Introduction
Performing measurements is a process similar to an industrial production process. There are several phases to be observed. In each of these phases specific information is needed. The information is sometimes for the sake of the process itself, however in most cases the information has to be passed to the next phase. Items like purpose, identification, reliability and accuracy have to be addressed and have to be secured. In each phase one must be able to observe the process, see what has been produced, evaluate and visualise results. For simple and incidental processes these actions can be performed manually. As an ad hoc solution data is read into a spreadsheet programm and -when needed- graphs are drawn. When the process becomes more complicated and when a series of measurements has been performed, a more structural solution is needed, where checking and controling the process can be done semi-automatically.
The phases
As a paradigm we distinghuish five phases.
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5 Filing is the phase were the results of the measurement and the analysis are stored. The results are frozen, and stored in an archive or a database. Maybe some information about storing the file can be added, however this is not the kind of information which adds value for industrial or scientific purposes. Usually the moment in time when the results have been filed and who has filed them is added to the data.
The process in detail
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Even before a data acquisition system is running, we must collect data, in order to secure how we performed an experiment and what the readings mean. The questions we must ask are:
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Static information, like calibration coefficients, ambient conditions and material properties are added as GEF keywords, basically in the flavor Measurement and Specimen. If any of this information is changing in time, it should be added as variable information in the data section of a GEF file.
Analysis
In the next phase we have to deal with the analysis of the recorded data. For measurements that are commonly performed, usually a norm or a standard exists, issued by organisations like ASTM, BST, DIN, NEN, ISO. If the results of the measurements are to be analysed according to such a standard, we can add this information to the recorded data: (to be) analysed according to NEN ####. This information can be either derived from the way the experiment has been performed or should be added. Not just the type of measurement (permeability), but the particular way (standing or faling head) has to be added as well.
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Static information, like permeability, cohesion, thermal expansion, can be stored in GEF keywords with the flavour Analysis. Non static information is added as columns in the data block of a GEF file.
Filing
During filing just administrative data is added, stating on which date the results are frozen or stored in a database. Who has stored them? Where in the database are the results stored? The latter is quite important since there should exist only one instance of a measurement. This information is stored as GEF keywords of the Filing flavor.
Report
The type of report one can produce depends on the needs of the client. A consultant or engineer is content with a number, characterising the strength of a material. A researcher might have ideas for a better analysis and so he wants all data. When writing a report for a client, a table of all derived results is needed, and may be graphs of the derived quantities as annexes. The amount of space in a scientific journal imposes yet other needs: a graph with all data, underlining the point or thesis of the article.
The results produced int the report phase differ a lot. A graph may be an image file suitable for a website, a table may be a file suitable for a text document. Sometimes a data or a selection of the data can be transfered to the client. When using standardised software, static information how the data should be (automatically) presented or visualised may be added, als GEF keywords in the Report flavor.
Overview
During the first three phases the amount of information in a GEF file grows. We start with a basic measurement file. The data acquisition system and tailored measuring software provide basic information about the quantities that are recorded. Additional information about transducers, measuring procedures and sample have to be added separatedly. During analysis more information is added. This consists of both static information for derived quantities (like a thermal expansion coefficient) and non-static information, such as columns of translated (physical units) transducers (like effective stress). During analysis the size of a GEF file may double or tripple. Adding filing information does not alter the size of the GEF file significantly, usually its size increases less than 1 kilobyte. When reporting the amount of data usually diminishes. The columns with the raw data in non-physical units are removed, intermediate results are less interesting, a section of the data is selected etc. Some information may be added, however not of scientific or industrial importance, like the number of the annex to be drawn, the line width or line color in a graph.
Implementation
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General
A successful implementation of this methodology depends on the possibility to perform quality control in each of the four phases. A major advantage of using the same format in all phases, e.g. GEF, is that one can use the same applications and software to visualise results in all phases. Furthermore during analysis one can use the same basic library functions as have been used for the visualisation of GEF data. Reading a file, either measurement, analysis, filing or report, remains the same. The amount of data to be read may vary, the method isn't. Another advantage is that one can develop generic and sometimes highly specialised methods to analyse data. Since these functions can be reused for other projects, the balance between yield and effort can be tipped towards yield due to improved efficiency.
We use GEF for the storage of measurements, their analysis and we use GEF to report results to our clients. A database for filing the GEF files is curently (July 2006) under construction. While the measurements are running, we use software to monitor the signals of the transducers. Furthermore, when clients ask for it, we provide a nearly realtime presentation of the experiment on the World Wide Web, by means of graphs which are derived from the data in the GEF file of the current test. The state of the equipment, like temperatures of bearings, stresses in rotor arm, the air pressure in the setup etc, i.e. quantities which are needed for running the experiment safely, is monitored as well by the same software as for visualising the results of the measurement. This allows for the first and rough quality control of the data. When the data is analysed, new quantities are dervied and added to the GEF file. The same software as used for monitoring the experiment can now be employed, to visualise the derived quantities. Finally, when the client wants to do an analysis of his own, the client can use the same software as we used for monitoring his experiments, and get the first impression of the results. Additionaly tools for the conversion from GEF to other formats, e.g. a Excel spreadsheet, are available.
Examples
An very nice and convincing example of the way GeoDelft has implemented this methodology for a series of centrifuge tests can be read in this pdf document, This document is made available by the courtesy of Samsung JV. GEF has been used for the purpose of exchanging information between phases and to the client. This implementation has been proven to be successful, since all necessary information of the experiment is either present in the files or can be retrieved, using the information provided in the files.
Another example of a successful implementation can be found in the phases of a series of tests on micro instability, which were preformed in 2004. The document which describes the different phases is not as spectacular as the previously mentioned pdf document, however the accompanying data are not disclosed. Therefore we illustrate the use of phases by means of files of the micro instability test. Results of these tests have been published on the ICPMG conference of 2006. All files of test 5 have been compressed into a ZIP file.
The following actions have been done during the four phases:
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