摘要:

This paper describes a simple feedback circuit for the hot wire Pirani gauge. This gauge is used for measurement at low pressures where the heat conducted away from a thin hot wire is a function of the gas pressure. The wire is included in a Wheatstone bridge circuit which serves both to heat the wire and to measure its temperature. In the circuit described here the heat input is adjusted automatically so as to keep the wire temperature approximately constant over a wide range of pressure changes. This is achieved by supplying the power from a magnetic amplifier which is controlled by the wire temperature, a fall in temperature increasing and a rise in temperature decreasing the power supply.In this way pressure measurements can be made over the range zero to 3 mm Hg with wire temperatures of the order of 50 to 100°C by using either the feedback signal or the power output from the amplifier to give a measure of the pressure.

ISSN:0034-6748    

DOI:10.1063/1.1715828

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A photoelectric guider system used in connection with a star camera on the 18½‐inch refractor of the Dearborn Observatory is described. The guider uses a pyramid with four phototubes to determine the error‐signals in both coordinates. Commercially available servomotors mounted on the double‐slide plate‐holder receive these signals and adjust the plate carriage to achieve a ``central balance‐point'' upon the guide‐star. The guiding action is continuous and operates on stars down to the 8th magnitude.

ISSN:0034-6748    

DOI:10.1063/1.1715829

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The construction and performance details of a simple and economical bicycle ergometer for performance of controlled recumbent exercise incident to human physiological experiments are reported. Bicycle sprockets are geared by a chain drive to the shaft of a 6‐volt automotive generator, which has been transformed into an eddy current dynamometer, suitably mounted on the chassis via separate external bearings. This permits free forward rotation of the external casing and measurement of the downward thrust of a torque arm (welded to the casing) on an overhead‐suspended spring balance. Absorbed power (work required to operate the pedals) is varied electrically by passing a 110 ac power source through variable voltage and stepdown transformers (output range selection 0 to 20 v) and a rectifier into the generator. At rotational speeds of 40 rpm (metronome timed) the work range may be selected from 340 to 5741 ft‐lb per min, with increments as low as 42 ft‐lb. The apparatus provides 95% linearity through the 360‐deg cycle at rotational speeds of 30 to 60 rpm in a work range of 340 to 5100 ft‐lb per min.

ISSN:0034-6748    

DOI:10.1063/1.1715830

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A versatile apparatus is described for use in studying electroluminescence and electrophotoluminescence. Measurements of light emission can be made with electrical excitation frequencies ranging from dc to 400 Mc and also in selected microwave bands. Oscillators that may be employed over this frequency range are discussed. The apparatus consists of a crystal mount and a simple optical system for irradiation and for the separation of excitation and luminescent spectra. Flat plate‐type as well as long silver‐type crystals are mounted on slides which can be easily interchanged. Tests may be run from low temperatures (−70°C or lower) up to about 300°C.

ISSN:0034-6748    

DOI:10.1063/1.1715831

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A comparison type nephelometer has been designed and constructed with which turbidities are measured by both absorption and scattering of light. The especially designed cells permit accurate measurement of small changes in intensity of either transmitted or scattered light over a wide range of intensities. A single light source with a sector scanner alternately illuminates two separate optical paths for simultaneous comparison of two cells, one of which may be a standard. The intensities of the two optical paths can be varied independently for comparison measurements. A light integrating sphere with phototube assembly furnishes a single photoreceiver for the two optical paths. One such sphere compares the transmitted beams, another, the scattered beams. The reproducibility of resetting in the normal operating range is two parts in ten thousand. The apparatus will operate over a range of more than five density units. When making series of measurements, it was found possible to make and record readings for different cells every 15 sec. The apparatus was used successfully for two years in bacteriological, silica gel, and colorimetry studies. A slight modification permits measurement of the depolarization of the scattered light as well as the usual Tyndall scattering. This depolarization is measured for both polarized and unpolarized incident light, thus characterizing the size and optical anisotropy of the particles or scattering centers.

ISSN:0034-6748    

DOI:10.1063/1.1715832

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A parallel plane transmission system is described for use in high Stark field microwave spectroscopy. The planes of the system are optically flat silvered glass plates and are separated by plane parallel fused quartz spacers. The instrument gives intense sharp lines out to Stark field strengths of the order of 25 statvolts/cm.

ISSN:0034-6748    

DOI:10.1063/1.1715833

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

With coiled capillaries the basic simplicity of the Hagen‐Poiseuille flow equation can be retained at flow rates which are not achievable with straight capillaries. This fact lends itself to the design of flow metering systems (for liquids or gases) which appear to be intrinsically more reliable and accurate than many other types of systems, and which require only commonly available laboratory apparatus. One such metering system for gases is briefly described.

ISSN:0034-6748    

DOI:10.1063/1.1715834

出版商:AIP    

年代:1957

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1715835

出版商:AIP    

年代:1957

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1715837

出版商:AIP    

年代:1957

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1715838

出版商:AIP    

年代:1957

数据来源: AIP