Reliability, measurement instruments

Thermal contact sensation by means of some reliable measuring instrument opens new ways for the optimization of this relatively new fabrics-surface characteristic, which often presents a factor that influences the choice of... 

Finally, for situations in which it is not clear that exposure is and will continue to be below the limit values, a detailed survey with a measurement strategy is required. The methods used are based mostly on instruments for sampling the environment in order to obtain reliable measurements of workplace air concentrations. In general, the measurement strategy must consider the most efficient use of resources for the purpose of obtaining quantitative data on exposures by having a clear idea of what the data will be used for or whether it meets the specified need. For example, if the data pertain to peak exposures, these peaks have to be assessed according to the STEL requirements, if any. 

Mechanical manometers are the oldest, simplest, and most reliable pressure measurement instruments. They have some disadvantages, which is one reason the use of electrical manometers is expanding. Their simplicity and fundamental nature can, however, be an advantage. 

Lack of reliable measurement is the first reason, as reliable ground-based measurements by scientific instruments have been made just in this century. These measure conditions only at the location of each instrument, and they are usually land-based, although 75% of the Earth is covered with water. We have been able to take precise, direct measurements only in the last four decades, and not until the advent of precision space borne instruments in the 1970s were we able to measure global temperatures at a range of altitudes across the entire atmosphere. 

In addition to the clinical interview, psychometric rating instruments allow for rapid and reliable measurement of the nature and severity of depressive and associated symptoms. 

The aim of this chapter is to give the reader a good understanding of the instrumentation necessary to carry out reliable measurements. Only the principles will be described and the reader is referred to more specialized books or reviews for further details (see Bibliography at the end of the chapter). 

Modem instruments will give reliable measurements for o values greater than about 0.1 p.A. Figure 4.8 shows that for the Fe +-Fe + couple, o 100 p,A... 

Reliable laboratory instrumentation is required to guarantee the safety of food products and enforce government regulations. Two main types of commercial instruments are available. One uses chilled mirror dew-point technology, while the other measures relative humidity with sensors that detect changes in electrical resistance or capacitance. Each has advantages and disadvantages. The methods vary in accuracy, repeatability, speed of measurement, stability in calibration, linearity, and convenience of use. 

The on-line measurement of viscosity under plant conditions poses particular difficulties. This is due to the wide range of viscosities that can occur within a process plant, to the difficulty of obtaining reliable measurements (particularly for non-Newtonian fluids) and to the accuracy that is often required (e.g. better than within 1 per cent for lubricating oils). Variables which can affect the measured viscosity are the temperature, pressure and rate of flow of the sampled stream— quite apart from the normal errors that can occur in any similar instrument (e.g. due to variations in supply voltage and frequency, sample contamination, sample not being representative of the bulk fluid, etc.). Automatic temperature compensation is always required and, in the case of multiphase systems, the difficulty of obtaining a representative sample is considerable (see Section 6.9). In this instance... 

It is useful to give a brief overview of some of the major advantages and limitations of ultrasound as a tool for characterizing the properties of food materials. Ultrasound is fairly inexpensive to purchase and operate, it is robust and can therefore be used in factories, it is capable of rapid and reliable measurements, in a non-destructive and non-invasive manner. In addition, measurements can easily be automated and so the technique is suitable for on-line measurements as well as an analytical instrument in the laboratory. The major disadvantages... 

Hayward et al. (2002) demonstrated that PTR-MS could reliably measure a wide range of VOCs and with a time resolution sufficiently fast to capture the dynamics of many environmental processes (e.g., the light dependency of isoprene emissions from vegetation). They also demonstrated that the components of the instrument output (signal plus noise) were easily characterized, enabling a simple interpretation of measurements. 

The numerical value of every observed measurement is an approximation, since no physical measurement—of temperature, mass, volume, etc.—is ever exact. The accuracy of a measurement is always limited by the reliability of the measuring instrument. 

Analytical methodologies and measuring instruments are the tools for obtaining reliable data on the composition of the material objects being studied. The science of the construction and operating rules of measuring instruments is often referred to as instrumentation. The successive stages in the development of this science are easily discernible. 

The range of scan angles through a pixel is also crucial in determining the ability of a given experiment to make reliable measurements of polarization. Observing the same pixel with different orientations of the instrumental axes provides the data needed to separate true celestial polarizations from instrumental effects. 

All three chromatographic techniques—GC, LC, and SFC—have been combined with MS and with IR. Not all have been equally developed, and none has yet reached the reliability of GC/MS. Additional combinations are possible, and chromatography will probably be combined with other measuring instruments in the future. 

As already discussed above, Q-ICP-MS may still require matrix removal and preconcentration because the Q mass analyzer is unable to resolve most of the spectral interferences affecting the analytical masses of PGEs. Moreover, the detection power might be inadequate for the performance of reliable measurements in some samples. PGEs determination is hampered by mass interferences and requires high analytical selectivity and sensitivity. Double-focussing SF-ICP-MS with mass resolution capabilities higher than those afforded by Q instruments (currently up to 10,000) can properly deal with most mass interferences that have... 

Although the mechanism for the production and deposition of acid are not yet fully understood, atmospheric chemists and meteorologists have been studying these problems in depth for the past several years and have made considerable progress. Methods and instruments for reliable measurements of key species in air and clouds have been developed and exploited in field studies. Rates of reactions important in the formation of acids, sulfates, and nitrates have been measured. Huge amounts of reliable field data have been accumulated. Models have been developed and are being tested against bodies of field data. 

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