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| Copyright by Gary Larson: The Far Side |
The height of the cantilever is kept constant:
Thus only the deflection is recorded and together with the spring constant the force is calculated.
Problem: The deflection of the cantilever is a little non-linear. The spring constant gets more incorrect the greater the deflection and thus the calculation of the force.
The vertical position is adjusted:
The feedback controller ensures that the force which is on the tip is kept constant. Thus the sample is adjusted in its vertical position. By this means the non-linearity of the cantilever is avoided.
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