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Instrumentation and Measurement Technology Conference, 1989. IMTC-89. Conference Record., 6th IEEE

Date 25-27 April 1989

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Displaying Results 1 - 25 of 114
  • Conference Record. IEEE Instrumentation and Measurement Technology Conference (Cat. No.89CH2707-8)

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    Freely Available from IEEE
  • A 1 Ms/s 16-bit analog-to-digital converter

    Page(s): 6 - 9
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    The author describes a 1-megasamples/s 16-bit analog-to-digital converter (ADC) that uses a subranging conversion technique. High accuracy at a 1-MHz conversion rate is obtained with novel circuits developed for a track-and-hold device, a residue amplifier, and a digital-to-analog converter. Design aspects of these key functional circuits are presented. A prototype ADC was fabricated on a printed-circuit board and tested. Curve-fit test results show that up to 100 kHz, the effective bits decrease to 14 bits due to wideband noise. However, signal bandwidth is commonly restricted in spectrum analysis, so a dynamic range of over 96 dB can be obtained View full abstract»

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  • Experimental studies of the RF-DC differences of voltage standards

    Page(s): 171 - 174
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    The RF-DC differences (d) of primary voltage standards were determined by experimental and theoretical procedures. The voltage standards, with different operating principles and designs, have been compared with CTVCs (coaxial thermal voltage converters) at frequencies from 1 to 100 MHz. The method recommended for determining the d values is to derive an empirical formula and then to correct if from measured data. The uncertainty of primary voltage standards established by this method is ±0.007% at 1 MHz, ±0.01% at 3 MHz, ±0.02% at 10 MHz, 0.07% at 30 MHz, ±0.15% at 50 MHz, and ±0.2% at 100 MHz. This specification is shown to be reliable while leaving sufficient margin for error View full abstract»

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  • Interpolation techniques for real-time multifrequency waveform analysis

    Page(s): 325 - 331
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    It is well-known that in discrete-Fourier-transform- (DFT-) based waveform analysis of multifrequency signals, spectral parameter accuracy can be increased by windowing the time samples and interpolating the DFT coefficients. It is shown that some relationships used in interpolation are affected very little by the number of processed samples, so that only the characteristics of the analyzed signal and the required accuracy affect the choice of this parameter. In particular, this makes the approach well suited for real-time analysis of signals with slowly time-varying spectra. Polynomial approximations of some relationships reduce the processing effort and, allow a greater freedom in the choice of the window functions, improving both accuracy and frequency resolution View full abstract»

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  • Wideband microwave pulsed reflectometer using a six-port junction

    Page(s): 529 - 532
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    A six-port reflectometer technique is extended to make pulsed-RF measurements. It is shown that a time resolution of the order of 1 μs is possible in both repetitive and single-shot mode of operation. A proof of principle of the method is obtained using passive and active loads. A simple method for the linearization of diode detector response is also presented. Because of its good time resolution, the proposed technique can be used to study thermal effects in high-power solid-state amplifiers or to characterize pulse devices used in phased-array radars View full abstract»

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  • High-pressure polarimetric sensor using birefringent optical fibres

    Page(s): 414 - 417
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    A novel fiber-optic high-pressure sensor has been developed for a pressure range up to 200 MPa and for a standard range of temperatures. The sensor is based on the effect of polarization coupling between two orthogonally polarized eigenmodes of the highly birefringent, polarization-preserving optical fiber used as a sensing element. When linearly polarized light, is launched into the fiber at an angle of 45° to each of its principal polarization axis, the output signal (monitored in the direction perpendicular to the direction of the major axis of the polarization state of the light exiting from the fiber) is directly dependent on external high pressure. The sensing element was configured inside a high-pressure chamber using a specially designed, fiber-optic lead-through system. Preliminary tests of the sensor show that its sensitivity is far superior to that of currently used solid-state sensors of high pressure. The author discusses principles, construction, and operation of the sensor and its performance under various conditions, including different pressure and temperature coefficients of the output signal View full abstract»

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  • An easy-to-use, host-independent data acquisition system

    Page(s): 86 - 91
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    The design of a host-independent data-acquisition system is described. Host independence is achieved by using an RS-232 communication link between the host and data-acquisition system. The capability for system expansion, both in size and functionality, is achieved through the use of a system bus and an accompanying 8-bit microprocessor for communication and control. The motivation for the system's development was to reduce the cumbersome interface problems frequently encountered when an acquisition system is moved from one host computer to another View full abstract»

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  • The electronic crusher gauge

    Page(s): 563 - 566
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    A pressure-measuring device called the electronic crusher gauge is described. The volume of the gauge is small enough (38 cm3) that it can be placed in the powder chamber of large- or medium-caliber guns, with chamber volume not less than 4 dm3. The gauge is characterized by digital data recorded with a sampling frequency from 0.1 to 100 kHz and directly transmitted under PC control. The measuring principles and construction features of this gauge are detailed, a bore pressure curve for a certain type of gun is given, and the results are compared with those measured by a conventional copper crusher gauge View full abstract»

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  • High accuracy location of faults on electrical lines using digital processing of sampled data records from a reflectogram

    Page(s): 462 - 466
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    A signal processing algorithm is developed to estimate the location of a discontinuity, e.g. a fault, on an electrical line. It is applied to fast sampled data and performs pecstral analysis of pulsed signals. The pecstrum algorithm is based on a transform similar to the one used in the cepstrum technique. It is demonstrated both theoretically and experimentally that the performance of the pecstrum estimator is significantly better than that of previously proposed methods. The proposed solution is operational in industrial digital reflectometers and has proved to be robust and successful in practice. With respect to cable-fault location, accuracies up to 30 cm are obtained when a fast, 20-MHz, 8-bit sampler is used for the acquisition of pulsed signals in a reflectogram View full abstract»

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  • A system for surveying power quality

    Page(s): 400 - 401
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    The author describes a system that is designed to survey power disturbances at representative sites across the continental USA. Disturbance data gathered from remote power monitors are transmitted over telephone lines to a central personal computer to be processed and saved in a database for further analysis and study. A summary of the system architecture is given, and special features of programs and data are discussed View full abstract»

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  • Efficient instrument design using IEEE 488.2

    Page(s): 66 - 70
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    IEEE 488.2 defines standard formats, protocols, and common commands for IEEE 488 programmable instrumentation. Conventional software techniques can be used to write a parser that implements the formats and common commands. Such a parser requires a simple data stream interface, where data are simply gotten (commands) or placed (responses). The author describes a software driver for an IEEE 488 interface. This driver provides a simple data stream interface to the parser while conforming to the protocol requirements of IEEE 488.2. The crux of this implementation is the isolation of the message exchange control protocol, which is implemented with a simple state machine, from the parser. The protocol requirements of IEEE 488.2 have been converted to a state machine where each transition is the result of an external signal. In this process some anomalies in IEEE 488.2 have been identified and corrected View full abstract»

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  • New in-situ calibration of diode detectors used in six-port network analyzers

    Page(s): 533 - 535
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    The authors present a novel method of calibrating the diode detectors used in six-port network analyzers, without disconnecting the diodes. The method uses only a precision variable attenuator or a power meter with no additional directional coupler. The important feature of this method is that no actual measurement of power is required to calibrate the diode detectors for six-port operation. It is very well suited to in-situ calibration of the diode detection circuits for operation of the six-port with pulse signals when the average power detected by the power meter drops to very low levels for low duty cycles. In these cases, the precision variable attenuator method is required. Measurement results are presented View full abstract»

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

    Page(s): 223 - 227
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    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 View full abstract»

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  • A new measurement for television transmission characteristics

    Page(s): 508 - 512
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    The author describes an open-loop measurement system for determining TV transmission characteristics. Measurements of transmission from the studio to the final relay station can be performed. A teletext (digital-code-service) signal is inserted into a video signal on the same line. Two carriers are used: the measured signal is transmitted on the video carrier, and the audio carrier is used for sending the reference signal. The signal generator for the video transmitting section has a 1/2 divider adjustable to any type of line, such as a narrow audio frequency line. The receiver of the RF measured signal has a second multiplier to regenerate the reference signal. A phase comparator measures the transmitting line characteristics by comparing the measured signal with the reference signal. The reference signal accuracy of the method has been analyzed to certify the validity of the test results. When a 10-kHz subreference signal modulated at a modulation index of 30% is transmitted from a TV transmitting station to a receiving site, the calculated phase rotation angle is 0.75 rad View full abstract»

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  • New internationally adopted reference standards of voltage and resistance based on the Josephson and quantum Hall effects

    Page(s): 175 - 177
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    By international agreement, starting on January 1, 1990, new reference standards of voltage and resistance based on the Josephson and quantum Hall effects, respectively, are to come into effect worldwide. Implementation of the new standards in the US requires that the value of the present national representation of the volt and ohm maintained at the National Institute of Standards and Technology (NIST) be increased by 9.264 and 1.69 parts per million (ppm), respectively. These changes are sufficiently large that literally thousands of electrical standards, measuring instruments, and electronic systems throughout the US will have to be adjusted in order to conform with the new US volt and ohm representation View full abstract»

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  • Automatic generation of NC-code for hole cutting with in-process metrology

    Page(s): 45 - 52
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    A novel method for milling flat-bottomed circular holes with more accurate diameters has been added to the data preparation software for the vertical workstation of an automated manufacturing research facility. Additional design functions, a new process planning function, and a new numerical control (NC) code-generating function have been added to the software to implement the method. The cutting algorithm uses a touch probe to measure the diameter of the semifinished hole during the cutting process. The radius used to finish cut the hole is then changed from its nominal value by an amount equal to the difference between the nominal and measured values of the radius of the semifinished hole. The new hole milling process corrects errors caused either by tool deflection or by using a tool whose actual radius differs from its nominal radius. With this process, errors in the diameter of a hole cut with an end mill have been reduced from roughly five mils (plus tool diameter error) to about one mil (regardless of tool diameter error), as compared with a process that does not measure during cutting View full abstract»

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  • A microprocessor-based three phase power transducer

    Page(s): 98 - 102
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    The authors present the design and implementation of a three-phase power transducer based on microprocessor technology. The transducer is intended for applications in which fast response time and flexible operation are important. This transducer can produce its outputs after each cycle (16.6 ms for 60-Hz transmission systems). The transducer is considered flexible because it is capable of supplying other output beyond simple three-phase power, voltage, and current. The theory of operation of the transducer, its present limitations, and proposals for future performance enhancements are presented View full abstract»

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  • High-precision, rapid readout of cryogenic temperature sensors in the Space Shuttle environment

    Page(s): 14 - 18
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    A compact and rugged system for performing 4-wire determination of the resistance of germanium resistance thermometers near 1 to 1 part in 65000 in 1 s using 20-nW excitation is described. Constraints unique to cryogenic and aerospace, systems are addressed. A microcomputer-controlled, hybrid analog/digital design is presented. Test results are presented, and future developments are discussed View full abstract»

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  • State estimation for random error reduction in avionic measurement applications

    Page(s): 388 - 393
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    A state estimation algorithm for flight measurement systems is studied for RPV (remotely piloted vehicle) telemetry and control applications. This system transmits real-time measurement data from the airborne system to the ground system. The effectiveness of four adaptive filter techniques used together with bad data elimination in reducing error is investigated theoretically and by simulation. The performance for white error and colored error is tested by simulating of a barometric/inertial system. The adaptation of appropriate filter algorithms for aircraft applications is highlighted View full abstract»

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  • Data handling capacity of a real transmission line. I. Noiseless case

    Page(s): 471 - 484
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    A computation technique is described for determining the maximum error-free data rate for a transmission line whose attenuation and phase shift are known at discrete frequencies. Results are obtained from manufacturer's data for commercially available twisted pair lines of gauges AWG 19, 22, 24, and 26, for lengths up to about five kilometers. The capacity of each line appears to fall off somewhat more strongly with line length than the inverse length dependence that is conventionally accepted, but not as strongly as the inverse square rate assumed in some work View full abstract»

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  • 800 Ms/s arbitrary function generator

    Page(s): 238 - 242
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    An arbitrary function generator capable of running from very low clock rates up to 800 Ms/s has been developed with sufficient timing and noise margins to allow repeatable unit-to-unit production and long operational life. The generator uses an 8-bit gallium arsenide digital/analog converter and a multiplexing scheme to allow waveform memory to be stored in a relatively low-speed memory. Critical timing details that allow operation at such a high speed are presented. Methods for loading signals and noise into the memory are also touched upon View full abstract»

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  • Software technology for automated measurements

    Page(s): 259 - 262
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    The author describes three different personal-computer-based approaches to the software support of measurement applications. The first approach is for skilled programmers who want very flexible tools in a wide variety of programming languages. The second adds programming productivity tools to eliminate much of the detailed programming. The third and most advanced software system attempts to eliminate instrumentation programming entirely with a highly graphical environment View full abstract»

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  • Performance comments on manganin resistance gauges under high static pressures

    Page(s): 559 - 562
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    The performance of manganin resistance gauges under high static pressure is evaluated. The accuracy of several interpolation- (or extrapolation-) based mathematical-models is compared. It is shown that if the gauges used at pressures below 1 GPa are calibrated at a given constant temperature and used at that temperature, the complete mathematical-model is unnecessary. However, a complete model for the variation of resistance with both pressure and temperature is required in the pressure range from 1 GPa up to 20 GPa, because the temperature changes due to compression or expansion of the pressure-transmitting medium can be quite pronounced View full abstract»

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  • RMS and average errors resulting from low pass filter characteristics in instrumentation systems

    Page(s): 72 - 75
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    Rectangular, steplike waveforms, occurring in many physical systems, are passed through sensors or signal conditioners having, in many cases, low-pass filter characteristics. The filtered waveforms are sampled by A/D (analog/digital) converters and the average or RMS (root-mean-square) values calculated. The author describes the effects of the low-pass filter characteristics on the average and RMS values of the waveforms and the analysis method used to determine the effects. It is shown that once the data-acquisition-system component under consideration has been modeled by an s-domain transfer function and the input waveform is known, the solution process is mechanical. By the way of example, the method is applied to a measurement problem and the results provided. The effects of assuming unit step excitation rather than physically realizable exponential step inputs are also discussed View full abstract»

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  • Superfluid helium tanker instrumentation

    Page(s): 372 - 376
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    An instrumentation system for a 1992 Space Shuttle flight demonstration of superfluid-helium tanker and transfer technology is presented. The system measures helium temperatures, pressures, flow rates and mass and the amount of liquid or vapor present. It consists of analog and digital portions which provide a fault-tolerant, compact, relatively lightweight, space-qualified electronics system. The data-processing hardware and software are ground-commandable, perform measurements asynchronously, and format telemetry for transmission to the ground. A novel heat-pulse mass gaging technique is described, and a new liquid/vapor sensor is presented. Flowmeters for superfluid helium are discussed, and the superfluid helium fountain effect pump is described. Results of tests to date are presented View full abstract»

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