


Principles of emissivity measurement

Principles of emissivity measurement1 Conditions
Principles of emissivity measurement2 Spectral measurement
Principles of emissivity measurement3 Integral measurement

Some TIR100 principles

Based on the following principles, the TIR100 can give a numeric value

TIR100 Principles Diagram

Measurement of reflected energy of a 100°C blackbody with hemispherical radiator

Black body power:
Pb = ε x σ x T4 (ε ~ 1)

Reflected power:
Pr = r x Pb

ε = 1 – r

Some mathematical principles

Based on the linear equation below, the TIR100 can calculate an emissivity value of a sample

Emissivity Calculation