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Free Air Amplitude in Tapping Mode

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meaton212 posted on Sun, Oct 16 2016 10:23 AM


I need to conduct some tapping mode experiments that require the knowledge of the ratio: A/A0 where A0 is the free amplitude of the cantilever oscillation in air, and A is the amplitude when in contact with the sample.

How do you find A0? I thought it was the drive amplitude, but that is described as "the amplitude of the voltage applied to the piezo system which drives the cantilever

vibration."  and not specifically as the amplitude of the cantilever in air, so now I'm not sure.




I am using a Bruker Dimension Icon system

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Verified by meaton212

You are correct - the drive amplitude is not the quantity you are interested in.

If you are tuning manually you can get the free amplitude by reading off the amplitude of the cantilever response (the blue curve on the upper graph in the tune window) at your chosen drive frequency (the position along the frequency axis that you set the "offset" marker to) - the value on the vertical axis at the point that the offset marker crosses the cantilever peak is the free amplitude.

If you are using auto tune, then the free amplitude is specified by the "target amplitude" setting, you can verify this by reading the amplitude off the tuning peak as described above.

Hope that helps.

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