Simultaneous measurement
Simultaneous (simultaneous) measurements at different positions or with different instruments play a major role in natural sciences and technology . The purpose of such measurements is usually to eliminate sources of error. In detail, this can include:
- Investigation of changing environmental influences - most often the temperature
- Detecting systematic errors
- Influences of the observer and the measurement method
- Influence of various measuring instruments and optical-mechanical influences
- Elimination of constant quantities
- Elimination of errors in the time system .
Simultaneous processes are of particular importance wherever high relative measurement accuracy is required . The higher the accuracy, the more disruptive effects occur. They either have to be rendered harmless or they have to be modeled mathematically and physically.
Geodesy and Astronomy
Nowadays, in the fields of geodesy and astronomy , accuracies of 1: 1 million and more are required. For this reason, a number of simultaneous measurement and determination methods have been developed on the most varied of levels:
- simultaneous reading at different points of a measuring instrument - what z. B. Reduced temperature and vibration effects
- Reading or mirroring of opposite points on partial circles - which eliminates the eccentricity between circle and axis (see also double circle - theodolite )
- Mutual simultaneous measurements of the zenith distance between two points, which increases the accuracy of precise height measurements by 2–3 times
- Simultaneous or almost simultaneous measurement of stars on symmetrical sides of the sky - which eliminates refraction and telescope bending and greatly reduces personal or instrumental measurement errors
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Stellar triangulation - the simultaneous measurement of high targets from two points of view, whereby exact planes can be spanned and long distances can be bridged (see also satellite photogrammetry )
- Takes place simultaneously instead of only relative an absolute orientation of the measurements - directly in the coordinate system of the fundamental stars
- Simultaneous measurements according to stars or satellites in navigation and astrometry.
Examples from other subject areas
photography
In photography and photogrammetry it is also predominantly measurement of geometrical sizes. Therefore, similar methods as above are in use.
In navigation : Simultaneous measurement of the transit times of different radio waves - for example with LORAN , Decca and Global Positioning System .
physics
- Opposing light rays and their interference
- opposing orbits of elementary particles , overlays, collisions etc.
- Synchronization of physical processes and time systems
Electrical engineering
In the data transmission , the pliers measurement : Two observe time-synchronized instruments such. B. sending a dial command in the ISDN and at the same time the arrival of the incoming call at the other end. Protocol translation errors can thus be identified.
chemistry
- Detection of correlations between structure and catalysis.
For example: only changes the electronic structure as soon as the catalysis begins, or the atomic arrangement on the catalyst also changes, e.g. B. partial reduction, expansion of the crystal lattice, pore effects.
- Measurement of the kinetics as a function of the temperature, partial pressure of the starting materials e.g. B. O 2 , CO etc.
- Correlations of near and long-range order effects with different methods, since the methods complement each other, e.g. B. Exafs / Xanes to determine the local structure (closest neighbors) and XRD to categorize the crystal system (long-range order effects, superstructures, statistical or ordered distribution of defects, vacancies, etc.)