ISSN:0034-6748    

DOI:10.1063/1.1769771

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

Details are given of the construction of a gauge for measuring the thickness of monomolecular films by means of the interference of light. The intensity of monochromatic light reflected from a thin film of a transparent material varies with the thickness of the film according to a cosine curve. When light strikes a film at an angle of incidencei=15°, the variation of the logarithm of the intensity with thickness is greatest at thicknesses 0.75&lgr;/4nand 1.282&lgr;/4n, wherenis the refractive index of the film. In order to bring the thickness to this critical value a silica film was developed on lead glass by treating the glass with HNO3. Monolayers of various substances can be deposited on top of the silica film, and the thickness of the monolayer determined from the change in intensity of reflected light produced by the added thickness. The change of intensity can be determined very accurately by a method of measuring the ``match angle'' at which two steps of different thickness reflect light of equal intensity. When this angle can be measured with an accuracy of ±10′ the thickness of the added monolayer is known with an accuracy of ±0.76A. Equations are given for calculating thickness.

ISSN:0034-6748    

DOI:10.1063/1.1769772

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

Rotors freely suspended in high vacuum were driven to high rotational speeds by electrostatic and by electromagnetic forces. The first suspension used was a modification of the photoelectrically stabilized suspension developed in this laboratory by F. T. Holmes. Another magnetic suspension was developed which was stabilized by capacity coupling. The electrostatic drive consisted of a charged bisymmetrical blade free to rotate between quadrant plates to which were applied alternating potentials generated either by interruption of a beam of light by the rotor, by capacity pick‐up, or by an external oscillator. Rotors were also driven by rotating magnetic fields. Objects suspended varied in weight from 7 g to 1200 g. The highest speed attained was 3200 r.p.s. using a 14‐g rotor. A deceleration of 2.2×10−4rev./sec.2was measured with a 47‐g rotor (moment of inertia, 103 g cm2) running at 650 r.p.s. with no applied torque.

ISSN:0034-6748    

DOI:10.1063/1.1769773

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

In designing a new radiation pyrometer for industrial use above the lower limit of visible radiation, consideration of ambient temperature effects, which is of much importance in modern industrial practice, was carried out by aid of mathematical analysis. In one hypothetical case, with a very sensitive type of thermopile losing heat from its hot junction by radiation alone, it is shown that an increase in operating ambient temperature of 180°F (from 80°F to 260°F) results in a drop in output voltage of 38 percent for a constant furnace temperature of 1300°F. The corresponding error in reading is 315°F. At a furnace temperature of 3000°F, the decrease in voltage is 17 percent and the error in reading is 387°F. Under similar conditions, in another hypothetical case of a less sensitive thermopile constructed to lose much of its heat by thermal conduction, this 180°F increase in operating ambient temperature would result in a decrease in output voltage of from 12.2 percent to 12.5 percent for any furnace temperature between the two values mentioned. The error in reading would range from 58°F to 162°F over the stated span of furnace temperatures. The constancy of ratio of e.m.f.'s shown for the higher conduction factor makes it possible to provide ambient temperature compensation over a wide range of furnace temperatures with a nickel shunt compensator. The pyrometer here described, designed along these lines, shows ambient temperature errors of less than three degrees F in the furnace temperature being measured for ambient temperature variations from 50° to 200°F; transient errors would usually be one degree or less for most cases; the response is complete within 3.5°F in four seconds and within half a degree or less in six seconds. The calibration, with varying ratios of distance‐to‐targetversustarget diameter up to over 20 to 1, is unusually constant. A thermopile of ten units insures ample e.m.f. All of the thermopile junctions are spot‐welded and the construction is arranged throughout to withstand high ambient temperatures.

ISSN:0034-6748    

DOI:10.1063/1.1769774

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

(1) An inexpensive optical system suitable for use with an air‐driven ultracentrifuge is described. (2) Sedimentation pictures of inorganic colloid systems indicate the quality of sedimentation pictures possible with this apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1769775

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

A pulse sharpener equalizer capable of producing sharp pulses whose amplitude and width are independent of the wave form of the input signal is described. Input pulses having a width of 100 sec. to 10−4sec. work equally well and a change of bias permits operation with either positive or negative input pulses. The circuit uses all hard tubes and gives output pulses of either sign essentially the same in form as the interstage pulses in a scaling circuit, hence the resolution of the scaling circuit is not impaired by the use of the sharpener.

ISSN:0034-6748    

DOI:10.1063/1.1769776

出版商:AIP    

年代:1941

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1769778

出版商:AIP    

年代:1941

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1769779

出版商:AIP    

年代:1941

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1769780

出版商:AIP    

年代:1941

数据来源: AIP