摘要:

A design for an extensometer for measuring lateral deformations in brittle materials using LVDT's is presented. The system is sensitive enough to measure the small changes in diameter that occur in such situations, but is simple and inexpensive. The instrumentation technique also allows a choice of electronic equipment, thus making it more versatile. The extensometer may be used for lateral deformation measurements in both compression and tension experiments.

ISSN:0034-6748    

DOI:10.1063/1.1720886

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The principles of a new method for the detection and measurement of potential difference are given, together with a description of a prototype instrument. The basis of the method consists of the use of two cyclically varying capacitors in conjunction with two resistors, or equivalent elements, to provide an ideal transducer. Devices based on this principle have input resistances which are limited only by leakage from the input conductor, and are suitable for measurements in circuits of very high resistance. Important features of the new arrangement are a completely passive input equivalent circuit, a short response time, and an improved signal‐to‐noise ratio as compared with existing electrometers.

ISSN:0034-6748    

DOI:10.1063/1.1720887

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A compact apparatus enclosed in a stainless steel vacuum chamber was used to measure the 8–13 &mgr; emittance of silicate powders under simulated lunar conditions for purposes of compositional analysis. Samples with surface temperatures as low as 180°K could be measured. The sample was contained in the removable lid of a constant temperature bath and its upper surface allowed to radiate into a cavity maintained at liquid nitrogen temperature (77°K). The spectral emittance was computed by matching the observed spectrum with a Planck function at high emittance wavelength intervals. System response was determined with an internal calibrating blackbody maintained at 273°K.

ISSN:0034-6748    

DOI:10.1063/1.1720888

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An improved sensor and calibration techniques for the measurement of infrasonic and gravity waves are described. The sensor is a modified, Moore sailplane rate‐of‐climb indicator, which produces a linear electrical output for pressures between 103and 10−2dynes/cm2, with a flat frequency response between 22 and 0.001 cps. It is a stable instrument, light and easily adapted for balloon payloads and other field experimentation. The calibration techniques provide controlled sinusoidal pressure at various simulated altitudes and atmospheric temperatures. Several present and future applications of the techniques are discussed, as well as some of the methods used in these applications to effectively control wind, temperature, ground motion, and other extraneous noise sources.

ISSN:0034-6748    

DOI:10.1063/1.1720889

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A new automatic instrument for the measurement of surface temperatures is described. The instrument examines for polarization the sum of (1) radiation emitted by the test surface and (2) radiation emitted by a blackbody and reflected from the test surface. In measurements up to 450°C on metallic surfaces with emittances of 0.05 to 0.47, the determination of equality of sample and reference temperatures was accurate within about ±2%, with no emittance corrections. Further tests are required to apportion this error among sample surface characteristics, instrument characteristics, and experimental error. Away from the null, the error signal depends on the difference of the emittances &egr;pand &egr;s.

ISSN:0034-6748    

DOI:10.1063/1.1720890

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Present high gain cryotron amplifiers use dc biased cascaded crossed film cryotrons, and cannot be operated below 1 kHz because of low frequency noise. It is shown that in situations where minimum input inductance is not required, a much simpler circuit, using a crossed film cryotron with many crossovers, can be used as a single stage high gain amplifier. It is found that, if gate bias is applied in the form of pulses, helium bubble formation, which is the cause of low frequency noise, is inhibited. Also the chopping action of the gate pulse allows the amplification of dc signals. The multicrossover cryotrons described have 512 crossovers and exhibit bandwidths of 1 MHz and transimpedances of up to 10 mV/mA. It has been possible to explain their nonmonotonic gain‐temperature dependence in terms of penetration depth and thermal propagation effects.

ISSN:0034-6748    

DOI:10.1063/1.1720891

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A device for the measurement of rapidly varying counting rates is described. The input signals, which need not be of constant size or shape, are converted into pulses of constant width and constant current. The pulses are applied to an integrating capacitor where, at the end of an integral period, the voltage of integration is sampled and stored. The sample is in storage for an integral period and is displayed on a chart recorder, while the integrator is accumulating counts for the next sample. With this method the recorder is required only to indicate the number of counts per period. The device has been used in conjunction with a conventional scintillation counter, a radio‐active tracer, and a chart recorder to obtain an instantaneous and permanent record of blood flow patterns in the heart.

ISSN:0034-6748    

DOI:10.1063/1.1720892

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The construction of a low friction, air supported pulley for use in floating wire measurements and the methods used to test its performance are described. The quality of the results obtainable in floating wire measurements with such an air bearing is illustrated by several measurements performed on a 100 cm radius, 180°, double‐focusing magnetic analyser at the Rutherford High Energy Laboratory. The use of bearings of this type as pivots for bullion balances, and the possibility of employing such a modified bullion balance to measure the Newtonian constant of gravitationGto increased accuracy are considered.

ISSN:0034-6748    

DOI:10.1063/1.1720893

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

By varying certain design parameters of an iodine‐vapor‐filled uv photon counter of the Geiger‐Mu¨ller type, especially adapted to detect Lyman‐&agr; photons (1216 Å), it is found that the characteristic curve of the counter can be modified. The aim of the observations reported in this paper was to adjust the design parameters in order to obtain the most satisfactory characteristic curve.

ISSN:0034-6748    

DOI:10.1063/1.1720894

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A compact bidirectional detector of ultrasonic particle motion in solids has been developed and used in connection with a three‐dimensional seismic model study. It comprises a matched pair of bimorph crystals and sum and differencing circuits to separate vertical and horizontal motions. The ability of the apparatus to display motion trajectories similar to those predicted by theory is demonstrated.

ISSN:0034-6748    

DOI:10.1063/1.1720895

出版商:AIP    

年代:1967

数据来源: AIP