Owen B. Laug

A custom integrated circuit comparator for high-performance sampling applications

The design and performance of an application specific integrated circuit (ASIC) comparator that has been optimized for equivalent-time waveform sampling applications is reported. The comparator, which has been fabricated with an 8.5-GHz f/sub T/, bipolar silicon process, features a bandwidth of >2 GHz, a settling-time accuracy of 0.1% in 2 ns, and almost total elimination of thermal tails in the settling response. The design has eliminated thermal effects, common in other comparators, than can cause errors and affect the voltage settling time. The comparator can be used in a sampling system for both frequency domain measurements, e.g., wideband RMS voltage measurements, and high accuracy time domain pulse measurements.<<ETX>>

A wideband sampling voltmeter

A high accuracy sampling voltmeter, designed to span the frequency range of 10 Hz to 200 MHz, is described. The instrument operates autonomously, at a measurement update rate of at least one per second. A novel quasi-equivalent time sampling process is used, with a custom strobed comparator as the sampling device and decision element. The architecture and control are presented, along with the time-base design principles. Major error sources associated with the time-base are also discussed.

Digitally synthesized power calibration source

A digitally synthesized source of “phantom” power for calibrating electrical power and energy meters is described. Independent sources of voltage, current, and phase angle are programmable between 0 and 240 V, 0 and 5 A, and 0 and 360 deg, respectively. The accuracy of the active and reactive power is estimated to be within ±100 ppm of the full-scale apparent power (volt-amperes).

A Wide-Band Transconductance Amplifier for Current Calibrations

A wide-band transconductance amplifier for current calibrations is described. The amplifier will deliver a ground-referenced constant current of 5 A rms from dc to over 100 kHz. Its stable magnitude and phase permit it to be used in precise power calibration systems to provide the current component of a phantom power source. The amplifier also provides a ground-referenced voltage output of 1 V/A for monitoring the magnitude and phase of the output current.

A high-current, very-wide-band transconductance amplifier

A novel design approach for a high-current, very-wide-band transconductance amplifier is described. The approach is based on paralleling the input and output of complementary unipolar current-mirror cells. Each cell has a fixed current gain determined by the ratio of two resistors. A differential input voltage-to-current circuit drives the cell array. The design avoids the need for a single low-resistance current-sensing resistor and the attendant problems inherent in such resistors. A prototype of the cell-based transconductance amplifier was implemented with ten positive and ten negative current cells to gain some experimental familiarity with the approach and provide verification of computer simulation results. The prototype transconductance amplifier is DC coupled, has a 3-dB bandwidth of about 750 kHz, and can deliver up to 35 A RMS (root mean square) at 100 kHz with an output voltage of 5 V RMS. Other important characteristics such as output-load regulation and DC offsets are discussed.<<ETX>>

Drift tubes for characterizing atmospheric ion mobility spectra using ac, ac‐pulse, and pulse time‐of‐flight measurement techniques

Two drift tubes constructed of insulating cylinders with conductive guard rings on the inside walls are examined to determine their suitability for measuring ion mobility spectra at atmospheric pressure. One drift tube is of the pulse time‐of‐flight (TOF) type with adjustable drift distance, and the other is an ac‐TOF drift tube similar in principle to devices reported by Tyndall and Powell [Proc. R. Soc. A 129, 162 (1930)] and Van de Graaff [Philos. Mag. 6, 210 (1928)]. The latter drift tube is evaluated using sinusoidal and alternating‐polarity pulse‐voltage waveforms for gating the shutters. Methods for determining the drift velocity of an ion from theoretical fits of the TOF spectrum are described for drift tubes of fixed length exhibiting ‘‘end effects.’’ Mobility values with uncertainties less than ±1% can be obtained with the pulse‐TOF drift tube. Comparable results are obtained with the ac drift tube if an alternating‐polarity pulse‐voltage waveform is used for gating the shutter.

A precision power amplifier for power/energy calibration applications

A precision power amplifier for use in power/energy calibration applications is described. The amplifier was primarily designed to boost the output amplitude of a digital generator to provide the nominal 120- or 240-rms voltage component of a “phantom” calibration power source. The amplifier has a fixed gain of 40 and can provide a maximum output voltage swing of 970 V peak-to-peak or 340-V rms at 100-mA rms. The bandwidth is from dc to 150 kHz and at 60 Hz the observed no-load short-term amplitude and phase instabilities are ±5 ppm and ±5 μrad, respectively. The amplifier design uses high-voltage N-channel MOSFETs in the output driver stage together with a unique circuit topology of opto-isolators between the low-level input stage and the high-level output stage.

Improved time-base for waveform parameter estimation

An improved gated-oscillator time-base and associated auto-calibration algorithm for use in a high-accuracy sampling waveform acquisition system are described. The time-base architecture consists of a stable 100 MHz gated-oscillator, 24-bit counter chain, and a clock period interpolator. The nominal, uncorrected linearity of the time-base is approximately /spl forall/30 ps. By using an iterative, sine-fit based algorithm, the linearity has been improved to </spl forall/5 ps. Details of the performance and major sources of error of the time-base and correction algorithm in an equivalent time sampling system are also discussed.

A 600 V AC Voltage Amplifier for Power Measurements

A voltage amplifier composed of three cascaded -10:1 gain sections has been developed to extend the voltage range of primary electric power calibrations from 120 to 600 V over the 50-400-Hz frequency range. The gain and phase errors of each amplifier section are continuously measured and corrected in situ using a permuting impedance measurement technique. The amplifier design approach, measurement principles, and initial performance results are presented.

Project fist: Fault isolation by semiautomatic techniques: Part I — Basic concept and techniques

FIST has been developed for the maintenance of modularized, noncomputer, electronic equipment. Tests are dynamic, meaningful, rapid, and can be performed by an unskilled technician. System flexibility and concepts may well revolutionize maintenance methods for both military and industrial equipment The method of fault isolation by semiautomatic techniques developed at the National Bureau of Standards, to which the acronym FIST has been applied, is a diagnostic tool for rapidly isolating faults in modularized, noncomputer-type electronic equipment without removing the modules from the prime equipment. The method is simple and flexible and is orders of magnitude faster than trouble shooting with manual test equipment.