Metrology system

Many countries have established national measurement institutes to oversee their metrology systems and obligations to the Treaty of the Metre. Sometimes chemistry and other sciences are separated (as in the National Physical Laboratory and the LGC in the United Kingdom), but increasingly chemical mea-... 

The Inter-American Metrology System (SIM) http //www.sim-metrologia.org.br/... 

In modern high-technology situations, however, very high reproducibilities are frequently required. A good metrological system must provide means whereby any measurement station can have access to the highest needed level of the system. 

The above sections have highlighted the importance of data comparability and trace-ability in the context of WFD chemical monitoring. Let us now examine in detail what references need to be considered for the development of a sound metrological system. Firstly, as a reminder, traceability is defined as the property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties (ISO, 1993). The ways in which these elements can be applied to chemical measurements were discussed some years ago (Valcarcel and Rios, 1999 Quevauviller, 1999 Walsh, 2000) and those discussions still continue. In this context the basic references are those of the SI (Systeme International) units, i.e. the kg or mole for chemical measurements. Establishing SI traceability of chemical measurements may, in principle, be achieved in relation to either a reference material or to a reference method (Quevauviller and Donard, 2001). The unbroken chain of comparison implies that no loss of information should occur during the analytical procedure (e.g. incomplete recovery or contamination). Finally, traceability implies, in theory,... 

An in-line inspection system is an integral part of the manufacturing system and therefore has to be included in the global cost and benefit analysis when evaluating the overall investment of the production faciUty. Besides the overall cost of the production equipment, the following economic factors specifically related to the metrology system should be included in the economic analysis (Kunzmann et al. 2005) ... 

Within a robust metrological system the values of measurement standards and measurement results are linked via comparisons or calibrations that take into account the measurement uncertainty of the linking... 

White light interferometry was employed to inspect the stamps and replicates used in this research in device fabrication. The Wyko NT3300 surface profiler is a commercially available inspection system equipped with hardware and software for data acquisition and analysis (www.veeco.com). The metrology system has 0.1 nm resolution in the vertical (z) axis. Laterally, in the XY plane, resolution is dependent on the pixel size in each scan. Thus, the objective and field of view of the scan determines lateral resolution. Scans in this study were performed using 20.8x effective magnification, translating to 0.7 pm pixel size. Considering the size scale of the structures involved, this lateral resolution was... 

Metrological attestation as the procedure that ensures reproducibility and comparability of the results of measurements is specified in GOST 8.010-90 State System of Measurements. Procedures of Measurements Implementation didn t find wide use in NDT. In airspace industry, railway and naval transport the requirements of approval of test procedures is in force more than 20 years. In chemical and oil-chemical sectors the similar requirements were less explicit. In some industries, for example in building GOST 8.010-90 was not put into account. 

Process measurements encompass the apphcation of the principles of metrology to the process in question. The objective is to obtain values for the current conditions within the process and make this information available in a form usable by either the control system, process operators, or any other entity that needs to know The term measured variable or process variable designates the process condition that is being determined. 

Qualitative analysis methods should have well-grounded and generally adopted quantitative reliability estimations. At first the problem was formulated by N.P. Komar in 1955. Its actuality increased when test methods and identification software systems (ISS) entered the market. Metrological aspects evolution for qualitative analysis is possible only within the scope of the uncertainty theory. To estimate the result reliability while detecting a substance X it is necessary to calculate both constituents of uncertainty the probability of misidentifications and the probability of unrevealing for an actual X. There are two mutual complementary approaches to evaluate uncertainties in qualitative analysis, just as in quantitative analysis ... 

The simplest calibration procedure for a gas flow-measuring device is to connect it in series with a reference meter and allow the same flow to pass th tough both instruments. This requires a reference instrument of better metrological quality than the calibrated instrument. One fact to consider when applying this method is that the mass flow rate in the system containing both instruments is constant (assuming no leakage), but the volume flow rate is not. The volume flow rate depends on the fluid density and the density depends on the pressure and the temperature. The correct way to calibrate is to compare either the measured mass... 

The key difference between a CRM and an RM is the traceability. In order to play any role at aU in metrology, traceability is a key property. Traceability refers to a property value of the CRM, and thus to the underlying measurements. Insufficient traceability of these measurement results will eventually lead to a RM that cannot be certified, as the property value cannot be related to other standards. In the ideal case, traceability is realized up to the International System of Units, SI, but this is only feasible for a very small number of CRMs. 

It should be recognized that, in some cases, it is not difficult to set up a traceable measurement system. The best examples of this are in physical metrology where traceability is often based on direct measurements of the SI units. There is also general agreement that a similar SI fink is highly desirable in the case of chemical measurements, but, for a variety of reasons, direct chemical traceability is difficult to achieve in most of the analytical chemistry applications. Only a very few analytical chemistry procedures exhibit a direct measurement capability that allows the set-up of a traceable measurement pathway such as in physical metrology measurements most of these procedures have been accepted as primary methods if carried out under certain constraints (CCQM 1998). 

Installation qualification (IQ). IQ demonstrates that the equipment/system has been installed correctly at the user site according to vendor standards. The vendor should install the equipment to demonstrate to the buyer that all the components are operating properly. The qualification process includes appropriate documentation of the system components, physical installation and hook-up, and a performance check to verify that the individual components operate and can communicate with each other. System component information, such as serial numbers, type of use, and user performance requirements, should be included in the metrology database for easy tracking and scheduling of maintenance and/or calibration. 

In addition to incorporating the preceding elements into any metrology program, periodic audits of the calibration and maintenance practices should occur. This is particularly important for systems generating data that are subject to review by... 

Primary methods have the highest metrological qualities, whose operation can be completely described and understood, and for which a complete uncertainty statement can be written down in terms of SI units. Such methods are used by national laboratories participating in the development of a national or international chemical measurement system. 

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