Frequency Modulation

For more quantitative results than phase detection or Amplitude Detection, use frequency modulation (FM). This technique provides a direct measure of the change in resonant frequency sensed by the cantilever.

Prior to initiating this procedure you must have completed the steps outlined in Basic EFM Operation.

1. Follow all the steps required to perform Phase Detection EFM.
2. In the Interleave panel, set the Input Feedback to Frequency.
3. Switch the Data Type for Channel 3 to Frequency.

NOTE: It may be necessary to optimize the FM gains in the Interleave panel to properly track the shifts in resonant frequency. Suggested starting values: Input Igain (integral gainThe multiplier of correction applied in response to the average error signal.) = 40 and Input Pgain (proportional gainThe multiplier of correction applied in response to the error signal in direct proportion to the error.) = 60.

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