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ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / This paper discusses the importance of time measurement and the necessity of time measurement accuracy to data acquisition and analysis. It briefly reviews how time is used in data analysis and how to determine what amount of jitter, latency and phase error is acceptable for various data acquisition systems and analysis methodology. It discusses the relevance of various measurement timing errors and how some of them may be corrected. Finally, this paper discusses various approaches to time tagging of measurements in a distributed network based data system where data is packetized for efficient transmission.

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International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / A radar scatterometer transmits a series of RF pulses and measures the total-power (energy) of the backscattered signal. Measurements of the backscattered energy from the ocean's surface can be used to infer the near-surface wind vector [7]. Accurate backscatter energy measurements are required to insure accurate wind estimates. Unfortunately, the signal measurement is noisy so a separate measurement of the noise-only total-power is subtracted from the signal measurement to estimate the echo signal energy. A common metric for evaluating the accuracy of the scatterometer energy measurement is the normalized signal variance, termed K(p). In designing a scatterometer tradeoffs in design parameters are made to minimize K(p). Spaceborne scatterometers have traditionally been based on fan-beam antennas and CW modulation for which expressions for K(p) exist. Advanced pencil-beam scatterometers, such as SeaWinds currently being developed by NASA use modulated Signals so that new K(p) expressions are required. This paper outlines the derivation of the generalized K(p) expression. While very complicated in its exact form, with a simplified geometry the K(p) expression can be related to the radar ambiguity function. The resulting analysis yields insights into the tradeoffs inherent in a scatterometer design and permits analytic tradeoffs in system performance.

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ABSTRACT Two different implant impression materials viz. a polyether (Impregum ®) and a plaster (Plastogum ®) impression material were used and compared with respect to the accuracy with which abutment positions were reproduced from a stainless steel master model containing five implant analogues. Ten polyether impressions and ten plaster impressions were taken and cast in stone. The positions of the precision impression copings on the twenty impressions were measured using a Reflex Microscope. The positions of the implant analogues on the twenty casts were also measured and compared to the positions on the stainless steel master model. Statistical analysis indicated significant differences between the polyether impression and the plaster impression for full arch implant supported prostheses. The use of plaster resulted in smaller interabutment error but with less predictable variance in dimensions.

Every year, clean, readily available water becomes more and more scarce. Metering water usage is a way to make users more aware of how much water they use, which in turn will increase the desire to conserve water and to reduce their water bill. When meters are tested in their new condition, it is normally performed under ideal laboratory conditions at constant flow rates. Then when the meters are installed in the field, they often are installed in or experience non-recommended conditions that are quite different from the ideal laboratory setting. This study investigated several non-recommended conditions that can exist in a distribution system. The conditions that were simulated were endurance (the study of accuracy as a function of meter throughput), installation (the study of accuracy as a function of upstream piping and meter mounting effects), and flow profile (the study of accuracy as a result of dynamic real world flow variances over time). The meter types that were tested in this study were displacement piston, nutating disc, multi-jet, single-jet, fluidic oscillator, magnetic, and ultrasonic. When comparing the results between the meter types it was found that some meter types were more susceptible than others to the conditions that were simulated. Displacement piston and nutating disc meters had the best overall accuracy performance under the three non-recommended conditions that were simulated.

High-accuracy density measurement data are required to validate equations of state (EOS) for use in custody transfer of natural gas through pipelines. The AGA8-DC92 EOS, which is the current industry standard has already been validated against a databank of natural gas mixtures with compositions containing up to 0.2 mole percent of the heavier C6+ fraction and is expected to predict densities of natural gas mixtures containing higher mole percentages of the C6+ fraction with the same accuracy. With the advances in exploration, drilling and production, natural gas streams containing higher percentages of the C6+ fraction have become available from the deepwater and ultra-deepwater Gulf of Mexico in recent years. High-accuracy, density data for such natural gas mixtures are required to check if the AGA8-DC92 EOS covers the entire range of pressure, temperature and compositions encountered in custody transfer. A state-of-the-art, high pressure, high temperature, compact single-sinker magnetic suspension densitometer has been used to measure densities of two simulated natural gas mixtures named M91C1 and M94C1 after validating its operation by measuring densities of pure argon, nitrogen and methane in the range (270 to 340) K [(26.33 to152.33) oF, (-3.15 to 66.85) oC] and (3.447 to 34.474) MPa [(500 to 5,000) psia]. Measured densities of M91C1, not containing the C6+ fraction show larger than expected relative deviations from the AGA8-DC92 EOS predictions in regions 1 and 2 but agree well with predictions from the recently developed REFPROP EOS, implyingthat the AGA8-DC92 EOS may be unreliable in its present state even for natural gas mixtures not containing the C6+ fraction. Measured densities of M94C1 containing more than 0.2 mole percent of the C6+ fraction deviate from the AGA8-DC92 EOS predictions by more than the expected values in region 1 which is not surprising but the agreement with AGA8-DC92 EOS predictions in region 2 is misleading which becomes evident when the measured densities are compared to the REFPROP EOS predictions. The measured data can be used to recalibrate the parameters of the AGA8-DC92 EOS or to validate an entirely new EOS.

This study investigated how varying the required force level and the direction of force change produced by the thumb and index finger affect the accuracy and variability of a cyclic isometric pinch force-tracking task. Accuracy was examined by both absolute error and relative error for the minimum and maximum force levels and by root mean square error (RMSE) and normalized root mean square error (normalized RMSE) for the force direction reversals. Variability was represented by coefficient of variation of error (CVE). In this study, ‘maximum force’ was defined as the highest force level of a given target force range, and ‘minimum force’ was defined as the minimum force level of the target range. In addition, ‘force increasing to decreasing’ indicated that the track ball motion changed from increasing to decreasing, requiring the performer to exert increasing force up to the maximum force level and then decreasing force to follow the track ball moving toward the minimum force level. The phrase ‘force decreasing to increasing’ indicated the opposite force direction reversal. Eighteen healthy right handed adult volunteers (nine men and nine women; mean age ± SD, 28.3±1.22 and 26.4±1.74) participated in this study. The participants performed a cyclic isometric pinch force tracking task over three different force ranges. Force range 1 was from a minimum force of 3% of maximal voluntary contraction force (MVC) to a maximum force of 6% MVC. In force range 2, the range was from 6% to 12% MVC, and force range 3 was from 12% to 24% MVC. For each force range, five practice trials and ten actual test trials were performed. Rest periods of twenty seconds between trials and one minute between sets of trials (including between practice and actual test trials) were provided to minimize fatigue effects. Absolute error uniformly increased as a function of increasing force. However, the 3% target force level showed larger relative error compared to the 12% target force level (p < 0.05). Another finding of this study was that producing forces positioned at the minimum target level in a range yielded higher absolute error and relative error compared to the same forces when placed at the maximum target level of a different force range. In terms of the reversals, RMSE values were higher at the change from force deceasing to increasing than the opposite, as well as at higher force levels, while normalized RMSE values were greater at lower force levels. CVE was not significantly different between the two reversals in this study. This might indicate that poorer performance during the change from force decreasing to increasing could originate from the effort to maintain consistent performance and additional effort was not beneficial to increase accuracy for the change from force decreasing to increasing. / text