Precision measurement units

The measurement units of each parameter give a preliminary indication of the nature of these parameters, but for a more precise idea of their chemical and physical significance the reader is referred to the literature7-9. In the present context it is sufficient to bear in mind that most of these empirical parameters can be subdivided into parameters which measure the Lewis acidity (hence, the electrophilic power) and Lewis basicity (hence, the nucleophilic power) of a solvent. 

Presentation of the confidence interval facilitates evaluation of the reported data in original measurement units, which simultaneously incorporates the statistical changes observed and the precision of the measurements in the units in which the data were measured. The confidence interval provides a bridge to clinical importance, in that the reader can see the observed experimental change in the context of a range of uncertainty in the same units. Indeed, for this reason, the reporting of confidence intervals is required by many periodicals. 

Diffractometer software can search for reflections, measure their precise positions, and subsequently compute unit-cell parameters. This search entails complexities we need not encounter here. Instead, I will illustrate the simplest method for determining unit-cell dimensions measuring reflection spacings from an orthorhombic crystal on a precession photograph. 

In daily life, the use of suitable measurement units enables us to evaluate quantities more precisely. Instead of requesting 123 cherries from your grocer, isn t it easier to ask him for a desired quantity in kilograms Or, instead of packets of sugar, would you rather ask for 240 lumps in a supermarket (Figure 1) ... 

We have developed the CMP Semi-InSitu Monitor and confirmed that it is capable of highly precise measurements. This system incorporates a compact measurement unit composed of a small optical head, wafer rinse nozzles and an R-6 stage. Since measurement is performed while the wafer is still held in the CMP top ring, it can be immediately returned to the table for further polishing if necessary. 

Note that the standard deviation has the same units as the data, while the variance has the units of the data squared. People who do scientific work tend to use stan-dai d deviation rather than variance as a measure of precision. It is easier to relate a measurement and its precision if they both have the same units. The advantage of using variance is that variances are additive in many situations, as we will see later in this chapter. 

A measurement is always reported as a value, a quantitative description that includes both a number and a unit. For example, before a 100-meter race is run, the distance must be measured as precisely as possible. Its value is 100 meters. In this value, the unit is meters (defined below), and the number of units is 100. 

The redox potential is pH-sensitive and should be measured in conjunction with pH. To convert redox potentials to a common pH, the conversion factor of —59 mV per unit pH is usually employed, although the change of redox potential with pH can be as great as —200 mV per unit pH during rapid redox changes. The value of —59 mV per unit pH is probably reasonable for most measurements. Reporting both the measured redox potential and the pH avoids the conversion problem. Because redox potentials are most often mixed potentials, measurements more precise than 10 mV have little significance... 

One simple qualitative test method is the scotch-tape test. In order to carry out quantitative measurements, however, more precise methods have to be used and existing commercially available measuring units are of use. Some of these methods are discussed in detail in the following sections. Additional information can be found, for example, in [105]. 

There is no generally-acknowledged method or measuring unit to specify the extrusion behaviour of ceramic bodies. In order to obtain an adequately precise description of the extrusion behaviour, numerous specific methods do exist, which have to be chosen according to the material, for example for bodies to produce bricks and tiles or bodies for the manufacture of catalyst converters, as well as methods relating to specific application requirements, be it for example for the purposes of production, quality control or development of the body. 

The concepts of precision and resolution (sensitivity) are often confused. While resolution represents the smallest measurable unit that can be read, precision is the smallest measurable unit that can be read repeatedly and reliably. Consider the difference between a digital chronometer with a resolution of 0.01 s and an analog stop watch with tick-marks at intervals of 0.1 s. The total measuring system not only includes the chronometer but also the person using it. Since the... 

The electronic caliper shown in Fig. 6.8 is a modern-designed precision measuring instrument which has an electronic measuring unit with an LCD digital readout giving direct readings in imperial or metric units with a resolution of0.0005" or 0.01 mm. 

The aim of the quantitative analysis is to measure an amount of radioactivity in either a relative or absolute sense. Common units are Becquerels (Bq), Bq per unit mass or Bq per unit volume. In special cases, the activity is expressed as a mass of the radioactive nuclide. The determination of absolute activity presents special problems in addition to those encountered in relative activity measurements. Once a source of a radionuclide of known absolute activity is available, any detector may be calibrated in terms of this standard. This calibration will be valid for other samples of the same nuclide, provided they are measured under precisely the same conditions. The calibration may also be adequate for other radionuclides emitting radiation similar to those of the standard. 

Historically, many societies required that measuring devices be physically compared with and calibrated against official standards. Physical representations of measuring units were made as precisely as possible and carefully stored and maintained to serve as standards for comparison. In ancient Egypt, the standard royal cubit was prepared as a black granite rod and most likely kept as one of the royal treasures by the pharaoh s chief steward. That simple stone object would have been accorded such a status because... 

How do Geiger counters and scintillation counters measure radioactivity Precisely, what do they count Do they count radiations or do they count something that is proportional to radiation Suggest units for radioactivity as it would be measured by either of these counters. 

The International Bureau of Weights and Measures located at Sevres, France, serves as a permanent secretariat for the Metric Convention, coordinating the exchange of information about the use and refinement of the metric system. As measurement science develops more precise and easily reproducible ways of defining the measurement units, the General Conference of Weights and Measures—the diplomatic organization made up of adherents to the Convention—meets periodically to ratify improvements in the system and the standards. 

The connection between mass and volume, and thus also length, was the most difficult branch of metrology. Hundreds of units have been described, each pointing to a different method of dilatometry. Once one establishes the basic unit, which today is naturally the SI unit meter (see Fig. 2.16), measurement involves precise subdivision and comparison. 

In the newly developed units, the dynamometer is mounted together with the high-precision electronic torque-measuring unit on a stable and distortion-free base plate. The torque of the linear dynamometer is measured directly using a load cell without any intermediate member, thereby increasing the overall reliability of the torque rheometer. 

The numerator in the Odor Unit is the odorant coneentration, whieh can be measured very precisely. Techniques such as isotope dilution... 

This is a complete system of measurement units including names and symbols for base units from which derived units may be formed so that any physical quantity may be expressed. It includes a system of prefixes by which the base and derived units may be made any convenient size from very small to very large. Finally, the precise basis for its units, and the symbols for expressing them, have received worldwide agreement. It is officially recognized by all industrial nations, is referenced by SAE, ASTM, ASME, and many other societies, is required by ISO in all documents, and is the official basis of our U.S. units (the inch and pound are defined in terms of the metre and kilogram). 

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