Embodiments of the present invention provide apparatus and methods for supporting, positioning or rotating a semiconductor substrate during processing. The actuator or actuators are controlled with different pulse-width modulated control signals, whereby the pulse-width and the cycle duration of the control signals can be adjusted independent of each other and are adjusted independent of the actually applied on-board power voltage. When executed by the at least one processor, the thermodynamic state solver application computes a flash equilibrium state solution for each of a plurality of nodes in a thermodynamic network and determines for each of the plurality of nodes at least one sensitivity of a first thermodynamic property with reference to at least one second thermodynamic property. A distance between the reflected image position from the at least three discrete light sources from both surfaces of the transparent sheet is used to calculate the thickness of the transparent sheet and the spacing between at least two transparent sheets.