US2666089A - Hemispherical radiometer sensing unit - Google Patents

Description

Jan. 12, 1954 J, T. GIER ETAL 2,666,089

HEMISPHERICAL RADIOMETER SENSING UNIT Filed June 1, 1951 9 @1144 f *1 f7; I Y! Z11 INVENTOR5 Patented Jan. 12, 1954 2.666.089 nmvnsprrsmom. lltliliqlilli fififi-TER ISENSING Joseph *r. Gfenfbakland, amiitebertvgnmikie, Lafayette, "califi fassignors to ",Zlhe ne eers r The University "of California, Berkeley, Galif.

Application-J me-1, 1951,Serial No.?229,471

a claims. (or. rat-r) -1 This invention relates to and in generalhas for -its objectjthe-provision of a sensing .unit for 'sensing-t-he totalheat-radiated from'a hemisphere ofsspa'ce (halfspace) at anyvgive'n time. 7, I V

-More specifically, the {object of this invention is the-provision of asensing unit including aflat thermal resistance plate provided on opposite sides thereof respectively with the hot and cold junctionsof a thermopile, the radiation receiving-side of said radiometer being blackened and its opposite side being highly'poli shed and wherein meansiszprovided for subjecting both sides of the'm'eterto a uniform and constant current of air.

'ZGhe invrition possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the following description wherethat form of the invention which has been selected for illustration in the drawings accompa'riyin g and forming apartof the present speciirca-ticn is'outlined in fun. Inf'said drawings, one form of =the-invention-is sliown, buti-t is'to be understood that it is-not limited to such form, ince the invention as set forth in the claims may '11" "nib'oldied' i' n' a plurality" of forms.

R'eferring to 'the drawings:

Fig. 'l is a perspective view of a radiometer sensing unit embodying'thepbje'cts ofour'invention.

Fig. 2 is an enlarged perspective view of the sensing unit with portions thereof broken away to show its thermopile and the thermocouples thereof.

Fig. 3 is a section taken on the line 3-3 of Fig. 2.

The device as shown in the figures includes a base I and an air blower 2 mounted thereon and driven by an electric motor 3. Secured to the discharge end of the blower is a nozzle 4 having a generally rectangular mouth 5, and supported from the nozzle by arms 6 is a sensing unit generally designated by the reference numeral 1.

As shown in Figs. 2 and 3, the sensing unit 'I is of laminated construction and is formed about a relatively thin central rectangular plate 8 made from a thermal resistant material such as a phenol condensation product. Supported on the plate 8 is a thermopile generally designated by the reference numeral 9 having its hot junctions or thermocouples ll disposed on the upper face of the plate 8 and its cold junctions l2 disposed on the lower face -thereof. Conveniently the thermopile can be made;.of alternate sections Qof copper and-constantan wire, the adjacent ends of thesesections being-solderedto .form-theopposed thermocouples ll and i2. Gorihcted series with the thermopilethrough. leads :3 and 1 4 is 'a potentiometer I5.

v Bonded to the centraLplateB: over-.thehotjunctions ll :is an upper thermal resistant plate It. Similarly bonded to the lower face of the .plate 8 is a thermal resistant plate l- 'l. Bonded to the outerfaces of reach of .the plates 16 and l1 respectively are aluminum plates I-8 and IS. The upper face of the plate 18 isblackened by apply- .ing thereto a layerof non-reflecting. black paint It. The lower or exposed face of the lower: aluminum {plate I 9 should "be highly polished so was eifectively to reflect all [radiation to which it may :be subjected. -In addition tozthis, the.plate-can be shielded if desired. ,4 p v .1 Mounted within a. shallow recess formed-in the servingas means for determining the absolute temperature of the sensing unit 1.

7 "From an inspection of Fig. -1,it willbe' noted that the radiometer unit 1 is directalignment with the end of the nozzle 4, and is so positioned that air from the blower will sweep over both faces thereof.

The upper face of the sensing unit 1 is unobstructed and consequently it is in a position to receive radiation from half space or the hemisphere lying above it. It is for this reason that the device in combination with the potentiometer l5 has been designated a hemispherical radiometer. Furthermore, since in this instrument, the use of windows (glass or otherwise) is unnecessary, it is under the influence of the total thermal radiation from one half space rather than only a selected portion thereof, as would be the case if such radiation had to pass through a physical window of some sort.

The blower produces uniform and constant convection eflects' upon both the upper and lower surfaces of the sensing unit and as a result approximately one half of the net radiation absorbed by the black upper surface of the meter flows through the meter, thereby producing a Kzthe calibration constant of the meter, 'v the E. M. F. of thethermopile azstefan-Bolzmann constant, and

Tm=the absolute temperature of the radiometer By blackening the lower face of plate I9 to' correspond with the blackened upper face of the plate 18, the radiometer will then serve to meas- 1 ure the net exchange by radiation across the plane of the meter, this being proportional to the electromotive force developed by the ther mopile.

From the above description it will benoted that we have provided a simple but effective hemispherical radiometer sensing unit which, by a suitable choice of the blackening material, can be made to respond equally to all wavelengths of radiation in the thermal radiation band. Since the receiving surface of the instrument is a plane, it sees a whole hemisphere, and'a single reading gives directly the summation of the energy falling on the plane of the meter surface from all directions. The absorptivity of the meter is independent of the angle of incidence for the cosine law is obeyed. Due to the low thermal resistance and capacity of the meter, the response time is small. As previously indicated, the blower serves to maintain uniform convection losses from both surfaces of the radiometer unit independent of the air currents and wind prevailing at the location of the meter, and also tends to decrease the response time by maintaining a high rate of heat transfer from the meter. This in turn helps to maintain uniform, reproducible readings and to prevent the temperature of meter from rising substantially above the ambient air temperature.

Having thus described our invention, what we claim and desire to secure by Letters Patent is:

1. A radiometer sensing unit comprising. 9. thermal resistance element; a thermopile mounted on said thermal resistance element with its hot and cold junctions disposed on opposite sides thereof; a black body disposed over said 4 hot junctions and a body having an outer polished surface disposed over said cold junctions; and means for passing a gaseous current over said black body and said polished surface, the upper face of said sensing unit being unobstructed so as to enable it to see the total hemisphere.

2. A radiometer sensing unit comprising: a base; a blower mounted on said base and including an elongated nozzle; a relatively flat thermal resistance element mounted in alignment with said nozzle; a thermopile mounted on said thermal resistance element with its hot and cold junctions disposed on opposite sides thereof; a black body disposed over said hot junctions; and a body having an outer polished surface disposed over said cold junctions; said blower serving to force a gaseous current over I said black body and over said polished surface,

the upper face of said sensing unit being unobstructed so as to enable it to see the total hemisphere.

3. A radiometer sensing unit comprising: a base; a blower mounted on said base and including a nozzle; a relatively flat thermal resistance element mounted symmetrically in front of said nozzle; a thermopile mounted on said thermal resistance element with its hot and-cold junctions disposed on opposite sides thereof; a black body disposed over said hot junctions and a body having an outer polished surface disposed over said cold junctions; and means disposed within said radiometer for determining its temperature, said blower serving to force a gaseous current over said black body and over said polished surface, the upper face of said sensing unit being unobstructed so as to enable it to see the total hemisphere. I

JOSEPH T. GIER. I ROBERT V. DUNKLE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,077,219 Coblentz Oct. 28, 1913 1,891,039 Barton Dec. 13, 1932 2,305,396 Volochine Dec. 15, 1942 2,547,173 Rittner Apr. 3, 1951 OTHER REFERENCES General Theory Design and Construction of Sensitive Vacuum Thermocoup1es, an Article by C. H. Cartwright, in Review of Scientific Instruments, vol. 1, 1930.

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