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Acceleration to Velocity and Displacement Conversions on a 35670A Dynamic Signal Analyzer.

On the 35670, one can convert signals from an accelerometer to velocity and displacement readings.

Choose the FFT Analysis instrument mode. Press the Input key, press the XDCR UNIT CH1 SETUP softkey, turn XDCR UNIT ON, set XDCR SENSITIVITY to correspond to your transducer sensitivity, set the XDCR UNIT LABEL to your desired acceleration units (g, m/s^2, or inch/s^2).

Now set up your display: Press Measurement Data, choose Linear Spectrum Channel 1. Press Trace Coordinates, Y UNITS, XDCR UNITS CONVERT, then simply press velocity or displacement units.

Alternatively, you could create a math function that divides linear spectra by jw (j ohmega). Dividing the Fourier transform by jw once is like integrating in the time domain; you can transform from acceleration to velocity, or velocity to displacement.

Similarly you could divide linear spectrum by jw twice. This will convert acceleration to displacement. Note that you should use linear spectrum; I do not recommend using power spectrum -- since the units are squared, you have to divide by jw twice for acceleration^2 to velocity^2. These are very nonintuitive units; only use them if you must for some reason.

Of course, if you are converting time domain data, you can just use the integration operation when you define your function instead of dividing by jw.

Refer to the built in help screens for detailed descriptions of each of the math functions.