Series of measurements
A measurement series is a larger number of measurements in which only one parameter changes or is changed at certain intervals .
Examples :
- In a series of measurements to determine the activity of an enzyme , the substrate concentration is increased at defined time intervals ( see enzyme kinetics )
- When observing a newly appeared comet , its location under the stars is measured several times a week and an exact orbit in space is derived from this.
Special cases :
Time series: With some measurement series the external circumstances vary - e.g. B. over time - so that the measured values change as a result (and not via the parameter).
Examples: temperature curve of a day, precise survey data in geodesy .
planning
- Establishing the conditions that must be kept constant so as not to affect the individual results in an unpredictable manner.
- Determination of the start point and end point of the size that is to be varied.
- Determining the way in which this variable is changed (e.g. linear increase by the same amount or exponential increase through doubling, see growth )
- Definition of the measurement method and type of registration (visual reading, electronic counting, etc.)
- Define how often a measurement series is repeated in order to be able to eliminate or determine statistical errors .
- Switching off systematic errors (e.g. preventing uncontrolled heat exchange through insulation when temperature changes are to be measured)
Presentation of the measurement results
A series of measurements is usually displayed graphically. (There is also an acoustic implementation, e.g. in neurophysiology or when measuring radioactivity ). This results in discrete measuring points in a two-dimensional coordinate system.
- If two parameters are observed at the same time, three-dimensional coordinate systems result. If even more sizes are taken into account, other modes of representation ( polygonal lines ) are also used.
For better illustration, these measuring points are connected to one another by lines or related to one another by means of compensation lines. However, it must be noted that the behavior of the system between the measuring points is not known. So the line is just an interpolation and therefore an interpretation .
evaluation
- The results of the repeated series of measurements are statistically filtered by error calculation so that “outliers” can be eliminated and the mean value and scatter calculated.
- If possible, the measurement curve obtained in this way is used to create a mathematical model .
- The evaluation can lead to the planning of new series of measurements or to repeating the series of measurements if errors were discovered or the accuracy was insufficient.
Literature (exemplary)
- Günter D. Roth : Observing planets. Practical guide for amateur observers and those who want to become one. 5th edition, ISBN 978-3-8274-3100-4 , Springer-Verlag 2002.
- Erwin Gigas : Physical-geodetic measuring methods. Dümmler-Verlag, Bonn 1966.