Working Range Scaling (Span Scaling)
The redistribution of the full movement of the control element between the taught lower and upper limits. On the GS740-3P, once the upper limit is taught, the potentiometer rescales the span between idle and the taught upper speed as 0 percent to 100 percent. In this way no part of the lever is spent on an unused region.
Without scaling, the system uses the raw mechanical stroke of the actuator. If your engine actually uses only a section in the middle of that stroke, the beginning and the end of the potentiometer are useless. The rescaling done after teaching removes these dead zones.
The mathematics is linear: the lowest value of the control input is mapped to the idle position and the highest value to the taught upper limit; the values in between are distributed proportionally. On the GS740-3P the control input is a 0–3.3 V ratiometric potentiometer signal.
The practical result works both ways. On the positive side, adjustment resolution increases because the whole lever becomes usable. The point to watch is that the narrower the upper limit is chosen, the more compressed the scale becomes; a range narrower than necessary turns even a small drift of the potentiometer into a noticeable speed change.
Context in which this term is used: Electronic speed and throttle control on diesel engines