Archive for Solids & Liquids

Emissivity of Human Skin in the Waveband between 2 & 6 micrometers

From a Nature Article of the same title:

By DAVID J. WATMOUGH & R. OLIVER, Department of Radiation Physics, Churchill Hospital, Oxford.
Citation: Nature 219, 622 – 624 (10 August 1968); doi:10.1038

Abstract:

The emissivity of human skin epsilon(lambda) in the range 2micro to 6micro has recently assumed considerable importance because of the increasing medical use of infrared scanners to measure skin temperature (t). Several commercially available scanners utilize indium antimonide detectors which are sensitive in the range 2micro to 5.4micro . Such machines measure the energy (Q) Bactrim radiated by the skin and, being calibrated against a standard black body, changes in Q are represented as variations in skin temperature. Dreyfus1 has shown that Q is related to t by an equation of the form, where k is a constant, and where the index n depends on lambda as lambdamax being the wavelength corresponding to the maximum in the emission curve. The importance of variations in emissivity can be seen by differentiating equation (1) for constant Q. We obtain which simplifies to give for Deltat For a skin temperature of 27° C (t=300° K), n is about 12.5. It follows from equation (2) that if epsilon(lambda) were to vary by as much as 5 per cent over the skin surface, this would be interpreted by the scanner as a temperature variation of about 1° C. A fairly accurate knowledge of epsilon(lambda) is thus necessary, for hot spots with temperature elevations of only 2° C are considered to be of clinical significance.

» Read more..

Determination of the Infrared Emissivity with Multi-spectral Thermal Infrared Data from Space

A 2004 Amercian Geophysical Union Conference Presentation by:

Schmugge, T (schmugge@hydrolab.arsusda.gov) , USDA/ARS Hydrology and Remote Sensing Lab, Bldg. 007 – BARC West, Beltsville, MD 20705 United States
Ogawa, K (k-ogawa@dsg.hitachi.co.jp) , Hitachi Ltd., 4-6 Kanda-Surugadai Chiyoda- Ku,, Tokyo, 101-8010 Japan
Ogawa, K (k-ogawa@dsg.hitachi.co.jp) , Faculty of Engineering,University of Tokyo, University of Tokyo, Tokyo, 113-0033 Japan
Rokugawa, S (rokugawa@gpl.t.u-tokyo.ac.jp) , Faculty of Engineering,University of Tokyo, University of Tokyo, Tokyo, 113-0033 Japan » Read more..

Fluke Calibrator Video

Emissivity makes a temperature difference for infrared thermometers.

In the YouTube video below, Frank Liebman, an engineer with Fluke Corporation’s Hart Scientific Division demonstrates the impact that surface emissivity has on temperature measurement and temperature calibration using a modified Fluke blackbody calibrator and Fluke Thermal Imager.

We were surprised to see that no one commented on this video, despite an ending that leaves one hanging, at least us, with the obvious question: How do you do a radiometric calibration of a surface of unknown emissivity using a Fluke Blackbody Calibrator?

Do you have any ideas?

What The Heck is Emissivity? (Part 2)

Fill up two soda cans with hot water and wrap Flagyl ER one in scotch tape. Which one will cool down faster? Obvious, right?

Check it out, you might be surprised!

From the ITC Channel at YouTube.com

Measurement of the surface emissivity of turbid waters

Chinese Journal of Oceanology and Limnology, Volume 5, Number 4, 363-369, DOI: 10.1007/BF02843818

“Measurement of the surface emissivity of turbid waters”, Liu Wenyao, R. T. Field, R. G. Gantt and V. Klemas

http://www.springerlink.com/content/8102732046620458/

Abstract
For interpreting thermal IR imagery of the ocean surface, the emissivity of the sea surface is usually assumed to be constant, approximately 0.98. However, the emissivity varies with the roughness of the sea surface, and the concentration and type of suspended particulates.

The emissivity variations caused by the suspended sediments introduce significant errors in the satellite-derived temperature maps of turbid coastal waters. » Read more..