Showing papers in "IEEE Transactions on Instrumentation and Measurement in 1978"
TL;DR: In this paper, a sensor has been developed which uses conductive elastomers to provide a sense of "touch" for computer controlled parts handling equipment, and its dynamic response is characterized.
Abstract: Conductive elastomers are flexible materials whose electrical conductivity varies as a function of the pressure on the material. A sensor has been developed which uses this material to provide a sense of "touch" for computer controlled parts handling equipment. The material has been studied and its dynamic response characterized. Fatigue is identified as a significant obstacle to potential industrial use. The computer interface hardware is described and software which allows the computer to identify types of surfaces is discussed.
96 citations
TL;DR: In this paper, a combined total reflection-transmission method for permittivity measurements at radio and microwave frequencies is described, and analytical expressions for the dielectric constant and the loss factor of a sample, viewed as a two-port in the transmission system, in terms of the measured scattering parameters are given.
Abstract: A combined total reflection-transmission method for permittivity measurements at radio and microwave frequencies is described. Analytical expressions for the dielectric constant and the loss factor of a sample, viewed as a two-port in the transmission system, in terms of the measured scattering parameters are given. ne uncertainty of measurements of the dielectric constant and the loss factor is discussed and a method ofselecting an optimum sample length is suggested.
60 citations
TL;DR: Theoretical expressions for the frequency offset due to spectral impurities in beam-tube frequency standards are given for the case of small sideband to carrier power ratios in this paper.
Abstract: Theoretical expressions for the frequency offset due to spectral impurities in beam-tube frequency standards are given for the case of small sideband to carrier power ratios. They are valid for any value of the separation between the extraneous sideband and the carrier which interrogates the atomic transition, as well as for any value of the power in the carrier. Useful approximations are given in special cases of interest. The effects of the velocity distribution of the detected atoms and of the frequency modulation technique (sine or square wave) are considered.
40 citations
TL;DR: In this paper, the authors considered the general sampling form for the estimate of the Allan variance, and defined a variable proportional to the difference between the average fractional frequency fluctuations over the time interval, to derive the autocorrelation coefficient of the process to which the variable belongs.
Abstract: We considered the general sampling form for the estimate of the Allan variance which is the proposed measure of frequency stability in the time domain, and we defined a variable proportional to the difference between the average fractional frequency fluctuations over the time interval ? to derive the autocorrelation coefficient of the process to which the variable belongs. Calculations of the variance of the estimated Allan variance proved that it may be convergent to its true value with infinite sample number for considered spectral densities of frequency noise. We also applied the results to estimations of frequency measurements to know the influence of the autocorrelation of the process considered. In order to obtain some direct estimates of the confidence of the estimate, distributions of the estimate were plotted by means of computer simulations, and were compared with the chi-square distribution. Those results suggested that for white-and flicker-phase noises (and white-frequency noise) we have to take into account the autocorrelation of the process, while for flicker-or random-walk-frequency noise we may regard the process as a nearly independent (and Gaussian) one.
35 citations
TL;DR: In this article, a phase microstepper is used to steer the real-time USNO to match the final USNO, which is a step towards real time USNO generation.
Abstract: Several changes have recently been made to improve the real time physical approximation of UTC(USNO), the coordinated time scale generated by the U. S. Naval Observatory. A provisional UTC(USNO) is generated in real time, and a physical clock is steered to this time scale by a phase microstepper. When final values for UTC(USNO) are available, a method has been devised to steer the real time UTC(USNO) to match the final UTC(USNO). Further improvement will involve the adoption of an algorithm to generate UTC(USNO) on a real-time basis. Details of this new algorithm are presented.
32 citations
TL;DR: Theoretical analysis of the fringing field effect in the lumped-capacitance method for permittivity measurement for both shunt and series capacitance methods is given in this paper.
Abstract: Theoretical analysis of the fringing field effect in the lumped-capacitance method for permittivity measurement for both shunt- and series-capacitor methods is given. It is shown that while the measured real part of the complex permittivity is larger than the true value by a factor depending on the ratio of the fringing to the parallel-plate capacitances, the imaginary part is not affected by the fringing field.
31 citations
TL;DR: An error analysis is developed in order to define a quality factor, for evaluating the performances of a calibration procedure, by using the invariance property of the cross ratio.
Abstract: Procedures for the calibration of computer-controlled network analyzers in reflection measurements are studied. The major aim of this paper is to develop an error analysis in order to define a quality factor, for evaluating the performances of a calibration procedure. This is done by using the invariance property of the cross ratio, which easily lets one obtain analytical expressions for the residual errors As an application of this technique, a comparison between two actual calibration procedures has been made using an automatic network analyzer. The experimental results favorably compare with the ones obtained on theoretical basis.
31 citations
TL;DR: In this article, a method for the determination of ac-dc transfer error as a function of current in thermoelements is presented, and the transfer error variation has been determined for two 10 mA thermistors at an ac excitation frequency of 57 Hz.
Abstract: A method is presented for the determination of ac-dc transfer error as a function of current in thermoelements. To test the method the transfer error variation has been determined for two 10 mA thermoelements at an ac excitation frequency of 57 Hz, and the results compared. On the basis of one of these determinations a dual multijunction thermal converter has been calibrated to provide a check. A number of single junction thermoelements have also been calibrated, and results indicate significantly larger errors as I ? 0 than expected on theoretical grounds. Also, for all thermoelements with Evanohm heaters, the error variation follows a square law of opposite sign to that predicted by theory. An explanation is offered for this behavior. Results indicate that changes in transfer error with current level can be determined to ~1 ppm. Absolute transfer errors for the thermoelements tested however, are probably not known to better than a few ppm.
30 citations
TL;DR: In this paper, a system for measuring the complex permittivities of rigid dielectric sheet materials at millimeter wavelengths, using free-space transmission techniques and Brewster angle determinations, is described.
Abstract: A system is described for measuring the complex permittivities of rigid dielectric sheet materials at millimeter wavelengths, using free-space transmission techniques and Brewster angle determinations A first-order analysis is given for the effect of multiple reflections in thick low-loss dielectric sheets, under conditions of oblique incidence Values of ?r and tan ? are given for selected sheet materials at 35 GHz and 25°C, that are estimated to be accurate to ±5 percent
30 citations
TL;DR: A high-precision standard for the calibration of audio-frequency phase meters has been designed using a microprocessor to generate the test signals.
Abstract: A high-precision standard for the calibration of audio-frequency phase meters has been designed using a microprocessor to generate the test signals. The accuracy is better than 0.01 degree over a frequency band from dc to 5 kHz and decreases to 0.1 degree at higher audio frequencies.
27 citations
TL;DR: In this paper, a simple double current source, designed for supplying two windings of a cryogenic current comparator (CCC), is described, where the ratio of the two currents is preadjusted by means of an auxiliary resistor ratio and precisely regulated by a CCC associated with a SQUID detector.
Abstract: A simple double current source, designed for supplying two windings of a cryogenic current comparator (CCC) is described. The ratio of the two currents is preadjusted by means of an auxiliary resistor ratio and precisely regulated by a CCC associated with a SQUID detector. This enables accurate ratio calibration of four-terminal standard resistors at room temperature, taking advantage of high accuracy (better than 1 × 10-9) and resolution (5 × 10-9 A in a one-turn winding) of the CCC. Operational experience in the calibration of standard resistors (1:10 ratio) is reported. In addition, the use of this double source is suggested for the realization of a cryogenic voltage standard.
TL;DR: In this article, an automated calorimetric measurement system using a microcomputer has been developed for determining the effective efficiency of a bolometer mount in the millimeter-wave region.
Abstract: An automated calorimetric measurement system using a microcomputer has been developed for determining the effective efficiency of a bolometer mount in the millimeter-wave region This system consists of a calorimetric measurement part, a bolometric measurement part, and a control/data processing part The system has been constructed and experimented in 35-GHz band The accuracy of the system has been estimated within ±037 percent
TL;DR: In this article, a binary resistive divider network was found which utilizes N cascaded DPDT reversing switches plus one SPDT switch for an N-bit divider.
Abstract: A binary resistive divider network has been found which utilizes N cascaded DPDT reversing switches plus one SPDT switch for an N-bit divider. The network features a simple and accurate method for internal calibration. With a fixed divider input voltage the power dissipated in each resistive element is independent of switch setting.
TL;DR: In this article, an electronic method is described, in several variations, that is rapid, simple, and well adapted to microprocessor control, making use of the fact that the desired mode of vibration is shifted in frequency by a variable series capacitor.
Abstract: The frequency- or immittance-temperature anomalies occurring in quartz-crystal resonators are generically called activity dips. Because of their potentially disastrous effects on oscillator and filter performance, testing for their presence can represent a considerable addition to the manufacturing cost. An electronic method is described, in several variations, that is rapid, simple, and well adapted to microprocessor control. The electronic method obviates tedious and costly temperature runs. It makes use of the fact that the desired mode of vibration is shifted in frequency by a variable series capacitor, while interfering modes, that cause activity dips, are nearly unaffected.
TL;DR: An absolute measurement of loss angle has recently been completed at NBS as mentioned in this paper, which utilized a special toroidal cross capacitor in which the effects of dielectric films are greatly attenuated.
Abstract: An absolute measurement of loss angle has recently been completed at NBS. The measurement utilized a special toroidal cross capacitor in which the effects of dielectric films are greatly attenuated. The resulting unit of loss angle has an estimated uncertainty of 0.02 ?rad at an optimum frequency of 1592 Hz.
TL;DR: In this article, a new method for the dynamic measurement of the passive parameters of a microwave cavity is described, where both the resonant frequency (f0s) and the loaded Q factor (QLs) are measured simultaneously from active frequency signals generated by a closedloop circuit containing the test cavity.
Abstract: A new method for the dynamic measurement of the passive parameters of a microwave cavity is described. Both the resonant frequency (f0s) and the loaded Q factor (QLs,) are measured simultaneously from active frequency signals generated by a closedloop circuit containing the test cavity. Resonant frequency deviations of up to 20 MHz are measured with an accuracy of better than ±0.25 percent, and loaded Q-factor variations (from 500 to 7000) are measured with an accuracy of better than ±1.2 percent. The unperturbed cavity resonance was at 2452.0249 MHz, and the time of measurement of each cavity parameter was < 1 s.
TL;DR: In this paper, theoretical and experimental studies on Cs beam optics using quadrupole and hexapole magnets and a combination of both, are reported, and the efficiency of the deflection system and the velocity distribution in the beam have been computed for extended beam sources and compared with experimental results.
Abstract: Results on theoretical and experimental studies on Cs beam optics using quadrupole and hexapole magnets and a combination of both, are reported. The efficiency of the deflection system and the velocity distribution in the beam have been computed for extended beam sources and compared with experimental results. An appropriate combination of magnets yielded a strong beam with a narrow relative half-width velocity range of about 7 percent. Design problems of Cs standards are discussed. A new wedge-shaped analyzer flop-in magnet is under study. Frequency shifting effects due to Majorana transitions are reported and the frequency shifting mechanism is discussed.
TL;DR: In this article, an automated measurement system for a micromachine, which is a laboratory model of a large turbogenerator, used for practical evaluation of proposed new control schemes involving on-line computer control.
Abstract: This paper describes an automated measurement system for a micromachine, which is a laboratory model of a large turbogenerator, used for practical evaluation of proposed new control schemes involving on-line computer control. Rotor angle, slip, and various electrical quantities have to be measured rapidly and accurately, with immediate graphical display of outputs, and frequent updating for control purposes. The philosophy adopted is to present data to the computer in its most basic form, to be processed by efficient software routines.
TL;DR: In this paper, the authors demonstrate how structure functions can be used to identify power-law type spectral density components 1/fv associated with oscillator phase noise measurements when polynomial type systematic drifts are present.
Abstract: In this paper we demonstrate how structure functions can be used to identify power-law type spectral density components 1/fv associated with oscillator phase noise measurements when polynomial type systematic drifts are present. The technique discussed is new and novel in that it avoids the usual errors that are introduced in the measurement due to removing systematic trends in the observed data by the usual estimation detrending techniques. Several applications of the theory are given and a convenient and expedient look-up table is provided for those who perform measurements. The paper begins by summarizing accepted frequency stability measures and places these into perspective with structure functions of oscillator instability. The paper ends by showing how the rms fractional frequency deviation differs from the Allan variance; numerical examples are given.
TL;DR: In this article, the authors derived the impedance per unit length of a long solenoid of many turns that contains a cylindrical sample with a specified conductivity and magnetic permeability, provided all transverse dimensions are small compared with the free space wavelength.
Abstract: Using an idealized model, we deduce the impedance per unit length of long solenoid of many turns that contains a cylindrical sample. The sample with a specified conductivity and magnetic permeability need not be centrally located within the solenoid provided all transverse dimensions are small compared with the free-space wavelength. The derivation is relatively straightforward and it provides a justification for earlier use of the impedance formula. The dual problem , where the solenoid is replaced by a toroidal coil is also considered. It is shown that both excitation methods have merit in nondestructive testing procedures.
TL;DR: In this article, an intercomparison of the ratio errors of the national power frequency current ratio standards of the National Research Council of Canada and the Physikalisch-Technische Bundesanstalt of Germany has been carried out by means of transfer standard current transformers at ratios of 60 000 A : 5 A.
Abstract: An intercomparison of the ratio errors of the national power frequency current-ratio standards of the National Research Council of Canada and the Physikalisch-Technische Bundesanstalt of Germany has been carried out by means of transfer standard current transformers at ratios of 60 000 A : 5 A, 50 000 A : 5 A, 40 000 A : 5 A. Typical agreement between calibrations at both laboratories is of the order of 0.5 to 1.5 ppm. Details of the transfer standards are given.
TL;DR: In this article, a new approach to the speed measurement of small dc shunt/permanent magnet motors is presented, based on the measurement of the back EMF of the motor, with the addition of a sensing resistor in series with the armature and associated simple electronic circuitry.
Abstract: A new approach to the speed measurement of small dc shunt/permanent magnet motors is presented. It is based on the measurement of the back EMF of the motor, with the addition of a sensing resistor in series with the armature and associated simple electronic circuitry. This can replace the conventional speed measuring transducers like tacho-generator and magnetic-optical pickups, offering a low weight, compact and reliable system and eliminating the mechanical coupling between the motor and the transducers. The experimental results and the steady-state response of the control scheme are also presented.
TL;DR: In this paper, the frequency of commercial Ar+ lasers at 582 THz was stabilized by an external device mainly consisting of a 127I2 cell, two photodetectors, an electronic divider, and a conventional servo loop, using the 3f locking technique.
Abstract: The frequency of commercial Ar+ lasers at 582 THz was stabilized by an external device mainly consisting of a 127I2 cell, two photodetectors, an electronic divider, and a conventional servo loop, using the 3f locking technique. The symmetry of the 3f signals was tested by two methods. In the neighborhood of the central zero crossing at separations of up to ±300 kHz no asymmetry could be detected within 4 × 10-13 v. The stabilized frequency?being independent of the modulation width?is reproducible to better than ±2 × 10-11 v. From the small dependence of the frequency on the I2 vapor pressure of -5 kHz/Pa an uncertainty of less than ±4 × 10-11 v is assumed. Thus the selected 127I2 lines at v = 582 THz/? = 515 nm should be promising candidates as optical frequency or wavelength standards.
TL;DR: In this article, two circuits are described which frequency lock a spectrally pure quartz crystal oscillator to an independent quartz crystal resonator, and the performance of the composite system is predicted based on the measured performance of its components.
Abstract: The intrinsic noise of the best quartz crystal resonators is significantly less than the noise observed in oscillators employing these resonators Several problem areas common to traditional designs are pointed out and a new approach is suggested for their solution. Two circuits are described which frequency lock a spectrally pure quartz crystal oscillator to an independent quartz crystal resonator. The performance of the composite system is predicted based on the measured performance of its components.
TL;DR: In this paper, a portable rms digital voltmeter (DVM) was developed at NBS to support vibration measurements over the ranges of 0.1 to 50 Hz and 2 mV to 10V.
Abstract: A portable rms digital voltmeter (DVM) has been developed at NBS to support vibration measurements over the ranges of 0.1 to 50 Hz and 2 mV to 10V. A self-contained calibrator provides for self-calibration and may be used for calibrating other VLF voltmeters. The calibrator basically consists of a Kelvin-Varley divider fed by a reference voltage (either dc or sinewave generated by a ROM-DAC combination) A multijunction thermal converter (MJTC) was selected as the sensing device in the rms/dc converter of the DVM since its low ac/dc difference facilitates calibration of the ac calibrator. Factors affecting accuracy and response time are analyzed. The DVM response time is 40 s for the lowest input frequency. Its accuracy (percent of reading) is 0.1 percent above 0.5 Hz and 5 mV and 0.2 percent below these values. The ac calibrator accuracy is 0.02 percent. Measurement accuracy improves by a factor of about 4 for transfer measurements (comparing input voltages with ac calibrator voltages) Means for extending this accuracy to 0.01 percent are discussed.
TL;DR: In this paper, the two resistors which form the ratio are constructed as two separate networks of nominally equal resistors and each network is chosen such that there is a dual network which can be constructed from the same set of resistors.
Abstract: The two resistors which form the ratio are constructed as two separate networks of nominally equal resistors. Each network is chosen such that there is a dual network which can be constructed from the same set of resistors. Two configurations with the same nominal ratio are obtained by switching each network to its dual and interchanging their positions in the ratio. The mean ratio is a very close approximation to the nominal value. As an example, it is shown that only six resistors are required to produce all steps of a single-decade voltage divider with a mean accuracy of 1 in 106 using resistors adjusted to 1 in 103.
TL;DR: In this paper, the authors developed and improved the phase meter using relative counting A/D conversion system, by measuring the duty factor of repetition pulse with arbitrary frequency, and obtained the digital phase meter with errors at most within 0.01 percent and 0.001 percent up to 10 Hz-100 kHz.
Abstract: As an example of digital measuring system for improving the measuring processes, etc., the authors have developed and improved the phase meter using relative counting A/D conversion system, by measuring the duty factor of repetition pulse with arbitrary frequency. The digital phase meter with errors at most within 0.01 percent and 0.001 percent up to 10 Hz-100 kHz, about 0.1° at 1 MHz has been obtained by applying the theoretical and experimental investigations on it.
TL;DR: In this paper, a long-term frequency shift with respect to TAI was observed in two hydrogen masers by direct frequency comparisons between them and primary cesium standards, attributed to an increase in the wall shift of the storage bulb in the maser.
Abstract: A long-term frequency shift, with respect to TAI, has been observed in each of two hydrogen masers by direct frequency comparisons between them and primary cesium standards. The shift is attributed to an increase in the wall shift of the storage bulb in the maser. Depending on the storage bulb used, this increase was found to be between 3 × 10-13 and 8 × 10-13 per year. Possible reasons for the observed shift are discussed.
TL;DR: A new technique of measuring low frequencies accurately has been described and the whole scheme can be implemented using TTL integrated circuits.
Abstract: A new technique of measuring low frequencies accurately has been described. The whole scheme can be implemented using TTL integrated circuits.
TL;DR: In this article, a method of measuring the permittivity of dielectric materials using a resonator terminated by an infinite sample is described, based on measurements of the changes of the resonant frequency and the Q factor produced by the test sample.
Abstract: A method of measuring the permittivity of dielectric materials using a resonator terminated by an infinite sample is described. The method is based on measurements of the changes of the resonant frequency and the Q factor produced by the test sample. The method is particularly suitable for lossy materials with a high dielectric constant, namely, biological substances and tissues. Analytical and graphical solutions, which lead to material permittivity from experimental data, and a discussion of the measurement uncertainty are presented. The experimental results obtained for water are given.