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Exact spectral emissivity measurements for radiation thermometry (IR thermometry)

Modern emissivity measuring facility for industry-orientated calibrations developed at PTB

This news release is available in German.
spectral emissivity sampleCAPTION: Local variation of the directed spectral emissivity of a car paint sample at a wavelength of 4 µm, measured using a thermography camera. (IMAGE COURTESY PTB)
Industry and research are increasingly relying on non-contact temperature measurements with the aid of heat radiation, for example, for the reliable and reproducible drying of car paint.

In order to attain exact and reliable results, the emissivity of the measured surface has to be known. It can only be determined precisely in complex measuring facilities.

The Physikalisch-Technische Bundesanstalt (PTB) has developed a modern emissivity measuring facility for industry-oriented calibrations.
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ET10 Reflectometer Measures Emissivity

San Diego CA, USA –Surface Optics’ ET10 measures emissivity values in two most commonly used spectral regions, 3 to 5 and 8 to 12 microns.

Its main application is to produce emissivity values for the infrared cameras.

Advanced IR cameras require the input of an emissivity value for accurate temperature calculations. The emissivity values obtained from tables can be far from real leading to large temperature uncertainties.

The ET10 can be used in the lab or in the field and on small or large objects. With the ET10 one can measure emissivity of any surface in just a few seconds.

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Real Time Emissivity Measurement For IR Temp Measurements

Pyrolaser infrared thermometer high temperature measurement sensorThis online page at The Pyrometer Instrument Company website, discusses the emissivity correction techniques employed in their products, the very narrow waveband devices called the Pyrolaser® (Shown here), the Pyrofiber® & the Optitherm® III Emissivity Technology.

(Notes: 1. The article speaks about “emissivity” but the spectral emissivity is implied due to the fact that these devices operate in very narrow wavebands at 865nm, 905nm or 1550nm, according to the model.
2. The article also provides a calculation and describes the radiant power of the laser as “energy”.)

Here’s an edited quote from the page:
“The emissivity is measured by firing a pulsed laser of monitored output energy to the target and measuring the reflected laser energy. Assuming that no energy is transmitted through the target (opaque material) the impinging energy must either be absorbed or reflected.

“The unknown absorbed energy can be calculated from the two measured quantities outgoing energy and reflected energy.

“Since absorptivity and emissivity are equal…the target emissivity (e) is known as soon as the absorptivity is known.

The temperature is measured by collecting the radiance in a narrow band (10-50nm) at the same wavelength (865nm, 905nm or 1550nm depending on the specific instrument) where emissivity is measured with the laser.”

AZ Technology Optical Properties Instrumentation

AZ Technology is an industry leader in measuring the Optical Properties of materials.

All measurements are made with the finest instruments on the market. AZ Technology specializes in the measurement of solar absorption,emittance, reflectance, and transmittance.

Optical properties measurements are made with the following instruments:

The SpectraFIRE measures near normal reflectance directly and the emittance is calculated from the reflectance measurements. SpectraFIRE has the following specification:

32 wave numbers (cm-1); selectable down to 4 cm-1.

Reflectance Repeatability:
2.5 – 16um± 1%
16 – 25um± 1.5%
25 – 40um± 2%

Spectral Resolution:
2.5 to > 40um

The LPSR 200IR measures total hemispherical spectral reflectance directly and solar absorption, transmittance, or emittance is calculated from the reflectance measurements.The LPSR 200IR has the following specification:

250 to 2800nm

Spectral Resolution with Automatic Slit Control:
250-2500nm better than 5% of wavelength
2500-2800nm better than 8% of wavelength

250 to 2500nm±1%
2500 to 2800nm – ±2%

AZ Technology Corporation
7047 Old Madison Pike, Suite 300
Huntsville, AL 35806 USA

Tel: +1 256.837.9877

FAX: +1 256.837.1155