Instrument errors

For the practical implementation of the above mentioned facts, the portable electronic digital coercive force meter with self-contained power supply, attached converter and closed type magnetic core. Instrument error is 5 %. ... 

During testing a depth resolution of 50-80 micron and a lateral resolution of 20-40 micron was achieved. The spatial resolution was limited not mainly hy source or camera properties, but by the accuracy of compensation of the instrumental errors in the object movements and misalignments. According to this results a mote precision object rotation system and mote stable specimen holding can do further improvements in the space resolution of microlaminography. 

Effect of Indeterminate Instrumental Errors on Relative Uncertainty in Concentration... 

Relative uncertainties for absorption spectrophotometry as a function of absorbance for the three categories of indeterminate instrumental errors (see Table 10.8 for equations). 

Every instrument is likely to have a slight error, and the magnitude of this error, if it exists, must be known. It is meaningless, for example, to record an instrument reading as 51.3 ppm when in fact there is a known instrument error of 5%. It is also meaningless to report the average of several readings by a number which cannot be read on the instrument itself. 

In most situations analysts can achieve a rapid reasonable separation of compounds using an appropriate standard CE method with generic operating conditions [877]. This eliminates or reduces dramatically the need for method development. Major instrumental error sources in CE are detection, integration and injection. General guidelines for validation of CE methods are available and similar to those of HPLC [878]. Validated CE methods often perform the same as, or better than, the corresponding HPLC methods. 

The objective of this test was to present and analyze suitable experimental results for verif ying quantitatively the use of the above-mentioned three corrections with the W-3 correlation for predicting the DNB heat flux in a rod bundle. Uncertainties in the data due to instrument errors and heater rod fabrication tolerances... 

Table 5.11 Data uncertainties due to instrument errors and fabrication tolerances... 

Constant instrumental error 1%. Curve A photovoltaic detector. Curve B photomultiplier detector. 

Determinate errors may be constant or proportional. The former have a fixed value and the latter increase with the magnitude of the measurement. Thus their overall effects on the results will differ. These effects are summarized in Figure 2.1. The errors usually originate from one of three major sources operator error instrument error method error. They may be detected by blank determinations, the analysis of standard samples, and independent analyses by alternative and dissimilar methods. Proportional variation in error will be revealed by the analysis of samples of varying sizes. Proper training should ensure that operator errors are eliminated. However, it may not always be possible to eliminate instrument and method errors entirely and in these circumstances the error must be assessed and a correction applied. 

The previous method supposes complete knowledge of the system and depends on the measurement quality of instruments (errors, availability), leading to severe effects on the accuracy of the on-line estimates. Therefore, a good noise filtration algorithm (like the Kalman filter or derivative) should be employed to improve the reliability of the estimated values before their use. 

The copyrolysis of 1 wt% dibromotetrafluoro-p-xylylene with commercially available hexafluoro-p-xylene (Aldrich) with metals was examined and it was found that it was indeed possible to prepare films that were spectroscopically indistinguishable from those deposited from dimer. The PA-F films obtained are of excellent quality, having dielectric constants of2.2-2.3 at 1 MHz and dissociation temperatures up to 530°C in N2. A uniformity of better than 10% can be routinely achieved with a 0.5-gm-thick film on a 5-in. silicon wafer with no measurable impurities as determined by XPS. During a typical deposition, the precursor was maintained at 50°C, the reaction zone (a ceramic tube packed with Cu or Ni) was kept at 375-550°C, and the substrate was cooled to -10 to -20°C. The deposited film had an atomic composition, C F 0 = 66 33 1 3 as determined by XPS. Except for 0, no impurities were detected. Within instrumental error, the film is stoichiometric. Poly(tetrafluoro-p-xylylene) has a theoretical composition ofC F = 2 1. Figure 18.2 illustrates the XPS ofthe binding energy... 

Ti measurements were performed at 250, 275 and 300 K by inversion-recovery (7r-T-7r/2-5T i) sequences on a JE0L-FX-100 and a Bruker WP-80 spectrometers. On this latter the "repetitive frequency shift" method of Brevard et al. (18) was used, where two systematic instrumental errors (drift, round off errors in FT processing.. .) are uniformly distributed through all data points. The NOE measurements are reproducible within 10-20 %, while the average standard error on the Tj values is of about 5 %. 

The critical part of such an optimization scheme is the analysis and reconciliation of the measurements, to ensure accurate and consistent data and the detection of instrument errors and faults. The overall scheme for the on-line monitoring and optimization of the column is also shown in Fig. 10. Data from the plant are first... 

In nominally identical experiments the differences between rates, maximum optical densities and conductivities were never greater than could be accounted for by instrument errors or by errors arising from computation of concentrations. No inexplicable irreproducibilities were found. 

Finally, when determining the sense of nonequivalence of either very closely spaced diastereotopic resonances or resonances superimposed on other solute signals, it is wise to examine solute behavior using first one, then the other CSA enantiomer under the same conditions. This minimizes the possibility of instrumental error, from impurities, or from otherwise unanticipated sources. Incremental addition of racemate is another good check on the reality of a tenuous observation. 

The relationship takes into account that the day-to-day samples determined are subject to error from several sources random error, instrument error, observer error, preparation error, etc. This view is the basis of the process of fitting data to a model, which results in confidence intervals based on the intrinsic lack of fit and the random variation in the data. 

As in many such problems, some form of pretreatment of the data is warranted. In all applications discussed here, the analytical data either have been untreated or have been normalized to relative concentration of each peak in the sample. Quality Assurance. Principal components analysis can be used to detect large sample differences that may be due to instrument error, noise, etc. This is illustrated by using samples 17-20 in Appendix I (Figure 6). These samples are replicate assays of a 1 1 1 1 mixture of the standard Aroclors. Fitting these data for the four samples to a 2-component model and plotting the two first principal components (Theta 1 and Theta 2 [scores] in... 

Most samples may be prepared by dissolution in water. The final concentration should be optimized according to the aim of the analysis, counterion or impurity analysis. For the control of impurities, the main counterion may be fairly overloaded. This may have an impact on the ionic strength of the sample and will produce a disturbed peak profile for the main compound. When solubility problems are encountered, up to 30% of methanol, ethanol, or acetonitrile may be added to improve solubility. However, the presence of too much organic solvent may produce an instrumental error, because the conductivity of the sample plug will differ too much from BGE conductivity, leading to current leakage. Or, when the sample is insoluble in water, it may be suspended, vortexed, and then centrifuged. The analysis is then performed on the supernatant as the ions are water soluble. 

Since AAS is a ratio method, many instrumental errors (e.g. long-term source drift, small monochromator drifts) should cancel out, as 7 is ratioed to I . However, a stable uptake rate, or aspiration rate, is required. This falls as the viscosity of the solution sprayed is increased. Nebulizer uptake interferences can be minimized if the dissolved salts content of samples and standards is approximately matched. For example, when determining pg cm sodium levels in 2 M phosphoric acid, ensure that the standards are also dissolved in 2 M phosphoric acid, using a blank to check for contamination. 

Basic components of a spectrophotometer include a radiation source, a monochromator, a sample cell, and a detector. To minimize errors in spectrophotometty, samples should be free of particles, cuvets must be clean, and they must be positioned reproducibly in the sample holder. Measurements should be made at a wavelength of maximum absorbance. Instrument errors tend to be minimized if the absorbance falls in the range A — 0.4—0.9. 

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