Showing papers on "Rise time published in 1971"

Pulse transformers

Abstract: Pulse transformers capable of transmitting substantially rectangular voltage pulses, with durations of less than one microsecond, were developed for radar applications during World War II. Their primary functions were to match the impedances of high-power microwave radio-frequency electron-tube generators to electronic pulse generators and coaxial transmission cables, and to provide polarity reversal and impedance matching functions within pulse generator circuitry. The principle contributor to the development of satisfactory pulse transformers was the development of cores of thin-gauge magnetic materials having 1 μs pulse permeabilities in the range of 500 to 3500 for flux-density changes of 10 000 G. The development of void free dry-type insulation systems made it possible to produce dry-type pulse transformers for operation at pulse voltages below 12 kV. The pulse transformer development work was paralleled by analytical work which enabled pulse transformer designers to make designs to meet the requirements of the radar circuit designers. The analysis relates the three principle pulse transformer parameters, which are magnetizing inductance, leakage inductance, and effective distributed capacitance, in combination with the circuit parameters which are source resistance, effective load resistance, and load shunt capacitance, to the rise time, top ripple and droop, and fall time of the output pulse. Pulse transformers now cover a wide range of sizes and power levels and pulse widths. Small units in computer applications may deliver only a few volts at pulse widths less than 0.1 μs. Large units in linear accelerators, however, may deliver pulse powers of 70 MW at 270 kV with a pulse width of about 3 μs.

The Effects of Signal Rise Time and Duration on the Early Components of the Auditory Evoked Cortical Response

Abstract: The effects of signal rise time and duration on the early components of the auditory evoked cortical response were studied in 20 subjects. Tone bursts were presented at 1000 Hz at various rise time...

Method for composing electrical test patterns for testing ac parameters in integrated circuits

Abstract: A method is provided for generating electrical test patterns for testing functional AC parameters of integrated semiconductor circuits from the test patterns used for the more conventional testing of the DC parameters of such circuits. The AC parameters include such factors as rise time, fall time and circuit delays. Starting with a DC pattern known to be sufficient for the DC testing of the circuit to be tested, each increment of the DC pattern which comprises a plurality of parallel bilevel signals is applied to a corresponding plurality of input points in a standard of the circuit, preferably computer simulated. The resulting output is sensed at output points in the circuit standard. Then, one by one, the input signals in the applied increment are changed while the remainder of the signals are maintained at their original levels. When a change in one of the signals produces a corresponding change in the output, this is noted as path for AC testing. Then, there is stored as the first AC increment, a signal pattern wherein all the signals in the increments are maintained at their original levels except the input producing the change in output, which is stored as a pulsed signal. The procedure is repeated for a plurality of signals in the increment and for a plurality of remaining increments in the DC pattern until an AC signal pattern is developed in which all the input points in the circuit standard are pulsed at least once.

The impulse electric strength of polythene as a function of voltage rise time

Abstract: The electric strength of polythene has been measured using impulse voltages of differing rise times. The mean value of electric strength increases from 5·6 MV cm−1 for a voltage rise time of 60 μs to 6·6 mV cm−1 when the voltage rise time is 80 μs. The dc strength is 6·4 mV cm−1. The change in electric strength could be due to an internal polarization which reaches its final value in about 80 μs.

Pulse Reflection in Transmission Lines

Abstract: A simple theory based on linear approximation of the transient waveform and on the superposition theorem permits the prediction of waveforms and amplitude of the ripple voltage at the receiving end of a line which transmits pulses with finite rise time and which is mismatched at both ends. The influence of every connection in a digital system can be determined in this way.

Noise discriminating circuitry and method for electronic particle study apparatus

Abstract: By discriminating against signal rise time, i.e., the duration of the leading edge of a signal, noise signals can be excluded from data transmisson wherein the data pulses normally have slower rise times, even though both noise and data pulses exceed low threshold settings. When the subject discrimination is employed in the environment of a Coulter particle analyzing apparatus, the minimum rise time of data pulses derived from monitored particles is a known value; therefore, all signals having faster rise time can be discriminated against. The discriminator can comprise a source of clock pulses and a simple binary counter by use of which the rise time of each signal is compared with a preset time or count value. All signals having a rise time greater than the preset value causes the discriminator to enable an output gate which passes the original signal to subsequent processing and analyzing circuits for particle analysis.

A simple mechanically operated subnanosecond rise-time generator for pulses up to 100 kV

Abstract: A mechanically triggered generator capable of delivering pulses up to 100 kV with subnanosecond rise-times in a coaxial system is described and oscillograms of typical pulses obtained with this generator are given. The pulses are generated by switching a spark gap, but it has been found that the second sharpening gap which has been used in previous switches employing this technique is not necessary with this arrangement. The design and results of a resistance divider, used to attenuate these pulses, is included.

A Sweat Sensor for Qualitative Measurements

Abstract: : To study objectively the sweat response during motion sickness, a need existed for a small sweat-sensing device with a short latency of response, a fast response time, and the ability to follow the time course of the sweat response. The design and function of a sweat-sensing device for continuous monitoring of the sweat response are described. A lithium chloride-aluminum chloride sensing element, which changes resistance depending on the uptake or release of moisture, is used in this sensor. The sensing element is enclosed in a housing that is designed to circulate air from the skin surface to the sensing element. Air is supplied from a compressed-air cylinder and is controlled with a needle valve flowmeter assembly. With an air-flow rate of 15 cc/min and in response to a step change in moisture content on the skin surface, the sensor has a latency of 1.5 seconds and a rise time to reach 90 percent of the saturation level of about 28 seconds. A major disadvantage of the sensor is that with heavy sweat rates, the sensing element saturates, resulting in relatively long 'drying out' times. This can be partially offset by using higher air-flow rates, but at the expense of reduced sensitivity. The application of this sensor has shown that it is capable of responding to the cyclic sweat activity commonly seen when skin-resistance measurement techniques are used to monitor the sweat response. (Author)

Time Domain Measurement of Microwave Absorbers

Abstract: : This report describes a prototype time domain metrology system built under contract with the Air Force which could significantly reduce the time required to measure the properties of radar absorbing materials used on aircraft and missiles. During the development of such materials, many measurements are required of dielectric constant and permeability at different microwave frequencies, and by conventional means these can become very tedious. A system has been developed and delivered to the Air Force Avionics Laboratory, WPAFB, which generates subnanosecond rise time pulses, and measures the transient response of samples of the RAM material to these pulses.

Constant current pull-up circuit for a mos memory driver

Abstract: An improved driver circuit for MOS (metal oxide semiconductor) memory device including means such as constant current switch means selectively activated to supply a constant current to the MOS input during pull-up so as to decrease the pull-up current rise time.

Cryostat for annealing spectra measurements with short rise time to the annealing temperature

Abstract: A simple cryostat for annealing spectra measurements in the temperature range 78 to 700 °K is described and its specifications are given. The rise time at the annealing temperature is chosen equal to 1.5 minutes, giving thus, a practically square shape of the temperature pulse. An analogue valve regulates automatically a stream of cold nitrogen gas and maintains the temperature of the samples constant within ±0.05 °C. The rise time varies from 1 min, or even less, to about 7 min, when there is no control of temperature through the cold gas.

The effect of rise time on vibrotactile thresholds

Abstract: Thresholds of detectability were determined for vibration over the thenar eminences of six Ss at frequencies of 25 and 250 Hz as a function of the rise times of the envelopes of sinusoidal bursts. The results showed no effect over rise times ranging from 16 microsec to 160 msec, indicating that for long (1,000 msec) sinusoidal bursts the rise time is not an important parameter in the determination of vibrotactile thresholds.

Delay pickoff circuit

Abstract: A delay pickoff circuit initiates the generation of the ramp voltage of a delayed sweep generator of an oscilloscope in response to a comparison of an adjustable voltage from a delay time multiplier in a voltage comparator with the ramp voltage of a delaying sweep generator. The circuit utilizes a delaying sweep start gate voltage, which initiates the generation of the ramp voltage of the delaying sweep generator, to cause starting of the delayed sweep generator with less time delay after the start of the delaying sweep generator than is possible in prior circuits. This delaying sweep start gate voltage is employed to supply current to a tunnel diode which causes the tunnel diode to change from its low to high voltage state to thereby cause production of a delayed sweep start gate voltage when this operation of the tunnel diodes is enabled by a signal from the comparator as a result of setting the delay time multiplier at its zero delay setting. Current derived from the delaying sweep start voltage also conditions the tunnel diode for a similar change as a result of a signal from the comparator produced by a voltage comparison when the multiplier is set for substantially greater delays. A voltage derived from the delaying sweep start gate voltage and having a lesser rise time than the delaying sweep start gate voltage is employed to supply a part of this current to the tunnel diode in order to smooth the transition between these two conditions of operation of the tunnel diode.