Showing papers in "IEEE Transactions on Instrumentation and Measurement in 1975"
TL;DR: The Fraunhofer line discriminator Mark II (FLD-II) is an airborne photometric instrument for the remote measurement of solar-stimulated luminescence as discussed by the authors.
Abstract: The Fraunhofer line discriminator Mark II (FLD-II) is an airborne photometric instrument for the remote measurement, on a precise and quantitative scale, of solar-stimulated luminescence. The luminescence may originate in such diverse sources as oil spills and chemical pollutants, the chlorophyll of normal or stressed vegetation, and fluorescent tracer dyes used to study current flow and dispersion in large bodies of water. Work now in progress by the U. S. Geological Survey expresses the concentrations of various fluorescent substances in terms of equivalent concentrations of the tracer dye, rhodamine WT, in water that the FLD-II can reliably measure down to levels of 0.1 part per billion (1 part in 1010). Detailed calculations show that this is within a factor of about 21/2 to 5 of theoretical, photon-limited performance. The instrument measures luminescence in a scene by quantitative distinction between reflected sunlight, which is "coded" by Fraunhofer absorption bands, and luminescence, which is not. Narrow-band optical filters provide in-band and out-of-band light samples from the scene and from pure sunlight to a photomultiplier tube. Digital conversion and computation render a reading of the fluorescence coefficient.
164 citations
TL;DR: In this paper, a new technique is presented which makes it possible to measure the inherent short-term stability of quartz crystal resonators in a passive circuit, and it is shown that with this improved shortterm stability it should be feasible to multiply a crystal controlled source to 1 THz and obtain a linewidth of less than 1 Hz.
Abstract: A new technique is presented which makes it possible to measure the inherent short-term stability of quartz crystal resonators in a passive circuit. Comparisons with stability measurements made on crystal controlled oscillators indicate that noise in the electronics of the oscillators very seriously degrades the inherent stability of the quartz resonators for times less than 1 s. A simple model appears to describe the noise mechanism in crystal controlled oscillators and points the way to design changes which should improve their short-term stability by two orders of magnitude. Calculations are outlined which show that with this improved short-term stability it should be feasible to multiply a crystal controlled source to 1 THz and obtain a linewidth of less than 1 Hz. In many cases, this improved short-term stability should also permit a factor of 100 reduction in the length of time necessary to achieve a given level of accuracy in frequency measurements.
117 citations
TL;DR: In this paper, the effect of frequency multiplication on the RF spectrum of an oscillator has been studied and a simplified theory is developed and shown to reproduce the experimental results for the relative power in the carrier and noise pedestal, and the shape and the width of the carrier.
Abstract: A novel experimental technique is introduced and used to measure the effect of frequency multiplication on the RF spectrum of an oscillator. This technique makes it possible to produce the RF spectrum at X band?where measurements are relatively straightforward?that would have been produced by frequency multiplication of the 5-MHz source to any frequency from 9.2 GHz to 100 THz (1014 Hz). A simplified theory is developed and shown to reproduce the experimental results for the relative power in the carrier and noise pedestal, and the shape and the width of the carrier and noise pedestal, to within the measurement uncertainty of 2 or 3 dB, from 5 MHz to 10 THz. The calculations are easily made using analytical techniques from the measurement of the spectral density of phase fluctuations of the source, the effective input spectrum density and the bandwidth of the multiplier chain, and the frequency multiplication factor. It is shown that present 5-MHz-crystal-controlled oscillators are useful as a precision source to ~500 GHz. Suggestions for extending their range to ~100 THz are made.
84 citations
TL;DR: An impedance bridge for highvoltage capacitance and related measurements to an accuracy of 1 ppm is described and the background research and development which made it possible is documented in this paper, where the bridge is of the transformer-ratioarm type, the principal components of which are a comparator and several two-stage transformers.
Abstract: An impedance bridge for high-voltage capacitance and related measurements to an accuracy of 1 ppm is described and the background research and development which made it possible is documented. The bridge is of the transformer-ratioarm type, the principal components of which are a comparator and several two-stage transformers. The bridge can be used to measure capacitance ratios over a range from 1/1 to 107/1 with a resolution between 0.1 and 0.25 ppm. The highest accuracies are obtained at the principal power frequencies of 50-60 Hz, but the bridge is usable up to 400 Hz. The factors which limited the accuracy of previously developed bridges of this type were reexamined and their influence reduced. Two independent methods were developed for the calibration of the bridge.
48 citations
TL;DR: In this article, a principle for absolute voltage division is presented, which does not depend on the values of its elements but depends exclusively on the configuration of the divider network, hence, calibration is not necessary and not even possible.
Abstract: In this paper, a principle for absolute voltage division is presented. The division ratio of a voltage divider on this principle does not depend on the values of its elements but depends exclusively on the configuration of the divider network. Hence, calibration is not necessary and not even possible. Absolute voltage division is obtained by cyclically shifting the network elements along all positions in the divider network. Each position is maintained for an equally long time interval. The average output voltage of such a dynamic divider is identical to that of a static divider with the same network configuration but composed of elements which all have the same value. To verify the principle in practice, a digitally controlled resistive voltage divider has been built. It has been realized with easily available electronic components, such as carbon resistors with ± 5-percent tolerance, junction field-effect transistors as electronic switches and digital integrated circuits for the generation of the switch drive signals. The inaccuracy of this divider is less than 5 ×10-6 and the temperature coefficient of the division ratio is less than 5 × 10-8/°C from 0°C to 40°C. It is expected that the performance, of this prototype can be improved.
41 citations
TL;DR: In this article, a lumped capacitance method for measurement of the permittivity and conductivity of materials in the radio and microwave frequency ranges is presented, and the analysis of the method applicable in both frequency and time domains is given for materials having low frequency conductivity or Debye dispersion.
Abstract: Further discussion of a lumped capacitance method for measurement of the permittivity and conductivity of materials in the radio and microwave frequency ranges is presented. The analysis of the method applicable in both frequency and time domains is given for materials having low frequency conductivity or Debye dispersion.
25 citations
TL;DR: In this paper, a non-structive microwave cavity approach for measuring complex permittivities of materials in sheet form is described, where the resonant cavity is a section of a rectangular waveguide terminated by a thin rigid and large flange containing a small rectangular iris opening and the iris is placed in firm contact with one side of the dielectric sample while the other side is backed with a highly conducting plate.
Abstract: A nondestructive microwave cavity approach for measuring complex permittivities of materials in sheet form is described. The resonant cavity is a section of a rectangular waveguide terminated by a thin rigid and large flange containing a small rectangular iris opening. The iris is placed in firm contact with one side of the dielectric sample while the other side is backed with a highly conducting plate. Variations of the cavity resonant frequency and Q-factor caused by the dielectric can be related to its complex permittivity through the consideration of equivalent admittance of this open-ended dielectricloaded aperture at resonance. Experimental determination of aperture admittance of a loaded iris is made and the results compared with theoretical calculations. The validity of this technique is confirmed by evaluating the resonant cavity characteristics by loading it with dielectrics of known permittivities and comparing the results with theoretical results. The permittivity of a lossy dielectric slab is measured and the value obtained by this method is compared with those found by other techniques. In all these cases the agreement between theory and measurements is satisfactory. Utility of this technique in evaluating the local inhomogeneities of permittivity of sheets is demonstrated. Measurement errors and limitations of this technique are pointed out.
22 citations
TL;DR: In this paper, a method for the determination of absolute changes in capacitance and absolute values of conductance, as functions of frequency, is presented for the use of two variable parallel-plate capacitors, and requires the measurement of relative capacitance values over a range of frequencies and at a minimum of two different electrode spacings.
Abstract: Electrode surface effects in parallel-plate capacitors lead to a variation in capacitance and conductance with frequency. A method is presented for the determination of absolute changes in capacitance and absolute values of conductance, as functions of frequency. The method involves the use of two variable parallel-plate capacitors, and requires the measurement of relative capacitance and conductance values over a range of frequencies and at a minimum of two different electrode spacings. A capacitor cell, incorporating two variable capacitor sections is described. The cell is designed for use in the investigation of the frequency characteristics of a range of electrode surfaces. Two current transformer ratio-arm bridges are used to perform the relative admittance measurements. The bridges are compensated for capacitance loading, and together cover the frequency range 11 Hz-52 kHz. Measurement precision is a few parts in 108 for each admittance component. Details of the bridges and measurement techniques are discussed and corrections for mechanical resonance effects and lead impedances are considered. Results are given for rhodium plated and plain brass electrodes under vacuum. Over the full frequency range the fractional capacitance change for rhodium, when referred to a 1-mm electrode spacing, is <4 × 10-7. Tan ? is < 1.5 × 10-7. Oil films and organic contaminants on electrode surfaces are thought to be the most likely sources of frequency dependence.
22 citations
TL;DR: In this article, a procedure for fitting a large (>3) number of arbitrarily chosen experimental data points to a fractional linear transformation on a complex plane is developed, and the transformation coefficients as well as their standard deviations are computed directly from the set of measured impedances or reflection coefficients.
Abstract: A procedure is developed for fitting a large (>3) number of arbitrarily chosen experimental data points to a fractional linear transformation on a complex plane. The transformation coefficients as well as their standard deviations are computed directly from the set of measured impedances or reflection coefficients, without any resort to graphical procedures. The procedure can be applied to linear reciprocal two-ports.
19 citations
TL;DR: In this paper, a square-wave generator, which employs an operational amplifier and is easy in construction, is considered for converting temperature to frequency so that the advantages of digital measurement of any physical quantity are utilized.
Abstract: In this article a square-wave generator, which employs an operational amplifier and is easy in construction, is considered for converting temperature to frequency so that the advantages of digital measurement of any physical quantity are utilized. A new procedure is suggested for obtaining linearity over a wide range of temperature for a specified value of deviation. Theoretical deviation curves have been obtained to show that the new procedure gives a wide range of temperature.
18 citations
TL;DR: An automatic error plotting system for analog-to-digital converters (ADC's) which measures the static errors of the device under test at every quantization band edge (QBE) and displays them in graphical form and shows the ability of the system to display common types of ADC errors and to display error signatures that often point to specific ADC problems.
Abstract: This paper describes an automatic error plotting system for analog-to-digital converters (ADC's) which measures the static errors of the device under test at every quantization band edge (QBE) and displays them in graphical form. A quantization band edge is defined as any ADC input voltage which produces two adjacent output codes, each with 50-percent probability. The error of the ADC is then defined as the difference between the actual and nominal values of a QBE. A feedback loop which seeks each QBE is central to the system. Sample plots show the ability of the system to display common types of ADC errors and to display error signatures that often point to specific ADC problems. Resolution, accuracy, and (to a large extent) speed of the system depend on the digital voltmeter chosen as a standard. In a typical case, a 2000 point plot can be made in two minutes with a resolution and accuracy exceeding the weight of the ADC's least significant bit by an order of magnitude.
TL;DR: In this paper, the temperature and pressure coefficients of three buffer gases, N2, Ar, Kr, commonly used in passive Rb57 frequency standards have been accurately determined and techniques for filling cells reproducibly, are described.
Abstract: The temperature and pressure coefficients of three buffer gases, N2, Ar, Kr, commonly used in passive Rb57 frequency standards have been accurately determined. Techniques for filling cells reproducibly, are described. From the results obtained, calculations are made on the expected characteristics of gas mixtures. Graphs are given which can be used to select the proper buffer gas mixture and pressure to obtain specially required frequency shift and temperature coefficient in a given cell.
TL;DR: Two methods of accumulating, analyzing, and presenting in real time the data generated by a Kerr system in response to a high-voltage impulse are presented.
Abstract: The purpose of this paper is to present two methods of accumulating, analyzing, and presenting in real time the data generated by a Kerr system in response to a high-voltage impulse. These methods provide immediate information concerning selected electrical parameters in a form which is easily interpretable by most personnel. The first method uses an electronic counter to determine the number of optical transmittance maxima, i.e., light pulses, duritg the high-voltage impulse. From this count, the peak value of impulse can be calculated. The second method, which can be more accurate and does provide information concerning waveshape, uses a digital recorder to store the output waveform from the Kerr system. A computer is then used to reconstruct the voltage impulse and to determine such parameters as the peak value and risetime of the impulse.
TL;DR: In this article, a new technique to linearize the temperature-frequency relationship of an astable multivibrator using one thermistor is proposed, and the center frequency can be adjusted at any set frequency by an adjustable resistance.
Abstract: A new technique to linearize the temperature-frequency relationship of an astable multivibrator using one thermistor is proposed. The center frequency can be adjusted at any set frequency by an adjustable resistance. Furthermore, the oscillation frequency is not affected by the change of supply voltage.
TL;DR: In this article, a description of a compact Rb87 maser approximately 20 cm in diameter and 30 cm in length is given and the features of the principal components are discussed.
Abstract: A description of a compact Rb87 maser approximately 20 cm in diameter and 30 cm in length is given and the features of the principal components are discussed. The fractional frequency fluctuations (Allan variance) are less than 5 × 10-13 for averaging times between 1 and 103 s. The effects of various parameters on the maser frequency are investigated experimentally and compared to theoretical predictions obtained from the maser frequency equation.
TL;DR: The Walsh expansion of a periodic sinusoid is an infinite series; however, if one synthesizes a sinusoidal from a truncated Walsh expansion, the result is a stepped approximation to the sinusoids that has minimum mean-square error.
Abstract: The Walsh expansion of a periodic sinusoid is an infinite series; however, if one synthesizes a sinusoid from a truncated Walsh expansion, the result is a stepped approximation to the sinusoid that has minimum mean-square error. The first 2m nonzero terms in the Walsh expansion yield a wave that has 2m steps per quarter-cycle. A notable feature of this wave is the wide separation between its harmonic pairs. For example, eight nonzero Walsh terms yield a wave whose only nonzero harmonics are the 31st and 33rd, the 63rd and 65th, etc., harmonic magnitudes being inversely proportional to frequency. Waves of this type are readily synthesized using a synchronous Walsh array generator with true and complement outputs, a level converter system, and a summing circuit.
TL;DR: In this article, three modifications of time-division multipliers have been investigated with respect to their response to ac and dc input quantities, and the results were presented in form of graphs and tables.
Abstract: Three modifications of time-division multipliers have been investigated with respect to their response to ac and dc input quantities. These investigations were part of the development of an electronic ac-dc power comparator and were carried out by aid of a computer (Siemens type 4004). The calculations take into account different values of power factors, sample rates, amplitudes and different signal phases with respect to the first sample pulse. Results are presented in form of graphs and tables.
TL;DR: In this paper, the influence of the parallel capacitance of a quartz-crystal resonator on the amplitude-frequency coupling and particularly on the internal noise spectra of the oscillator working at the series resonance is described.
Abstract: This paper describes the influence of the parallel capacitance of a quartz-crystal resonator on the amplitude-frequency coupling and particularly on the internal noise spectra of the oscillator working at the series resonance. A theoretical analysis which is a first order perturbation method is used. It is shown that the parallel capacitance of the quartz-crystal resonator increases the amplitude-frequency coupling and drastically modifies both amplitude and phase spectra of the internal noise. The 1/f2 phase spectrum of the internal thermal noise is transformed into a white phase spectrum for noise component frequencies greater than f0 + f? or less than f0 - f?, where f0 is the resonator series resonant frequency and f?, the difference between antiresonant and resonant frequencies of the quartz crystal. A "noise quieting" phenomenon appears when the noise component frequencies are in the vicinity of the antiresonant frequency fp. A good agreement between theoretical and experimental results for different values of the parallel-capacitance proves the validity of the mathematical model.
TL;DR: In this article, the 2.66 K value is in good agreement with the currently accepted value of 2.8 K. The two largest error sources were due to uncertainties in the calibration of the liquid helium cooled termination and the antenna transmission line.
Abstract: Cosmic background noise temperature measurements which were made at 13.05-cm wavelength (2297 MHz) resulted in an experimental value of [266 ± 0.77 (3?)] K. The two largest error sources were due to uncertainties in the calibration of the liquid helium cooled termination and the antenna transmission line. The 2.66 K value is in good agreement with the currently accepted value of 2.8 K. Measurements were made at 2297-MHz space communications frequency because cosmic background noise is an important consideration in the calculations of expected signal-to-noise ratios for spacecraft and ground receiving systems.
TL;DR: In this article, a generalized analysis of the source mismatch effects on noise measurements, which considers the dependence of the noise performance of the two-port on the input admittance, is presented.
Abstract: A noticeable source mismatch occurs in measurements of noise parameters of a linear two-port, since an admittance-transformer network between the source and the two-port must be inserted. A generalized analysis of the source mismatch effects on noise measurements, which considers the dependence of the noise performance of the two-port on the input admittance, is presented here. On this basis, two types of noise generators are considered and compared with each other.
TL;DR: A system has been developed for ultra-high-speed digital recording and analysis of transient phenomena that enables one to look back in time, recording signals that occur prior to single events which have statistical uncertainties of occurrence, such as lightning or breakdown phenomena.
Abstract: A system has been developed for ultra-high-speed digital recording and analysis of transient phenomena. It enables one to look back in time, recording signals that occur prior to single events which have statistical uncertainties of occurrence, such as lightning or breakdown phenomena. The system as installed is playing an essential role in studying " cause-effect" relationships through the acquisition and analysis of data. Data are received in an asynchronous fashion in real time and stored in a cartridge disk through Transient Recorders (Biomation Model 8100) and minicomputer (Melcom-70, Japan). The system is time-shared and digital-controlled by multiple users from remote consoles located at nine test stations. The stored data are retrieved and analyzed with highest "time availability" priority to get processed information through correlation, statistical analysis or various computer-aided simulations. Special precautions have been taken against high energy electromagnetic noise fields, such as grounding, shielding, etc., in order to attain noise-proof operation. Principles of operation, major components, and examples of the application of the system are presented.
TL;DR: In this article, the dual-slope conversion is used to enable multiplication, exponential and logarithmic conversion, determination of nth roots, and solution of polynomial equations to be performed during the conversion cycle.
Abstract: New methods for precise linear and nonlinear A/D, A/A, and D/A transformations, based on the principle of the dual-slope conversion are proposed. These methods enable multiplication, exponential and logarithmic conversion, determination of nth roots, and the solution of polynomial equations to be performed during the conversion cycle.
TL;DR: In this article, a dc-current source with selectable ratios in the range between 10 mA and 5 A was developed for high-precision electrical measurements, specially on superconducting circuits.
Abstract: For applications in the field of high-precision electrical measurements, specially on superconducting circuits, a dc-current source has been developed, which supplies two dc currents with selectable ratios in the range between 10 mA and 5 A. The performance of the instrument relies on the combination of conventional dc-current comparators with low ripple sampling detectors and ironless cryogenic current comparators with a SQUID as zero detector. Thus the current ratio is stabilized to 1 X 10-9 of its value.
TL;DR: In this paper, a differential method to measure the equivalent series inductance (ESL) and equivalent series resistance (ESR) of energy discharge capacitors is described and compared with other available methods.
Abstract: A differential method to measure, simply and accurately, the equivalent series inductance (ESL) and the equivalent series resistance (ESR) of energy discharge capacitors is described and compared with other available methods. The differential method measures the ESL over a wide range of inductance, including extremely low inductance values, without elaborate equipment or intricate data interpretation. The differential method also determines the ESR of fast energy capacitors at frequencies approaching the capacitor self-resonant frequency.
TL;DR: In this paper, the authors used the unique property of the quartz resonator in the design of the oscillator with the result of substantial improvement in oscillator short-term frequency stability.
Abstract: For years, engineers and scientists have been plagued by an extremely undesirable property of the quartz crystal unit-its significant frequency shift as a function of drive level for drive levels in excess of 10 to 100 ?W. This fact was reported by Hammond [1]. As a result, all precision and moderate precision quartz oscillators have been operated at low drive in an effort to avoid the phenomena. The author has discovered, however, that this unique property of the quartz resonator can be effectively utilized in the design of the quartz oscillator with the result of substantial improvement in oscillator short-term frequency stability. Futhermore, since the crystal frequency-drive characteristic is repeatable, maintenance of moderately high crystal drive in the oscillator circuit will not result in long-term frequency instability in excess of that required for the majority of radar and communication systems [2].
TL;DR: In this paper, a simple algorithm is developed which yields the velocity, as a function of time, of an object moving against a complicated background, which relies on monitoring magnitude and phase of two prominent spatial Fourier components.
Abstract: The passive detection of velocities of objects moving transverse to the optical viewing axis is discussed from the standpoint of the spatial Fourier transform of the image. A simple algorithm is developed which yields the velocity, as a function of time, of an object moving against a complicated background. This algorithm relies on monitoring magnitude and phase of two prominent spatial Fourier components. Measurement of the Fourier components is most simply accomplished with the direct electronic Fourier transform (DEFT) sensor. This device employs coupling between the image intensity, surface acoustic waves, and electron current in a CdS film to decompose the image into Fourier components. Experimental results show strong confirmation between theory and experiment. The paper concludes with a brief comparison of the DEFT implementation versus other systems in terms of speed, sensitivity, and cost.
TL;DR: In this paper, an open-ended microwave cavity is used to measure residual water content or bound water content in nonconductive fluids transported in circular pipes, where the sensor consists of a section of a circular waveguide lined with a solid dielectric inserted in series with the piping system transporting the test fluid.
Abstract: This paper presents a novel application of open-ended microwave cavities for monitoring residual water content or bound water content in nonconductive fluids transported in circular pipes. The sensor consists of a section of a circular waveguide lined with a solid dielectric inserted in series with the piping system transporting the test fluid. At the selected frequency of operation, the end waveguides formed by the piping system operate below cutoff, while the sensor forms a resonant cavity. The resonant frequency of the cavity, which is a measure of the water content in the test fluid, is monitored automatically by an electronic system.
TL;DR: In this article, a unique method for the continuous measurement of electric-arc duration is presented, which is possible to know the distribution of arc durations at any instance of time and, at the same time, the integration of arc duration has become much more convenient and less time consuming than any other existing methods.
Abstract: A unique method for the continuous measurement of electric-arc duration is presented. By using the method, it is possible to know the distribution of arc durations at any instance of time and, at the same time, the integration of arc durations has become much more convenient and less time consuming than any other existing methods. It has also been found that the total integrated-arc durations bear a linear relationship with the number of operations on a log-log scale.
TL;DR: In this paper, the use of optical and electromagnetic current transformers for protection and measurement in EHV transmission systems is outlined along with salient specifications imposed by diversification of present-day applications.
Abstract: The use of optical and electromagnetic current transformers for protection and measurement in EHV transmission systems is outlined along with salient specifications imposed by diversification of present-day applications. Basic principles of operation and typical applications of optical and electromagnetic current transformers are presented.
TL;DR: In this paper, a new method for measuring the complex reflection coefficient in a measurement system with a slotted line and homodyne detector is presented, which involves the investigation of the change of phase angle of wave voltage along the waveguide terminated with the element under test.
Abstract: A new method for measuring the complex reflection coefficient in a measurement system with a slotted line and homodyne detector is presented. The measurement involves the investigation of the change of phase angle of wave voltage along the waveguide terminated with the element under test. The principle of measurement and X-band measurement system consisting of waveguide elements are described. The signal fed to the homodyne detector is subject to the rectangular phase modulation which facilitates the construction of the modulator and increases the accuracy of phase determination. The phase shifter used in the system includes a slotted line. The reduction of the influence of residual reflections on the phase shift determination is described. Even with standard waveguide elements the measuring accuracy of amplitude reflection coefficient is found to be approximately 10-3.