Calibration
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The plot calibration means to make the plot coordinates to be the same as in the background image.
Calibration is performed with the following steps:
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Load the background image if not already done.
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Insert a rectangle, and resize/align it with the known axis coordinates.
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Zoom in as max as possible, to show one of the rectangle corners.
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Adjust the corner to the known background image values for x and y at this first point. Make it fit as exactly as possible.
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Scroll to the opposite corner.
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Adjust the corner to the known background image values for x and y at this second point. Make it fit as exactly as possible.
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Click on Tools Panel, Calibration.
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Set the 'x' Min and Max values for the 'x' axis that are present in the background image. Check the box if the 'x' axis is logarithmic.
- Set the 'y' Min and Max values for the 'y' axis that are present in the background image. Check the box if the 'y' axis is logarithmic.
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The current coordinates in the green strip will change to black and will be expressed in physical values, with subfix.
The plot can be re-calibrated at any time if necessary, and will be saved if the selected save format is *.ner.
After Calibration, the calibration rectangle can be deactivated (make it not visible) in the traces list.
All the created or generated plot traces depend on the exactitude ot this calibration. The exactitude may vary, depending on the quality of the background image, the position of the calibration rectangle and the uniformity of the scales. Typically, the exactitude is about 0.3 %
If the axis are not perfectly horizontal or vertical, the background image can be rotated using image processing.