Showing papers in "IEEE Transactions on Instrumentation and Measurement in 1979"
TL;DR: In this article, interpolated fast Fourier transform (FFT) algorithms are used for multi-parameter measurements upon periodic signals, such as fundamental frequency, phase, and amplitude, with enhanced accuracy compared to existing algorithms.
Abstract: By use of an interpolated fast-Fourier-transform (FFT) algorithms are developed for multiparameter measurements upon periodic signals. Eight pertinent measurements, such as fundamental frequency, phase, and amplitude, are made with enhanced accuracy compared to existing algorithms, including tapered-window-FFT algorithms. For the more general case of nonharmonic multitone signals also the method is shown to yield exact amplitudes and phases if the tone frequencies are known beforehand. These measurements are useful in a variety of applications ranging from analog testing of printed-circuit boards to measurement of Doppler signals in radar detection.
421 citations
TL;DR: In this article, the effect of dead time on the precision of the time domain measure of frequency stability, in the presence of a limited number of data, was investigated and the possibility to distinguish between white and flicker noises was pointed out.
Abstract: Expressions for the averaged two-sample variance as well as expressions for the uncertainty on its estimation are given, in cases where dead time is present between measurements. The effect of this dead time on the precision of the time domain measure of frequency stability, in the presence of a limited number of data, is specified. The possibility to distinguish between white and flicker noises is pointed out.
84 citations
TL;DR: A novel technique based on a special algorithm in which the capacitor array is used as a precision voltage divider is developed and a capacitor array tester consisting of both hardware and software has been built which executes this algorithm.
Abstract: The recent development of integrated circuit capacitor arrays and the growth of their applications have resulted in a need to perform precision testing as an aid to future design improvements. For reasons discussed in this paper, laboratory instruments such as capacitance bridges are not well-suited to this need. In order to test capacitor arrays accurately, a novel technique has been developed. It is based on a special algorithm in which the capacitor array is used as a precision voltage divider. A capacitor array tester consisting of both hardware and software has been built which executes this algorithm. This system has been used to perform measurements upon a large number (thousands) of NMOS and CMOS capacitor arrays. The standard deviation of this tester's measurement error is approximately 0.0009 percent of full scale (0.0088 LSB referenced to 10 bits). In contrast with manual testing with a capacitance bridge (requiring 10 min per array), the tester requires less than 5 s to fully test an array, mark the circuit and move to the next die position.
41 citations
TL;DR: In this article, a study of the transfer of frequency stability from an atomic reference to a quartz-crystal oscillator is presented, and the results obtained from numerical calculations are presented under the form of graphs.
Abstract: This paper presents a study of the transfer of frequency stability from an atomic reference to a quartz-crystal oscillator. The study is done for the cases of active and passive atomic frequency standards in which one makes use of a phase-lock loop and of a frequency-lock loop, respectively. The analysis is made in both the frequency and time domains and covers the cases of the hydrogen and rubidium masers and the passive cesium-and rubidium-frequency standards. The results obtained from numerical calculations are presented under the form of graphs. These results include the fractional frequency spectral density Sy(f) as a function of the Fourier frequency f, and the two sample variance ?2(?) as a function of ?, the sampling time.
37 citations
TL;DR: In this paper, a time-domain reflectometer (TDR) system was used to obtain data on the frequency dependence of the dielectric properties of a few agricultural materials.
Abstract: A time-domain reflectometer (TDR) system was used to obtain data on the frequency dependence of the dielectric properties of a few agricultural materials. Values for the complex relative permittivity in the frequency range from about 30 MHz to 1 or 2 GHz were obtained from the reflection coefficient, which was calculated from the ratio of the Fourier transforms of the incident and reflected waveforms from the dielectric sample in a coaxial line. With the TDR system, broad dielectric dispersion and absorption regions, similar to those found by frequency-domain measurements, were determined with significant reductions in time and effort.
34 citations
TL;DR: In this article, the authors discuss the use of time-domain reflectometer (TDR), a vector voltmeter, and a network analyzer for determining the complex permittivity or moisture content of bulky or film-like materials.
Abstract: Recent advances in VHF and UHF transmission line methods for determining either the complex permittivity or moisture content of bulky or film-like materials, or the thickness of film-like materials are discussed. These methods include TDR, CW phase, and |S21| transmission methods and employ a time-domain reflectometer (TDR), a vector voltmeter, and a network analyzer, respectively. Each technique involves monitoring the change of the transmission line parameters of a balanced open line, or of an unbalanced coaxial transmission line, when loaded with the material under test. Particular attention is given to the frequency range 10 to 1000 MHz and to broad-band methods. Experimental results are presented for several common materials, viz. concrete, asphalt, Plexiglas, moist paper, and moist soil.
31 citations
TL;DR: In this paper, a method for measuring the complex permittivity of biological liquids at microwave frequencies is presented; this method allows measurements to be made very quickly, using only very small amounts of material.
Abstract: A method for measuring the complex permittivity of biological liquids at microwave frequencies is presented. The calibration needs three reference materials; this method allows measurements to be made very quickly, using only very small amounts of material. Measurements were made on human erythrocytes, obtaining their inner conductivity using Fricke's equation, and on human sera of normal and sick individuals. Using an optimization technique, some parameters related to the water bound to the serum proteins were identified, showing differences possibly related to the presence of certain diseases.
29 citations
TL;DR: In this paper, an electrooptical measuring device has been developed for detecting blood spots in intact eggs based on the selective absorption of hemoglobin, with an accuracy and stability within 1 percent over a dynamic range of three decades of absolute egg transmittance values.
Abstract: An electrooptical measuring device has been developed for detecting blood spots in intact eggs based on the selective absorption of hemoglobin. The detection system performs a ratio measurement at two wavelengths with an accuracy and stability within 1 percent over a dynamic range of three decades of absolute egg transmittance values. Because of the very low transmittance level much care has been given to stray- and background-light suppression The detection results re substantially independent of electrooptical transfer vriations System design includes economical factors and is partly devoted to a 12 row conveyor belt system with a cycling time of 1 s. The system discriminating sensitivity in selective absorption can be adapted to the natural scatter in the spectral properties of eggs.
27 citations
TL;DR: In this paper, a monolithic operational amplifier is used as the main building block, and a modified current mirror is used to recover the signal current from the power supply leads of the amplifier.
Abstract: A technique for realizing a high-quality controlled current source is described. A monolithic operational amplifier is used as the main building block, and a modified current mirror is used to recover the signal current from the power supply leads of the amplifier. The proposed mirror exhibits low input resistance, which reduces errors due to the noninfinite power-supply rejection characteristics of the amplifier, and a current-splitting network allows the realization of output impedances in the range of tens of megohms using standard components. The entire circuit operates in a class-AB mode for high drive capability with low values of quiescent current. A simple application is included to show that a voltage amplifier can readily be constructed which exhibits a 3-dB gain-bandwidth product forty times larger than the gain-bandwidth product of the operational amplifier used. Detailed experimental results are included to verify predicted frequency response and gain characteristics.
26 citations
TL;DR: In this paper, an improved dual-slope analog-to-digital converter for measurements made with a pair of resistive or capacitive differential transducers is described, which can be contrasted with the conventional method in which the transducers are placed in a bridge, the bridge output is amplified, and the conversion is made.
Abstract: An improved dual-slope analog-to-digital converter for measurements made with a pair of resistive or capacitive differential transducers is described. The converter can be contrasted with the conventional method in which the transducers are placed in a bridge, the bridge output is amplified, and the conversion is made. In the new converter the transducers are part of the integrator. As a result, conversion of the signal to a time interval takes place at an earlier stage, eliminating the bridge and the amplifier. The method has the same advantages as the dual-slope method and several additional ones. The fractional change in the transducers is obtained as the ratio of the difference and sum of two time periods. As a result, the converter does not need an accurate voltage reference. In addition, errors due to offset in the integrating amplifier are eliminated.
25 citations
TL;DR: In this paper, very-long-baseline interferometry (VLBI) observations of several extragalactic radio sources were made sequentially in eight 360-kHz bands distributed between about 8.4 and 8.5 GHz with spacings designed to enable the group delay difference between the signals received at the two observatories from a given source to be estimated unambiguously, within an uncertainty of less than 1 ns set by receiver noise.
Abstract: Two hydrogen-maser clocks, one at the Haystack Observatory in Massachusetts and one at the National Radio Astronomy Observatory in West Virginia, were synchronized by means of very-long-baseline interferometry (VLBI) observations of several extragalactic radio sources on March 28, and again on September 23, 1977. Observations were made sequentially in eight 360-kHz bands distributed between about 8.4 and 8.5 GHz with spacings designed to enable the group-delay difference between the signals received at the two observatories from a given source to be estimated unambiguously, within an uncertainty of less than 1 ns set by receiver noise. The epoch and the rate differences between the observatories' clocks for each experiment were estimated by analysis of observations that spanned several hours. The application of corrections for the contributions to the delays of the antennas, feeds, receiver systems, and recorders, yielded absolute determinations of the clock epoch differences. During each experiment, portable cesium clocks were flown from the U.S. Naval Observatory in Washington, DC, to the observatories and back. The traveling-clock data, analyzed in each case after the VLBI synchronization had been completed, confirmed the VLBI results to within 18 and 14 us for the first and second experiments, respectively.
TL;DR: In this paper, the reciprocal time generator is used to produce a digital output proportional to the time elapsed between successive incoming pulses and the output of which is sampled and held at the end of each cycle.
Abstract: A basic instrument is described which produces a parallel digital output proportional to frequency once per cycle, i.e., instantaneously. This is achieved by means of a reciprocal time generator which continuously generates digitally the reciprocal of the time elapsed between successive incoming pulses and the output of which is sampled and held at the end of each cycle. The meter is a 12-bit instrument having an accuracy of ±1 count plus clock stability. An analog output and a digital readout can be readily obtained. The range of the instrument is from zero to fc × 2-12 Hz, where fc is the clock frequency in hertz. Thus the range can be varied by appropriate adjustment of fc. An additional circuit to provide an analog output proportional to rate of change of frequency, also on a cycle-to-cycle basis, is suggested.
TL;DR: An automated test set is described for characterizing the static performance of high resolution ADC's and DAC's with uncertainties of 2-4 ppm.
Abstract: An automated test set is described for characterizing the static performance of high resolution ADC's and DAC's. Measured parameters include gain, offset, linearity, and equivalent ADC input noise with uncertainties of 2-4 ppm. Measurements to full accuracy can be made at a rate up to 40/s. A 20-bit DAC serves as a comparison standard.
TL;DR: In this article, a 10 ppm four-terminal-pair audio-frequency impedance bridge is described, which can be operated either in an impedance mode, for self-inductance, mutual inductance, and resistanre measurements; or in an admittance mode for capacitance and conductance measurements.
Abstract: A wide range 10 ppm four-terminal-pair audiofrequency impedance bridge is described. The bridge can be operated either in an impedance mode, for self-inductance, mutual inductance, and resistanre measurements; or in an admittance mode for capacitance and conductance measurements. The frequency range for full aecuracy is 40 Hz to 2 kHz. Maintenance of the calibration of the bridge is facilitated by the use of transformer ratios to extend the range of a small number of precision components, and extensive use is made of electronic techniques to automate auxiliary balances.
TL;DR: The surface characteristic of a number of electrode materials including stainless steel, brass, brass whit various plated surfaces, aluminum, and anodized aluminum has been examined over a wide range of humidity as discussed by the authors.
Abstract: The surface characteristic of a number of electrode materials including stainless steel, brass, brass whit various plated surfaces, aluminum, and anodized aluminum has been examined over a wide range of humidity. The measurements of surface charcteristic, expressed in microradian millimeters, have an estimated uncertainty of 0.01 ?rad · mm.
TL;DR: In this article, it was shown that by using a toroidal CCC design, the step-up calibrations become unnecessary, and that high dc current ratios can now be established with this technique with errors smaller than 1 part in 1010.
Abstract: Cryo current comparators (CCC's) are known as current ratio standards with small ratio errors. These small errors are easily proven for windings with 1:1 ratios only. For ratios other than 1:1, say 1: N, the errors must be determined by a step-up calibration procedure based on 1:1 intercomparisons of all windings. This procedure becomes tedious as N gets larger than 1. In addition the uncertainty in the overall error is enhanced by each calibration step. This paper shows that by using a toroidal CCC design the step-up calibrations become unnecessary. Instead of determining the actual error, the special winding configuration has a maximum error which, in principle, can be determined by two simple 1:1 measurements. Therefore, the tedious calibration procedure and the overall uncertainty are reduced. High dc current ratios can now be established with this technique with errors smaller than 1 part in 1010.
TL;DR: Reference averaging as discussed by the authors exploits the asymmetry between the time-variable scene inputs and the nominally constant reference input by averaging many reference measurements to decrease the statistical uncertainty in the reference value.
Abstract: Most radiometers utilize a calibration technique in which measurements of a known reference are subtracted from measurements of an unknown source so that common-mode bias errors are cancelled. When a radiometer is scanned over a varying scene, it produces a sequence of outputs, each being proportional to the difference between the reference and the corresponding input. The reference averaging technique presented herein employs a simple digital algorithm which exploits the asymmetry between the time-variable scene inputs and the nominally constant reference input by averaging many reference measurements to decrease the statistical uncertainty in the reference value. This algorithm is, therefore, optimized by an asymmetric chopping sequence in which the scene is viewed for more than one-half of the duty cycle (unlike the analog Dicke technique) Reference averaging algorithms are well within the capabilities of small microprocessors. Although this paper develops the technique for microwave radiometry, it may be beneficial for any system which measures a large number of unknowns relative to a known reference in the presence of slowly varying common-mode errors.
TL;DR: In this article, the results of computer simulations of clocks, characterized by the power-law model of the spectral density of the normalized frequency fluctuations Sy(f) are described, and the uncertainty of the estimate as predicted by Lesage and Audoin is confirmed.
Abstract: The results of computer simulations of clocks, characterized by the power-law model of the spectral density of the normalized frequency fluctuations Sy(f) are described. The simulation generates slow fluctuations of the normalized frequency y, i.e., white (f0), flicker (f-1) and random walk (f-2) types. The two-smple Allan variance ?2y(?) is used to test the spectral density of the generated time series. The uncertainty of the estimate as predicted by Lesage and Audoin is confirmed. Simulated clock time is obtained by integration of the sequence of normalized frequency samples ?(tk, ?). The simulation of clock ensembles shows that after initial frequency equalization and synchronization, the clock times diverge, but remain normally distributed. The standard deviation of the observed clock time distribution turns out to be very close to t · ?y(? = t), confirming earlier assumptions published by Barnes et al. [2].
TL;DR: A numerical method for investigation of time-division multipliers was described in this paper, which was used for analysis of the Tomota-Sugiyama-Yamaguchi multiplier.
Abstract: A numerical method for investigation of time-division multipliers was described. It was used for analysis of the Tomota-Sugiyama-Yamaguchi multiplier. Comprehensive results in forms of graphs and tables covering all essential characteristics of the multiplier are presented. The calculations were carried out by aid of Control Data computer Cyber 73.
TL;DR: In this paper, two measuring systems driven by microcomputer are presented: flowrate ultrasonic measurements and coherent anti-Stokes Raman spectroscopy, where the integration of standard interfaces and specific electronics made it possible to develop these two applications from a single basic system.
Abstract: Two measuring systems driven by microcomputer are presented: flowrate ultrasonic measurements and coherent anti-Stokes Raman spectroscopy. It is shown how the integration of standard interfaces and specific electronics made it possible to develop these two applications from a single basic system.
TL;DR: In this article, a system which employs open-balanced transmission line structures and UHF CW phase measurement techniques to determine either the thickness or dielectric constant or moisture content of film or slab-like materials in the thickness range of 1 to 400 mil and the relative dielectoric constant range of approximately 2 to 20.
Abstract: A description is given of a system which employs open-balanced transmission line structures and UHF CW phase measurement techniques to determine either the thickness or dielectric constant or moisture content of film or slab-like materials in the thickness range of 1 to 400 mil and the relative dielectric constant range of approximately 2 to 20. Both experimental and analytical results are presented.
TL;DR: In this article, it was shown with supporting experimental results that the error of a voltage transformer supplying a burden can be brought down to the value on open-circuit using an amplifier whose output is approximately equal to the error voltage.
Abstract: It is shown with supporting experimental results that the error of a voltage transformer supplying a burden can be brought down to the value on open-circuit, using an amplifier whose output is approximately equal to the error voltage. The scheme permits the normal requirement that one end of the burden be earthed.
TL;DR: In this article, a measurement system operated by a microprocessor for the dynamic measurement of the complex dielectric constant of sample materials over a wide range of dielectrics constants is described.
Abstract: This paper describes a measurement system operated by a microprocessor for the dynamic measurement of the complex dielectric constant of sample materials over a wide range of dielectric constants. A Q multiplier technique is used for measuring materials which undergo large dynamic increases in dielectric losses. Such increased losses are often encountered when the temperature, pressure, illumination, etc., of a sample dielectric or semiconductor material are altered; or whenever important changes occur in the molecular structure related to changes in the physical state (e.g., liquid-solid) of the test sample. A complete functional diagram of the microprocessor program is presented. For the purpose of these measurements an AIM 65 microprocessor system is expanded to operate with up to 16 I/O ports and 20K bytes of RAM memory.
TL;DR: An ultrasonic sing-around system has been developed that allows the measurement of the velocity of sound in a sample to an accuracy of a few parts in 104 in a period of 10 seconds.
Abstract: An ultrasonic sing-around system has been developed that allows the measurement of the velocity of sound in a sample to an accuracy of a few parts in 104 in a period of 10 ?s A facility is also provided to store a succession of measured sing-around periods This approach enables the continuous measurement of the velocity of sound in materials undergoing rapid changes of thermodynamic parameters such as temperature, magnetic field, or pressure to be achieved As an example, the magnetic-field variations of the velocity of sound in a magnetic gadolinium-yttrium alloy are reported
TL;DR: A microprocessor-based Walsh-Fourier spectral analyzer is described, which includes the sampling of the incoming signal at 64 times the input signal frequency, using a special purpose frequency multiplier module (FMM) and performing a fast Walsh-Hadamard transform of the permuted data sequence.
Abstract: A microprocessor-based Walsh-Fourier spectral analyzer is described. It includes the sampling of the incoming signal at 64 times the input signal frequency, using a special purpose frequency multiplier module (FMM), storing the digital data in a permuted sequence in the system memory under the control of a direct memory access (DMA) controller, and performing a fast Walsh-Hadamard transform (FWHT) of the permuted data sequence. The system uses a single board computer SBC80/10 in an Intel System 80/10 and a special purpose board which includes FMM, DMA, and A/D conversion circuits. Fourier coefficients are obtained via a Walsh to Fourier conversion algorithm; the total process is then faster than the Cooley-Tukey FFT algorithm for a data length of 64 or less.
TL;DR: In this article, the authors proposed a similar but different approach to solve the drift problem in dual-slope integrating analog-to-digital (A/D) converters, which are most frequently used for relatively slow speed conversion.
Abstract: With dual-slope integrating analog-to-digital (A/D) converters, which are most frequently used for relatively slow speed conversion, any drift in the operational amplifiers is a very critical factor in limiting their performance. A method has been proposed to eliminate the drift problem completely [1]. This short paper describes a similar but different approach to solve the problem. Some of the advantages are: no necessity for manual adjustments, the use of inexpensive amplifiers instead of costly units with no performance degradation for the temperature range limited only by digital circuits. The old method is more adaptable to ratiometric conversion, while the new method is more adaptable to normal dual-slope integrating A/D conversion with a reference voltage of opposite polarity to input signals. As is the case with the basic dual-slope converters, no precision components are required.
TL;DR: In this paper, the series impedance of a long solenoid was extended to allow for cylindrical layering of the encircled conductor and it was shown that even an internal layer of reduced conductivity and permeability can be detectable if the frequency is sufficiently low to permit penetration of the primary field.
Abstract: We extend a previous analysis for the series impedance of a long solenoid to allow for the cylindrical layering of the encircled conductor. The results are discussed in the context of nondestructive testing of steel ropes that may have external or internal corrosion. It is shown that even an internal layer of reduced conductivity and permeability will be detectable if the frequency is sufficiently low to permit penetration of the primary field.
TL;DR: In this paper, a digital ventilated psychrometer for direct reading of the relative humidity (RH) from the digital indicator by means of two identical type thermistors is described, based on the temperature to linear voltage converter, the calculator of the dry and wet bulb temperature ratio, converter from the ratio to the voltage proportional to RH, and the analog to digital (A/D) converter.
Abstract: A digital ventilated psychrometer for direct reading of the relative humidity (RH) from the digital indicator by means of two identical type thermistors is described. The method is based on the temperature to linear voltage converter, the calculator of the dry and wet bulb temperature ratio, the converter from the ratio to the voltage proportional to RH, and the analog to digital (A/D) converter. The experimental result by the digital ventilated psychrometer shows that the apparatus makes the direct indication of RH possible. The accuracy of the apparatus is estimated to contain an RH error of less than 2 percent and it is almost the same as that of the Assmann psychrometer. The principal advantage of the apparatus is the direct indication of RH and the capability to use the data directly for the input of the digital data processor.
TL;DR: In this article, a simple technique for precisely controlling the amplitude of oscillators is described, where the control parameter is a voltage and the relationship between this voltage and amplitude is linear.
Abstract: A simple technique for precisely controlling the amplitude of oscillators is described. The control parameter is a voltage and the relationship between this voltage and the amplitude of oscillation is linear. Two applications of the scheme, namely, in amplitude stabilization of oscillators and in generation of stabilized amplitude modulated signals, are discussed. Experimental results agree closely with the expected performances. The scheme is versatile and suitable for mass production.
TL;DR: In this article, an experimental digital data acquisition system for computerized ultrasound imaging studies is developed, where several consecutive ultrasound signals are averaged on a real-time base to enhance the signal-to-noise ratio, to reduce the volume of the data, and to achieve a match of data flow rates between the ultrasound signals and the usual computer input devices.
Abstract: An experimental digital data acquisition system for computerized ultrasound imaging studies is developed. The system requirements for the digital reconstruction of tomographic images from the envelope of ultrasound signals of several megahertz are described. To effectively digitize ultrasound signals, a new digital averager is implemented. Several consecutive ultrasound signals are averaged on a real-time base to enhance the signal-to-noise ratio, to reduce the volume of the data, and to achieve a match of data flow rates between the ultrasound signals and the usual computer input devices. The positions of the ultrasound transducers and the target are controlled by a microprocessor controller. These positions are sensed and also digitized by the averager. The averager transfers the digitized data, both the ultrasound signals and position signals, to a general-purpose computer for further data processing. Experimental data on reconstructing the cross section of a simple target from the ultrasound signals acquired by this system will be presented as an illustration.