Cathode-ray Oscillograph Research Articles

Determination of Air Velocity by Ion Transit-Time Measurements

A method is described for measuring the velocity of an air stream by producing positive ions at one point in the flow and measuring the time required for the ions to be carried to an induction-type detector located a known distance (0.5 to 2.0 inches) downstream. Positive ions are produced intermittently near the tip of a positive corona point by burst discharges which are initiated by stray ions in the air stream or by irradiating the air in the neighborhood of the positive corona point with polonium alpha-particles. The ion transit-time is measured by observing the induced pulses from the detector on a cathode-ray oscillograph sweep which is triggered by the burst discharges of the corona point. The accuracy of velocity measurement using a measuring length of one inch with a free-stream air velocity of 1730 feet per second (based on pressure and temperature measurements) was better than two percent. It is shown that the direction of streamlines in a supersonic flow can be determined approximately by aligning the corona point and the induction detector probe to give the maximum amplitude of induced pulses. It is believed that this method may be applied to map velocity fields in supersonic wind tunnel experiments.

An electronic phonocardiograph employing a double-beam cathode-ray oscillograph as the recording device.

An electronic phonocardiograph employing a double-beam cathode-ray oscillograph as the recording device.

The value of high fidelity electrocardiography using the cathode ray oscillograph and an expanded time scale.

The cathode ray is practically free from inertia and therefore an ideal instrumentality for studying variations in electrical potential. A cathode ray oscilloscope with an amplifier system of high frequency response and an expanded time scale, 330 mm. per second, were employed to record electrocardiograms. Such tracings revealed considerable notching, slurring, and other peculiarities not seen in the conventional electrocardiographic records on the same individuals. An instrument should have a frequency response curve flat to well over 330 cycles per second to record faithfully the human electrocardiogram. This is much higher than the frequency response of instruments usually used for electrocardiography.

Cortical response to intermittent stimulation with colored light in the cat.

The effects of spectral lights of various wave-lengths upon the electrical activity of the cat's cortex were investigated. The light was interrupted at various frequencies by means of an episcotister driven by a motor. The horizontal sweep of a cathode ray oscillograph was made to synchronize with the rhythm of stimulation, so that a standing image of responses was established on the screen.1. At lower frequencies of flicker, evoked potentials consisted of on-and offresponses. The latter, however, disappeared above a certain frequency between 10 and 15 cps. The critical fusion frequency seemed to lie between 25 and 35 cps.2. No pattern characteristic of the wave-length could be found. However, the amplitude of response was altered in a characteristic manner as the wavelength was systematically varied. The spectral distribution of amplitude was found closely similar to the scotopic luminosity curve.3. When strong colored lights were used, some difference in wave form could be found, but it was shown that the difference was chiefly due to the difference in luminosity.4. Responses obtained with bipolar lead were restricted to the striate and extra-striate areas. When monopolar lead was used, responses appeared over much wider regions, including the so-called auditory areas. A systematic phase difference was seen between records obtained from two neighboring areas, and this fact suggests that excitation spreads from the visual cortex into surrounding areas through some intracortical pathways.

Magnetization Hysteresis Loop Tracer for Long Specimens of Extremely Small Cross Section

An instrument for measurement of the low frequency magnetic properties of thin layers is described. The difference signal from two opposed pick-up coils, one of which contains the sample, is amplified, integrated, and amplified again to cause the vertical deflection of a cathode-ray oscillograph to be proportional to the intensity of magnetization of the specimen. A signal is applied to the horizontal deflecting plates of the oscillograph to cause it to represent the applied magnetizing field in the region of the pick-up coils. A large reduction in low frequency noise in the difference signal preamplifier is accomplished by use of a circuit similar to electrometer tube circuits. Noise introduced through integration of sharp peaked signals is reduced by use of first and third harmonic components in the magnetizing field current. A signal equal to noise is produced by a flux change of 75×10−6 maxwell.

A new method for studying mechanics of breathing using cathode ray oscillograph.

Summary(1) Pressure-volume curves of the chest and lungs may be portrayed directly on the cathode ray oscilloscope to show the elastic and viscous properties described by previous authors (1,2). Alterations of muscle tone of the thorax affect the pressure-volume curve in such a way as to aid or resist artificial respiration and are immediately detectable by this method. (2) Pressure-flow curves may be recorded in a similar manner. This method permits the easy evaluation of the constants: involved in the equation P = KV + K'V2 which are determined by the physical characteristics of the lung tree. (3) Inertia of the thorax causes a small lag between pressure around the chest and flow at the mouth. This time lag is of the order of one-sixtieth of a second.

After-potentials in the electrocardiogram.

Summary.An analysis has been made of the lingering potentials following the T‐wave in the electrocardiogram, as previously described (Sjöstrand, 1950). A positive after‐potential can be recorded both by the usual electrocardiograph with an alternating current amplifier (Triplex, Blema), and by means of a direct current amplifier, cathode ray oscillograph and subcutaneous needle electrodes.On intravenous infusion of small amounts of adrenaline, the after‐potential is greatly increased. It may be shown that it is continuous with a component, which, in the normal resting electrocardiogram, is included in the T‐wave. Increased vagus tonus appears to have the opposite effect to that of adrenaline. The typical electrocardiographic changes occurring with lowered blood potassium concentration correspond in several respects to the adrenaline effect.The positive after‐potential is not directly connected with the mechanical systole of the heart and it occurs either completely, or to the greater extent, after the refractory period. During this phase there seems even to be an increased excitability, judging from the fact that extra‐systoles may occur.The after‐potentials and their variations show a great similarity to those of nerves, Purkinje fibres and the isolated frog heart. They may explain several physiological changes in the electrocardiogram. A number of pathological deviations may also be explained from variations in these after‐potentials and so be considered in relation to the recovery processes in the myocardium following the actual action potential.

A Fast-Scanning Infrared Recording Spectrometer*

A spectrometer has been constructed to scan portions of the infrared spectrum at repetition rates up to 20 spectra per second. The optics are basically those of a Perkin-Elmer Model 12 C prism spectrometer. The electrically driven mechanical system used to oscillate the Littrow mirror provides for changing the repetition rate, the scanning interval, and the spectral region independently of one another while the instrument is in operation. A Golay pneumatic detector with a time constant of 1.2 milliseconds extends the spectral range to 14 microns with a NaCl prism. The resolving power is low by conventional standards, but is satisfactory for broad bands such as those exhibited by gases under high pressure. The spectra are displayed on a cathode-ray oscillograph and are recorded photographically. Reference marks corresponding to definite orientations of the Littrow mirror are obtained by a subsidiary optical system and are indicated as blanked spots on the oscillograph trace. A synchronized radiation beam chopper serves to indicate the zero radiation signal during the unusable portion of the scanning period. The spectrometer was designed for the study of solid propellant flames, but will also be useful for the study of fast, but not explosive, gas reactions.

A 35 mm high-speed cinematograph camera

A 35 mm high-speed cinematograph camera is described which takes full-size pictures at repetition rates from 100 to 2 000 per sec. Film capacity is 200 ft and films taken can be projected in the normal way. Optical compensation for the film movement during exposure is provided by a rotating cubical glass prism interposed between objective and film. For half-height pictures an octagonal glass prism is used and the maximum repetition rate is then 4 000 p/s. The instrument can be used with either continuous light on the subject or synchronized with the flashing light source of a high-speed power stroboscope. Removal of the image compensator permits the camera to be used as a high-speed film chronograph with a film transport speed of 125 ft/sec. Optical arrangements are made for the simultaneous photography of a cathode-ray oscillograph trace on part of the picture area. 1 000 c/s timing marks are given on the film edge.

The controlled tripping of high-voltage impulse generators

This paper summarizes the requirements of tripping circuits and spark gaps which enable a high-voltage impulse generator of one or more stages to be discharged in synchronism with the operation of such measuring equipment as a cathode-ray oscillograph or a rotating-mirror camera. A triggered spark-gap and the associated circuits which give accurate synchronism are described. A tripping pulse of only about 5 kV is required, and this may be obtained from the time sweep circuit of a high-voltage oscillograph, or from a blocking oscillator. Tripping of a single-stage generator is obtainable within 0.1 μsec of a pre-determined short delay time.

Central respiratory spike potentials.

THE exposed medulla oblongata of the dog, cat and rat was explored by means of a stereotaxic instrument carrying a unipolar steel needle electrode (diameters from 10 to 40 microns at the non-insulated tip), and fast potential changes were recorded with amplifier and cathode-ray oscillograph. Simultaneous records were taken either (1) of respiratory movements using a strain-gauge, or (2) of tidal air using an electrically recording spirometer, or (3) of the action potentials of diaphragmatic muscle units. Method (3) shows the time relations between central and peripheral events more accurately, and at the same time allows the frequencies of the medullary and spinal discharges to be compared.

Bibliography on High-Speed Photography: Including Schlieren and Cathode-Ray Oscillograph Photography

Bibliography on High-Speed Photography: Including Schlieren and Cathode-Ray Oscillograph Photography

Possibility of Measuring a Quadrupole Transition Probability from an Auroral Afterglow

THE green auroral line of oxygen at 5,577 A. (1D2 – 1D0) has been found by Vegard and Kvifte1, and Jenkins, Bowtell and Strong2 in the afterglow of a Tesla discharge through argon, or a mixture of argon and nitrogen, at nearly atmospheric pressure, when there is a minute trace of oxygen present. It is accompanied by a diffuse band similar to one described by L. and R. Herman3. We have made some measurements of the decay of this phosphorescence, which can be followed by a photo-multiplier connected through an amplifier to a cathode ray oscillograph with a low-frequency time base. Three sources have been used, namely, two 300-watt commercial Osram gas-filled lamps, and a cylindrical tube 21 cm. long and 6 cm. in diameter containing a similar gas mixture, with two rod electrodes 2 mm. in diameter, mounted near one end with their tips 3 cm. apart. The photomultiplier was exposed to the glow from a volume of gas about 3 cm. in linear dimensions.

A Rapid Scanning Spectrometer for Oscillographic Presentation in the Near Infra-Red*

A rapid scanning spectrometer for oscillographic presentation has been built for use in the “photo-conductive” infra-red region. It is designed to present spectra from 0.36μ to better than 5μ using a PbTe cell. The CO2 doublet at 4.2μ is resolved with a scanning rate of 120 cycles per second and a scanned interval of better than 1.5μ with fluorite optics. A wave-length calibrating device has been incorporated into the instrument; this presents a fiduciary scale, synchronized with the spectrum, on the second beam of the twin-beam cathode-ray oscillograph. Adequate solutions have been found for the problems of synchronizing oscilloscope sweep and scanning drive, and for the problems of amplifier design for the sensitive cells.

Measurement of secondary electron emission from dielectric surfaces.

A technique is developed for the rapid and precise measurement of the secondary electron emission properties of certain dielectric surfaces. The dielectric surface is bombarded by primary electrons having energies which produce a secondary emission ratio greater than unity. This establishes the surface potential at a known value. With the known potential difference between the dielectric surface and primary electron source, the energies of the primary electrons are automatically determined for the first instant of surface bombardment. The net current to the dielectric surface at any moment is measured by using a cathode-ray oscillograph to observe the transient current to a metal plate which backs the dielectric. The method has been used to study metallic surfaces and has yielded results which agree very closely with those obtained using the conventional d.c. method of measurement.

An Electrostatic Fluxmeter of Short Response-time for use in Studies of Transient Field-changes

The fluxmeter consists of a conducting system of small capacity which is alternately exposed to and screened from the electric field by the movement of a rapidly rotating metal shield, thus producing an alternating E M F. of period 0.83 millisecond The output, after amplification, is displayed on the screen of a cathode-ray oscillograph and the record carries an automatic indication of the sense of the field every 7.5 milliseconds At the maximum sensitivity employed the device gives a deflection of one centimetre in a field of 20 volts/metre, with a background noise-level of 0.15 cm. (3 volts/metre). The response-time of the instrument is one half-cycle (0 42 millisecond). The fluxmeter has been developed to give the rapid response and high sensitivity required for studies of the electric fields of thunderstorms in the intervals between the separate strokes of a lightning discharge.

Vibration Studies: Related to Electron Microscopy

This paper describes a convenient scheme for detecting and measuring vibration as related to the performance of an RCA electron microscope (Type EMU). The procedure involves the use of a Webster Model F5P2 phonograph pick-up arm in conjunction with a cathode-ray oscillograph. The cathode-ray oscillograph signal amplitude which represents the vibration of the location being investigated was calibrated by means of a Brush Development Company Type BL-301 vibration pick-up whose voltage output is proportional to the product of the vibration amplitude and the square of the frequency. An audio oscillator was used to calibrate the voltage output of the Webster (rochelle salt) pick-up as a function of frequency. After calibration, these oscillographic measurements may be used to determine absolute mechanical displacements. Electron micrographs are included to illustrate the image displacements due to several different amplitudes of vibration. Cognizance of vibration is often necessary, especially in high resolution electron microscopy. This scheme may be used as a guide in high resolution electron microscopy.

A Photoelastic Dynamometer for Rapidly Varying Forces

A photoelastic dynamometer applicable to rapidly varying forces is described. It consists of a glass slab upon which the force acts, placed between crossed polarizers; the intensity of the transmitted light is a measure of the force. It is indicated by a vacuum photocell working on an amplifier and a cathode-ray oscillograph. The arrangement has been used for recording the variation of pressure over the area of contact in rolling mill research. Compared with piezoelectric methods, it has the advantages of stability and of applicability to moving components without the necessity of using slip-rings.

A Photoelectric Investigation of the Cool Flame of Ether

A method is described, in which the light from a cool flame under the form of a static, uniform glow is measured as a function of time by means of a multiplier photo-tube and a single-sweep cathode-ray oscillograph. The circuit embodies an a.c.—d.c. amplifier and a slow sweep. Cool flames of diethylether-oxygen mixtures in a Pyrex cylinder 4.6 cm in diameter have been studied under the following range of conditions: 180–250°C, 0–150 mm and 5–95 percent ether. The pulsating glow, which lasts about 1 second, shows two and sometimes more maxima. The generally accepted lower pressure limits appear as regions of feeble but smoothly decreasing intensities. Under the conditions of our experiments, the temperature coefficient is negligible. Both intensity and integral emission increase regularly with the concentrations of the reactants and are maximum at 50 percent ether by volume, the variations being roughly symmetrical with respect to the partial pressures of either component. Variations of pressure and composition cause regular but considerable changes in the shapes of the oscillograms. Light and pressure pulses follow each other closely, suggesting that the latter are of mainly thermal origin and that the light intensities reflect the instantaneous reaction rates. The glow lasts longer in the wider vessels. In the presence of the reaction products, it either fails to appear or emits the normal amount of light. A preliminary analysis of the quantitative data is given and possible interpretations, in terms of oxidation mechanisms, are discussed.

Duration of Lightning Strokes and Occurrence of Multiple Strokes

It is shown that the total duration of lightning strokes, the occurrence of multiple strokes and the time interval between them are partially influenced when measurements are made on direct strokes to tall objects. By recording the radiated electromagnetic field of lightning discharges in antenna circuits with cathode ray oscillographs at great distances from the lightning paths it was possible to obtain extensive data on the variation characteristics of lightning. Special methods were developed in order to analyse the lightning discharges with regard to the sequence of multiple strokes and the slow moving after-variation. A comparison of the discharge characteristics of lightning in Sweden with corresponding results from lower latitudes leads to the assumption that the intensity of thunderstorms is greater in low latitudes than in high latitudes. This involves researches of a geophysical problem of greatest interest from different points of view. DOI: 10.1111/j.2153-3490.1950.tb00308.x