It's due to its high precision.
Even pro riders have this kind of variation between their pedal strokes.
I've already posted this on the forum (viewtopic.php?f=35&t=78
), but I'll copy it here again:
The oscillations around the target power are normal during the training. Those oscillations are due to the power variations between one pedal stroke and another and they happen to any cyclist (even professional cyclists have the same behavior, although with lower amplitude variations).
These oscillations are therefore real. Following, a graph that shows a comparison between the power measured and displayed by the Drivo and the power measured with an ergometer:
You could think that the oscillations are due to the trainer resistance variations, but they aren’t.
The continuous variations of the resistance done by the trainer motor are necessary to adjust the brake to the microvariations of the cyclist speed (indeed, on varying of speed, the brake must be adjusted to keep the power constant).
We have verified that the same kind of oscillations occur even if the brake is blocked, and this demonstrates that the oscillations are intrinsic to the pedaling and are not due to the trainer behavior.
However, we are working on some trainer parameters to improve this aspect.
The differences between the pedal strokes are due to the cyclist and don’t depend from the training mode. Below you can see two charts related to two different training modes: Erg mode and Simulation mode; the registered power is compared to the power measured by a SRM ergometer during the two trainings. The charts show clearly the power variations between the pedal strokes (that is the difference between the power value of one pedal stroke and the following one). These values are almost identical in the two training modes and they are very close to the SRM measurements.
We’d like to point out that some programs can modify the power data, smoothing it to give a more pleasant visualization. In these cases, only the displayed data is modified while the developed power remains the same.
However, if a user prefers to see a more smoothed value it is possible to use the Drivo smoothing option in the advanced setting of the app.