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The OAT Analog Tacho Process VI and the OAT Digital Tacho Process VI both return rotational speed as a function of time. These VIs employ a digital differentiator method to calculate the rotational speed from tachometer pulses. As the following equation shows, the OAT Analog Tacho Process VI and the OAT Digital Tacho Process VI calculate the rotational speed as the first derivative of the rotation angle:

where ω is the frequency and θ is the rotational angle.