摘要:

A tuned bridge detector with a constant band width of 5 cps for use at audiofrequencies is described. The center of this band is clamped electrically to the output frequency of the associated signal generator and deviates less than ½ cps from it. This makes manual tuning of the detector unnecessary. The narrow pass band of the amplifier reduces the noise signal to a very low value and allows detection of a ½‐&mgr;v signal across a one‐megohm input for a continuous range of frequencies from 100 cps to 20 kcps. The indicated noise level is of the order of ½ &mgr;v for the one megohm input; this is about the theoretical thermal noise value (0.41 &mgr;v for 5 cps, 1 megohm). The final detector signal can be easily used to activate mechanical drives for the two bridge controls in order to maintain balance of the bridge when the measured impedance changes or to reset to balance from an unbalanced condition.

ISSN:0034-6748    

DOI:10.1063/1.1746029

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

Apparatus has been developed which permits the collection of data with a magnetic lens beta‐ray spectrometer without requiring the attendance of the operator. The apparatus adjusts the focusing current and finds the time to accumulate a given number of counts. Forty‐five sweep speeds are possible giving momentum intervals between plotted points ranging from 0.106 gauss‐cm to 255 gauss‐cm.

ISSN:0034-6748    

DOI:10.1063/1.1746030

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

A system for the remote control of the ion source of a pressure‐type electrostatic generator is described. Control of the ion source located at the high potential is established from ground potential by means of a modulated light beam. An audio oscillator is used to modulate a light source and vibrating reed relays in the receiver are used as frequency selectors.

ISSN:0034-6748    

DOI:10.1063/1.1746031

出版商:AIP    

年代:1951

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1746032

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

Three forms of diffusion cloud chamber are described. Diagrams indicate their construction, and their operation is discussed. The direction of diffusion may be upward or downward. Various alcohols and water‐alcohol mixtures may be used. A stable diffusion cloud chamber giving tracks of the quality shown in the typical photographs is simple to construct and operate. The sensitive volume, while necessarily in the form of a horizontal region shallower than the chamber itself, can be made to include most of the chamber volume.

ISSN:0034-6748    

DOI:10.1063/1.1746033

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

A transient method is described which measures the equivalent of the polarization following application of a step voltage by recording the changing current resulting from a linearly rising potential across a dielectric cell. The circuits described permit recording over intervals from 10−3sec to several seconds and are intended for use with cells employing guard electrodes. Examples of results on dielectric relaxation in solids are given and limitations of the method discussed.

ISSN:0034-6748    

DOI:10.1063/1.1746034

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

A circuit for multiplying two varying voltages based on the ``quarter‐square'' method has been developed. A segmented nonlinear element is used for squaring, and a time‐sharing scheme permits the use of a single squaring element instead of duplicate elements as in previous designs. The circuit has a time delay of less than 40 microseconds (0–67 percent) and has an accuracy of better than ±1 percent. The original circuit was designed to operate only in the first quadrant. Various methods for including the four quadrants are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1746035

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

An instrument is described which combines a current integrating circuit and a dc amplifier to provide a continuous indication of the current being integrated. The instrument is stable, easy to calibrate, and covers a range of input currents from 0.01 to 500 microamperes full scale.

ISSN:0034-6748    

DOI:10.1063/1.1746036

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

A recording instrument for measuring the dynamic shear modulus and mechanical damping of plastic and rubber‐like materials using the principle of the torsion pendulum has been constructed. The mechanical oscillations are converted into electrical potentials for recording by a torque measuring device which is actuated by a differential transformer. The apparatus is capable of measuring the modulus and damping of materials over an extremely wide range.

ISSN:0034-6748    

DOI:10.1063/1.1746037

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

An application of the mass spectrometer to the study of the respiratory metabolism is described. In this application an unmodified mass spectrometer is used for high precision measurements of both the normal and abnormal components in the collected samples. From these data the oxygen consumption rate, the carbon dioxide formation rate, and the respiratory quotient are calculated for physiological interpretation.

ISSN:0034-6748    

DOI:10.1063/1.1746038

出版商:AIP    

年代:1951

数据来源: AIP