Measurement apparatus and procedure for the determination of surface emissivities
First Claim
1. A method of determining the electromagnetic surface emissivity of a radiating material, independently of any other surface losses and in accordance with theoretical data derived for an ideal system free from all uncorrelated radiation, comprises the steps of:
- providing a connected system that is closed with respect to all uncorrelated radiation sources outside the system and capable of stabilizing uncorrelated radiation within the system;
isolating said radiating material under test in a preselected chamber in a test section maintained within the system;
maintaining said material and the system in a humid-free state;
isothermally stabilizing the material in the system;
heating the material from a first point in time to a second point in time;
measuring the physical temperature of the heated material at said first and second points in time;
measuring the radiation energy emitted by the heated material in terms of brightness temperature at said first and second points in time and using the difference in radiation energy in terms of brightness temperature between said first and second points in time divided by the difference in the physical temperature of the heated material between said first and said second points in time as being indicative of the electromagnetic surface emissivity of the heated material.
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Abstract
The invention embodies a system and procedure for independently determining the surface emissivity of a mesh membrane material 12. The system is a closed one with respect to unwanted or uncorrected radiation outside the system and is composed of a radiometer 11 connected to a horn antenna 13, a test section 15 sealed to the horn antenna 13 and a cryogenically cooled matched load 17 exposed to the interior of the system. The material 12 is enclosed in a convection test chamber 14 within test section 15, heated within test chamber 14 and allowed to radiate within the system such that a component of the radiation energy of material 12 is measured by the radiometer 11 in terms of brightness temperature. The matched load 17 serves as the stabilizing source of uncorrelated radiation within the system by radiating within the system at a constant cryogenic temperature. The actual physical temperature of the material 12 is also measured during the heating process. The difference in brightness temperature over a selected period of time when divided by the physical temperature over the same period of time is the emissivity of the material 12 according to a derivation of the Raleigh-Jeans approximation for an ideal system free from all uncorrelated radiation.
37 Citations
18 Claims
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1. A method of determining the electromagnetic surface emissivity of a radiating material, independently of any other surface losses and in accordance with theoretical data derived for an ideal system free from all uncorrelated radiation, comprises the steps of:
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providing a connected system that is closed with respect to all uncorrelated radiation sources outside the system and capable of stabilizing uncorrelated radiation within the system; isolating said radiating material under test in a preselected chamber in a test section maintained within the system; maintaining said material and the system in a humid-free state; isothermally stabilizing the material in the system; heating the material from a first point in time to a second point in time; measuring the physical temperature of the heated material at said first and second points in time; measuring the radiation energy emitted by the heated material in terms of brightness temperature at said first and second points in time and using the difference in radiation energy in terms of brightness temperature between said first and second points in time divided by the difference in the physical temperature of the heated material between said first and said second points in time as being indicative of the electromagnetic surface emissivity of the heated material. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An apparatus for determining the electromagnetic surface emissivity of a test material independent of all other surface losses comprising:
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a radiation energy receiving means for receiving electromagnetic radiation in the form of brightness temperature emitted by said test material upon heating; a test section housing the test in a preselected chamber material and connected to said radiation energy receiving means; a means, on said test section, for heating the test material from a first point in time to a second point in time whereby the test material emits electromagnetic radiation; a means for measuring the physical temperature of the test material; a means for connecting said radiation energy receiving means to said test section; an uncorrelated radiation stabilizing means connected to said test section; a recording means for indicating the brightness temperature and the physical temperature of the test material; and a computing means for determining the electromagnetic emissivity of said test material from the brightness temperature and the physical temperature of the test material at the first and second points in time. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification