Question about <device>.addSpringEffect

[Melody]

<device>.addSpringEffect( gain=None
,magnitude=None
,position=None
,referenceFrame=None )

First,According to the help in vizard, the magnitude of the effect force is capped at the value of the magnitude property. So what is the unit of magnitude. Is it N?

Also, how does this affect the spring force? The spring force is calculated using the expression F = k(P-X), so actually, the force is also multiplied by magnitude?

Third, anyone knows how to get the exact position of real-time haptic device? I tried to get the link position as well as the object linked to the device. Both do not work.