Reference measurement

Experiments have shown promising results. For components in sintered state a number of components with different defects have been able to reject based on reference measurements on components without defects. For components in green state the results vary, cracks have been able to detect, but density differences not. For both measurements on components in green and sintered state scatter between measurements was observed to be substantial. 

Practical applications of SR-TXRF currently focus on fast mapping of wafers up to a diameter of 300 mm and reference measurement capabilities in the range of 10 -10 atoms cm [4.58]... 

If relative sensitivity factors are used, reference measurement of standard samples is not necessary. The ratio of two different elemental concentrations in one sample is given by ... 

McQueen MJ, Roberts HR, Siest G (1995) Reference materials and reference measurement systems in laboratory medicine - a major international meeting organized by the International Federation of Clinical Chemistry (IFCC), Geneva, October 5-7, 1994. Europ J Clin Chem Clin Biochem 33 977-999. 

Environment A number of melt water quality analyses of heavy metals, hydrocarbons, oxygen demands, and nutrients were made. From September 2001 to September 2002 measurements were made in the snow storage, in the stream where melt water is discharged and in the recipient, totally at seven locations. Reference measurements were made at a nearby location not affected by the outlet water. The results were compared with Swedish environmental quality criteria (SEPA, 1990 SEPA, 1999). 

The determination of the amounts of analytes can be based on absolute, relative or reference measurements (Hulanicki [1995]) which are based on equations of the general type... 

Direct reference measurements by the relation of measured value to content (concentration) of a reference material (RM)... 

On the other hand, indirect reference measurements are based on empirical calibration functions obtained experimentally and frequently based on Unear models... 

In the simplest case, experimental calibration can be carried out by direct reference measurements where the sensitivity factor b is given by the relation of measured value to concentration of a reference material (RM), b = yRvi/xRv,. Direct reference calibration is frequently used in NAA and X-ray analytical techniques (XRF, EPMA, TXRF). 

On the other hand, indirect reference measurements which result in an empirical calibration function, frequently based on a linear model, y = a + b - x + ey see Sect. 2.4, Eq. (2.22), where the intercept a corresponds to... 

In analytical practice, some methods using definitive measurements, in principle, are also calibrated by indirect reference measurements using least squares estimating to provide reliable estimates of b (spectrophotometry, potentiometry, ISE, polarography). 

Depending on the type of instrument, the reference measurement (top diagram) might be made simultaneously with the sample measurement (bottom diagram) or a reference measurement might be saved on computer to generate the full spectrum. 

Because of aging, it is necessary to specify an age for reference measurements at which the capacitance shall be within the prescribed tolerance. This is traditionally fixed at 1000 hours, since for practical purposes there is not much further loss of capacitance after this time. 

Fig. 2. Hand-held configuration of the FieldSpec 3. with the author taking a reference measurement.

Figure 6.2 X-ray diffraction identifies phases in a manganese-promoted iron Fischer-Tropsch catalyst after reduction (middle) and after CO hydrogenation or Fischer-Tropsch synthesis bottom). The spectra show that Mn is present as slightly distorted MnO (see the MnO reference measurement at the top), and that bcc iron (peak at 2 6 = 57.0°) converts to iron carbides (peaks around 55°) during the Fischer-Tropsch reaction (from van Dijk et al. [7]).

References. Because the detected fluorescence signal is a direct response of the dye-analyte complex formed, no reference measurement is required. Also no calibration of the probe is required, although the response function of the probe may be needed. 

Diode-array spectrophotometers have no moving parts, or at most a shutter that moves thus they are more suited to locations near the process. However, these instruments still require the introduction of the sample into the instrument s sample cavity, as well as the necessity for a separate reference measurement. These instruments are usually only found in a single-beam configuration. 

Alternatively, for nonequilibrium process streams, where a pumped reactor sample recycle line is available, in-line fiber-optic transmission cells or probes (Figures 5.26 and 5.27) can be used to minimize sample transport. It is highly desirable that some form of pumped sample bypass loop is available for installation of the cell or probe, so that isolation and cleaning can take place periodically for background reference measurement. 

Sample mass mass reference - measurement unit... 

There are two disadvantages with this method. On the one hand much effort is required to ensure the accuracy of the reference measurements. This is a matter of capacity in the reference laboratories and a matter of costs as well. On the other hand there might be doubt among the participants about the assigned value, because nobody is perfect . This is especially true if the mean of the participants results deviates from the assigned value. 

Very much effort to ensure the accuracy of the reference measurements... 

It is an important feature of the new business model that invoicing is not carried out by kg or I of auxiliary material but that other reference measurements are necessary. 

FIGURE 5 Relationship between sampling rate and effective resolution of process capability assessment. The curve is based on the width of the confidence intervals for estimation of mean and variance. The relationship shown does not consider the effect of reference measurement precision, which would further reduce the ability to discern changes in process capability. 

In the present study we investigated energy transfer between the Zn-porphyrin units in a sequence of dendrimers varying in size from 4 to 64 porphyrin units (Fig. 1). Reference measurements were performed on the monomer, P1D1. In order to follow energy transfer within the dendrimers, the fluorescence anisotropy decay were analysed. To determine the lifetime of the dendrimers, additional analysis of the kinetics measured at magic angle was performed. The fluorescence anisotropy is defined by... 

Type of Flowmeter Reference Measures Volume or Mass Flow Oases or Vapours Steam Liquids Slurries Operating Temperature of Sensor [Pg.440]

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