Showing papers on "Rise time published in 1972"

A low-cost millimeter-wave glow-discharge detector

Abstract: A low-cost millimeter-wave glow-discharge detector characterized by a responsibility of 0.177 V/W, a rise time of 2.5 µs, and a noise equivalent power (NEP) of ∼10-13W/Hz when used in a synchronous detection mode is described. Low NEP is accomplished through a novel biasing arrangement of a commercially available three-electrode glow-discharge lamp originally intended for triggering applications. This biasing arrangement leads to rms noise voltage suppression of nearly 20 dB. This, together with other known properties, makes this detector particularly suited for use in closed-range microwave hologarphic arrays.

Interrelations Between Amplitude, Latency, Rise Time, and the Edelberg Recovery Measure of the Galvanic Skin Response

Abstract: This report describes relationships between the Edelberg recovery measure, latency, rise time, and amplitude measures of GSR response to cued, uncued, and disparity USs. Under cued and uncued conditions all temporal measures were independent of amplitude. Rise time and recovery measures were highly correlated under all conditions, while correlations between latency and rise time or amplitude were quite weak, suggesting that latency and rise time-recovery are partly under the control of different mechanisms. When US was unexpected (disparity), latency remained independent of amplitude, but significant correlations developed between amplitude and the temporal measures of rise time and recovery. Latency and recovery, but not rise time or amplitude, distinguished between disparity and non-disparity conditions. The results demonstrate the need and utility for more complete response specification.

Effect of Pulse Rise Time on the Response of Corona Detectors

Abstract: The response of RCL corona-pulse detectors is investigated as a function of the calibration-pulse rise time. Excitationpulse rise times ranging from 0.05-50 ?s are employed and the resulting signal response waveform and magnitude are recorded. The peak response is found to diminish appreciably with the rise time for values in excess of 1.0 ?s; significant response waveform changes are manifest with rise times greater than 3.0 ?s. A multichannel pulse-height analyzer is utilized to demonstrate the errors inherent in response signal magnitude distribution measurements when calibration is carried out with square pulses having different rise and decay times.

Measurement of the pyroelectric coefficient and permittivity from the pyroelectric response to step radiation signals in ferroelectrics

Abstract: A method is presented of measuring the pyroelectric coefficient λ and permittivity e from the initial slope, rise time, and peak value of the pyroelectric response to step radiation signals, valid for temperatures up to the Curie point. An experiment carried out on single‐crystalline triglycine sulphate has yielded the temperature dependence of λ and e with reasonable accuracy and in good agreement with other methods.

The electric strength of Perspex as a function of voltage rise time

Abstract: The electric strength of Perspex was measured using impulse voltages reaching their maximum values in times ranging from 05 μs to 10 000 μs. For sphere-sphere electrodes the electric strength is 60 MV cm−1 at the shortest rise time, 131 MV cm−1 at 177 μs, and 84 MV cm−1 for slowly rising direct voltage. Similar trends were found for point-plane electrodes. The results are consistent with a rapid accumulation of negative space charge close to the cathode, and a positive space charge close to the anode.

High Speed Inexpensive Photodiode Assembly

Abstract: A photodiode assembly is described which incorporates a Hewlett‐Packard 5082–4220 diode in an impedance matched holder to produce a unit with a rise time of approximately 100 psec and a fall time of approximately 300 psec. The assembly was designed for detecting fast laser pulses, but it can be used for monitoring any high speed optical signal.

Rise time of pulsed parametric oscillators

Abstract: General relations are derived that describe the rise time of the output power of parametric oscillators driven by a time-dependent pump. Both singly resonant and doubly resonant oscillators are discussed. Results of computer calculations using a Gaussian time envelope for the pump pulse are presented and, in the case of the doubly resonant oscillator, are compared to predictions of a steady-state analysis. Agreement between calculated rise times and published values is good.

Laser q-switching

Abstract: A transformer-driven electro-optic Q-switching arrangement reduces the high-voltage switching requirements with greatly simplified circuitry. Lasing efficiency is not significantly reduced even when the transformer rise time is twice as long as the laser pulse build-up time.

In-line pole-zero conditions to ensure non-negative impulse response for a class of filter systems†

Abstract: In the design of filters for which it is required that there should be little or no overshoot of the transient response for a step input, it is common practice to adjust parameters so that the binomial filters are realized. This results in relatively slow rise times, but ensures zero overshoot. It is shown in this article that very much faster rise times can be obtained by pole-zero configurations which ensure a non-negative impulse response. The concept differs from traditional methods and also shows that intuitive notions of the response for given pole-zero distributions can be misleading.

Drive circuit for inductive load

Abstract: A drive circuit for an inductive load is described which has particular use for stepping motors. A high voltage power supply is connected through a very low impedance directly to the inductive load to provide a fast rise time for the load current. When the current exceeds a predetermined value, the load is disconnected from the power supply. The current induced in the load due to flux decay is permitted to circulate through the load and a current sampling circuit. When the induced current drops below a minimum value, the load is again connected to the power supply for a period sufficiently long to allow restoration of the load current to the desired value. The circuit utilizes two switches to control the flow of induced current and connection of the load to the power supply. Both switches respond to a logic signal indicating that the load is to be energized. One switch is used to control the induced current and the other is used to make the connection to the power supply.

Improved Amplitude and Rise Time Compensated Timing with Ge Detectors

Abstract: The energy range over which signal timing can be made nearly independent of amplitude and rise time has been extended downward by about an order of magnitude by employing dual priming of a zero crossing discriminator. By introducing another coarsely compensated timer between the high resolution timer and its priming leading edge discriminator, one can optimize the timing accuracy without sacrifice of dynamic range. Time walk of less than 1 ns has been achieved from about 20 keV to over 1 MeV.

The influence of rise time on loudness.

Abstract: The influence of the rise time on the loudness of sound pulses and the meaning of the sound spectrum on this influence were examined. A “paired comparison” method was used. The sound pulses had a duration of 0.7 to 1.0 sec and the rise time was varied between 0.03 and 1.0 sec. For most of the measurements, a signal level of 95 dB re 2×10−5 N/m2 was used. The signals with the fastest onset showed the highest loudness. The influence of the rise time on the loudness was significantly dependent on the signal spectrum. The possibility of explaining the observed effects on the basis of changed synchronism of the neural activity and on the basis of a rapid adaptation in the nervous system is discussed.

A Pattern Search Algorithm for Feedback-Control System Parameter Optimization

Abstract: The problem of parameter optimization for the purpose of synthesis and design of feedback control systems is considered. A flexible performance index, which permits direct consideration of performance specifications such as rise time, settling time, peak overshoot, and bandwidth, in addition to the usual analytic forms, is developed and adapted to a modified version of Rosenbrock's pattern -search algorithm. Modifications of Rosenbrock's method include: 1) scaling of parameters to ensure coordinate orthogonalization; and 2) employing variable step sizes at the beginning of each new stage, the steps being a function of previous failures and successes. The efficiency of each stage is thus improved and the sensitivity to initial estimates of step size is reduced.

High frequency power generator

Abstract: A static inverter system capable of providing ac. power at frequencies as high as 10 KHz. is characterized by an exceptionally high power factor and efficiency and employs one or more capacitive storage circuits on a time sequenced basis to cyclically and successively charge from a dc. power supply and discharge through an ac. load. The storage circuit charge via respective thyristors and the sequencing is affected by sequentially gating the thyristors with fast rise time, short duration firing pulses so that very short charging time constants may be selected without danger of damaging the thyristors or upsetting the desired sequencing.

Improvements relating to target discriminating devices

Abstract: 1298061 Proximity fuses EMI Ltd 1 June 1961 [9 June 1960] 20401/60 Heading F3A [Also in Division H4] A target discriminating device comprises radiation detecting means, means for condensing incident radiation on the detector, and means for providing a predetermined output signal only when the incident radiation affects an area of the detector within prescribed limits of size and within a predetermined time or times. In one arrangement, Fig. 1a, the discrimination is based on the size of the image. The detector is divided into five separate areas, a central area B and four surrounding areas D-G. The output from the central area B may be fed to a fusing circuit through four switches in series, these switches being controlled by the outputs from D-G respectively; thus a fusing signal is produced only if all five areas are energized, and it is assumed that the image of a target P will cover all five areas whilst the image of a spurious source T will cover only the central area. In an alternative arrangement, Fig. 4 (not shown), a detector assembly comprises a lens and three detectors, the two outer detectors performing the function of the areas D-G of Fig. 1a, and a plurality of assemblies are located about the periphery of a missile. In a modification, Fig. 5 (not shown), a single set of three detectors is surrounded by a single optical arrangement which focuses incident radiation from all directions round the axis on to the detectors. The arrangement shown in Fig. 2 comprises a lattice of horizontal and vertical conductors which are connected together at the cross-over points by radiation-sensitive cells. The horizontal conductors are connected to the " two " gates 60 as shown, and the vertical conductors are connected to a counter 59 which applies a voltage pulse to each in sequence. When a pulse is applied to one of the vertical conductors it is applied to all the horizontal conductors, and if any of the cells is energized the pulse is superimposed, on the respective horizontal conductor, on the voltage from the cell. The threshold of gates 60 is adjusted so that a gate will produce an output signal in response to a voltage pulse from the counter when that pulse, as applied to the respective two horizontal conductors, is superimposed on the voltages caused by the simultaneous sensitization of the two cells coupling the vertical conductor and the two horizontal conductors. The output sides of gates 60 are connected through a gate 61 to a storage circuit 62 which has a short rise time and a long decay time and which produces a signal proportional to the sum of the individual pulses received from gate 61 if they follow at the repetition frequency of the counter 59. The amplifier 63 has a threshold such that a signal is produced if the sum output of circuit 62 corresponds to that produced by a predetermined number, e.g. two, of successive pulses from gate 61. In a modified lattice arrangement, Fig. 3 (not shown) each horizontal conductor is connected to a mono-stable device or flip-flop having a time constant greater than the cycle period of the counter. Thus an image on a single radiation-sensitive cell will produce an output on the first scanning cycle but not on the second. The outputs of the mono-stable devices are fed to a frequency discriminator which produces an output if signals recur at the cycle frequency of the counter. This arrangement therefore produces an output signal in response to images which cross the lattice or grow in size at a greater speed than a predetermined minimum.

Circuits for Pulse Rise Time Discrimination in Proportional Counters

Abstract: It is possible to distinguish X-ray events from particle events in proportional counters on the basis of the difference in rise time between the pulses that result from both kinds of event. A number of different circuit configurations for achieving rise time discrimination have been evaluated and their performance compared. Rise time spectra of Fe55 and Co60 have been obtained in several different gas mixtures.

Detection Efficiency of Electron Multipliers for Low-Energy Electrons

Abstract: Pulse‐height spectra have been obtained for electron multipliers with discrete dynodes of CuBe. A peak in the spectrum shows up at low pulse heights (≈ 0.1 pC for a multiplier with a dc gain of about 106), but a long tail extends out to very large pulses. These observations can be understood in terms of secondary emission processes. They have provided a good basis for the design and calibration of a soft particle spectrometer for the ISIS‐2 satellite. The detection efficiency for 300‐eV electrons, with a 14‐stage venetian blind multiplier having a total gain of 106, is about 80%. Below 100 eV the detection efficiency falls off, but in practice this can be overcome by postacceleration. At higher energies it also decreases to about 30% at 4 keV. This efficiency is reduced at very high counting rates, above 107 sec−1, owing partly to amplifier bandwidth limitations related to noise immunity requirements, and partly to the finite rise time of the multiplier pulses.

Shaping Fast Rise-Time Pulses with Tapered Transmission Lines

Abstract: For the purpose of checking very fast time-domain reflectometer (TDR) systems it is desirable to have a fast rise-time pulse whose parameters are known. A means for obtaining pulses meeting these requirements has been achieved by suitably tapering the inner conductor of a rigid coaxial transmission line having air dielectric, commonly referred to as an air line. The air line is driven with a pulse that has a very fast rise time compared to the rise time of the expected output pulse. A reflected pulse will be generated whose shape is dependent upon the taper of the inner conductor. A procedure is outlined for determining the proper taper to shape the leading edge of the reflected pulse to match any continuous single-valued function. Air lines that were designed and built for producing a pulse whose leading edge is a linear ramp, a truncated Gaussian function, and the integral of a truncated Gaussian function are discussed and traces of these pulses are shown. The problem of re-reflections due to the multiple discontinuities along the air line was analyzed by means of a computer. This program is described. The effect of the driving-pulse parameters on the reflected pulse is analyzed on a theoretical basis. Rise time, pulse shape, and aberrations such as overshoot and ringing of the driving pulse are considered in this analysis.

A coaxial capacitive voltage divider for oscilloscopic recording of nanosecond high voltage pulses

Abstract: A coaxial capacitance voltage divider with a ratio of 110 and a rise time much less than 2.5 ns was developed for use with a transmission line pulse generator capable of producing 100 kV rectangular pulses of 2 mu s duration. The low voltage arm of the divider is a 3 cm long tube of titania (TiO2) turned out from a cylindrical compact. The compact was made by first pressing titania powder using a suitable binder and then sintering at controlled temperatures. The tube was slipped over the terminating end of the pulse-forming cable to form the divider with the cable capacitance.

Design of Rectangular Current Capacitor Banks

Abstract: The design equations for a capacitor bank current source capable of producing an essentially flat‐top, kilo‐ampere‐range current pulse having a duration of the order of tens of microseconds are presented. Magnitude, rise time, duration, and droop of the pulse are considered.

Pulse generator of x-rays or fast electrons

Abstract: 1283318 Supply systems for X-ray apparatus V A TSUKERMAN N V BELKIN V I KOLESOV V V BOGOLJYBOV E A AVILOV V N VOLGIN E D KOCHETKOV N I OGORODNIKOV D M CHISTOV 8 Jan 1971 [8 Jan 1970] 970/71 Heading H2H [Also in Division H1] An irradiation tube 7, Fig. 2, for producing X-rays or fast electrons is energized from a pulse transformer 3 through an enclosed spark gap 6. The irradiation tube is shunted by a resistance 9, and a capacitance 10 is provided by the envelope of the spark gap 6. A capacitor 22 is charged to 5 kV. from a rectifier circuit and discharged via switch 23 and the pulse transformer to produce a pulse with a microsecond rise time and an amplitude of 150 kV. across the secondary winding 13. After the breakdown of the spark gap 6 a voltage of the same amplitude and a rise time of 1 to 3 nanoseconds is applied to the cold cathode 8 of the irradiation tube.

Variable Frequency Three-Phase Square Wave Generator with Fixed Phase Sequence

Abstract: The design of a three-phase square wave generator with continuously variable output frequency in the 40-400 Hz range is described. The basic generator circuit consists of an astable multivibrator, and a divide-by-three logic network followed by a divide-by-two logic network with a synchronizing gate. Frequency control is arranged in the multivibrator. The synchronizing gate assures fixed output signal phase sequence. Noninverted and inverted output is available. In order to provide adequate output power, push-pull load driving stages preceded by emitter followers are incorporated. Transformer coupled output is used in the prototype to drive SCRs in a high-power three-phase static frequency changer. Custom wound toroidal core transformers have been used. The rise time of the square wave at the generator output is below 3?s.

Step-Function Response of a Line with Ground Return - Empirical Vs. Asymptotic Approximations for Impedance

Abstract: A first-order asymptotic approximation to the distributed series impedance of an overhead transmission line with ground return (frequency-dependent resistance) is insufficient for the prediction of the step-function response at distances of a mile (1. 6km) or more from the source. Series solutions based on a third-order asymptotic impedance approximation have useful convergence properties only for distances up to perhaps three miles. An empirical impedance function, designed to approximate the true function closely over a finite band of somewhat more than one decade, and utilizing corrective terms proportional to s exp (?k, s) and s exp (?k2 s), yields a series solution which is usable for much longer distances. These series solutions predict a more rapid rise in voltage than does the first-order asymptotic approximation and they indicate that, at distances of more than a few miles, rise time tends to be directly proportional to the distance.

An Apparatus for Producing Mechanical Step Pulses for Biorheologic Studies

Abstract: A device to produce displacement step pulses for studying viscoelastic wave propagation in biological specimens was developed on the basis of condenser discharge through a solenoid. The amplitude and rise time of the pulse step can be adjusted by varying the condenser capacity, charging voltage, and distance between the armature and the electromagnet.

An electron-dispersion tube for the observation of subnanosecond transient signals

Abstract: The device described increases the effective bandwidth of a real-time oscilloscope so that transient signals of much smaller rise time than that of the oscilloscope can be observed. An effective bandwidth multiplication factor of 10 was obtained with the prototype tube.

Photoelectric methods and apparatus with contrast enhancement

Abstract: Response contrast of photoelectric processes is enhanced by selecting photoelectric systems having different rise times for different light input intensities, and by exposing the photoelectric systems during periods of time which are shorter than the rise time for a lower light intensity or which are at least as short as the rise time for a higher light intensity. Bright spot detection systems and magnetic imaging or recording systems employing these rise time phenomena are also disclosed.