1.4.2 Graphic interpretation
Graphic interpretation is used to expressing the relationship between physical quantities and also to get a simple analytical function formula by drawing geometric lines with a series of corresponding measured values on graph paper.
1)Benefits of plotting
Plotting is often used in experimental data processing.The benefits are as follows:
(1)The function relationship can be displayed intuitively,and certain experimental results such as slope and intercept can be found directly in the line chart.
(2)Corresponding values that are not measured in the experiment can be obtained from the line chart with interpolation and extrapolation.
(3)Some data with flaws can be found in the graph.
(4)A standard data curve of the instrument can help not only correct systematic errors but also speculate other measurement values.
2)Requirements of plotting(https://www.daowen.com)
(1)Select suitable coordinate paper such as rectangular coordinate paper,logarithmic coordinate paper and polar coordinate paper.
(2)The size of coordinate paper and the scale of coordinate axis should depend on the significant figures of measured data and requirements for precision of results.In principle,the minimum gird of the coordinate paper is limited by the last significant digit of experimental data,which gives proper enlargement a shot to become possible.Though the origin of coordinates being outside the graph makes sense,it would be better to have the graph in the middle of the coordinate paper.
(3)The physical quantities,units and division values should be marked on coordinate axis.
(4)Symbols such as+,X,△,and⊙are used to mark data points on coordinate paper,while identical symbols are used on the same curve.
(5)The curves are supposed to be smooth during connection.Particularly,the calibration curve should involve all calibration points.It is not strictly required that all points need to be on the curve.But the deviation of the points from the curve should be more evenly distributed on both sides.Figure 1.4.1 is an example of graphic interpretation for the relationship between current I and voltage U.
Figure 1.4.1 The relationship between current I and voltage U
